syndrome
Titulaer, M.J.
Citation
Titulaer, M. J. (2010, November 24). Prediction of small cell lung cancer in the Lambert-Eaton myasthenic syndrome. Department of Neurology, Faculty of Medicine / Leiden University Medical Center (LUMC), Leiden University. Retrieved from https://hdl.handle.net/1887/16174
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CHAPTER 6
The clinical DELTA-P score accurately predicts small cell lung cancer in the Lambert-Eaton myasthenic syndrome
MJ Titulaer 1,2, P Maddison 3, JK Sont 4, PW Wirtz 5, D Hilton-Jones 2, R Klooster 6, N Willcox 2, M Potman 6, PA Sillevis Smitt 7, JB Kuks 8, BO Roep 9, A Vincent 2,
SM van der Maarel 6, JG van Dijk 1, B Lang 2, JJ Verschuuren 1,
1 Dep. of Neurology, Leiden University Medical Center, Leiden, the Netherlands
2 Neurosciences Group, Dep. of Clinical Neurology, John Radcliffe Hospital, Oxford, United Kingdom
3 Dep. of Neurology, Queens Medical Centre, Nottingham, United Kingdom
4 Dep. of Medical Decision Making, Leiden University Medical Center, Leiden, the Netherlands
5 Dep. of Neurology, Haga Hospital, The Hague, the Netherlands
6 Dep. of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands
7 Dep. of Neurology, Erasmus University Medical Center, Rotterdam, the Netherlands
8 Dep. of Neurology, University Medical Center Groningen, Groningen, the Netherlands
9 Dep. of Immunohaematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
We dedicate this paper in affectionate gratitude to the memory of John Newsom-Davis FRS (1932-2007), who contributed so much both to our understanding of the Lambert-Eaton myasthenic syndrome and to the UK cohort of patients.
Abstract
Introduction Approximately one half of patients with Lambert-Eaton myasthenic syndrome (LEMS) have small cell lung carcinomas (SCLC), aggressive tumours with poor prognosis. In view of its profound impact on therapy and survival, we developed and validated a score to identify the presence of SCLC early in the course of LEMS.
Patients and methods We derived a prediction score for SCLC in LEMS in a nationwide cohort of 107 Dutch patients, and validated it in a similar cohort of 112 British patients. A Dutch-English LEMS Tumour Association Prediction (DELTA-P) score was developed based on multivariate logistic regression.
Results Age at onset, smoking behaviour, weight loss, Karnofsky performance status, bulbar involvement, male sexual impotence and the presence of SOX1 serum antibodies were independent predictors for SCLC in LEMS. A DELTA-P score was derived allocating one point for the presence of each of the following items at or within three months from onset: age at onset ≥50 years, smoking at diagnosis, weight loss ≥5%, bulbar involvement, erectile dysfunction and Karnofsky performance status <70. The area under the curve of the receiver operating curve was 94.4% in the derivation cohort and 94.6% in the validation set.
A DELTA-P score of 0 or 1 corresponded to a 0-2.6% chance of SCLC, whereas scores of 4, 5 and 6 corresponded to chances of SCLC of 93.5%, 96.6% and 100%, respectively.
Conclusions The simple clinical DELTA-P score discriminated LEMS patients with and without SCLC with high accuracy early in the course of LEMS.
Introduction
Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder affecting the neuromuscular junction, characterized by proximal muscle weakness, loss of tendon reflexes and autonomic dysfunction.1 Antibodies are directed against P/Q- type voltage-gated calcium channels (VGCC).2 In 1956, Lambert, Eaton and Rooke3 first described an association with lung cancer. Small cell lung carcinomas (SCLC) are found in over half of the patients.1, 4-8 In those with SCLC (SCLC- LEMS), LEMS is initiated by an immune reaction to VGCC expressed on the surface of the SCLC.2 The resulting antibodies react with VGCC at the presynaptic nerve terminal of the neuromuscular junction causing the neurological dysfunction.
The remaining LEMS patients have no evidence of SCLC even after many years’
follow-up and cancer screening. These patients are thought to suffer from a non- paraneoplastic autoimmune LEMS (nontumour-LEMS; NT-LEMS).
An SCLC has a profound impact on therapy and prognosis. Therapy is focused on the tumour, and survival of SCLC is poor, whereas NT-LEMS patients are thought to have a normal life-expectancy. A diagnosis of LEMS prompts a careful search for an SCLC. Screening for SCLC by CT-thorax, FDG-PET and bronchoscopy is required, and as SCLC may be too small to detect initially, these investigations need to be repeated every 6 months for at least two years.9 With this approach, 96% of SCLC are found within a year of diagnosing LEMS,9 while a delay of more than two years is extremely rare; nevertheless, some patients undergo many procedures with associated anxiety and costs. Care would be improved if those who do require intensive investigations as well as those no longer at risk could be identified.
There are several factors that may help. Older age,1, 10 smoking,1, 11 development of multiple clinical symptoms within six months after onset,12, 13 raised ESR1 and SOX1 antibodies14, 15 all suggest the presence of SCLC. Its absence is suggested by young age, no smoking history, slow evolution of clinical symptoms and the 8.1 HLA haplotype.13, 16-18 However, it is not clear whether these variables are independent, nor which are most reliable. At present, none seems robust enough on which to base far-reaching decisions. We developed a prediction rule based on a combination of these variables that would distinguish SCLC-LEMS and NT-LEMS early in the course of the disease, with sufficient accuracy to guide clinical decisions. Two large cohorts of LEMS patients were studied to first derive the score and secondly to validate it.
Patients and methods
Derivation sample
We included all Dutch LEMS patients with and without SCLC seen between 1990 and 2006. Nationwide referral to the Leiden neuromuscular centre began in July 19988 and all patients alive at the time were investigated in a standardized fashion;
new cases were added prospectively.
The diagnosis of LEMS was based on characteristic clinical features of proximal muscle weakness, reduced tendon reflexes, autonomic symptoms and in addition either the presence of VGCC antibodies or characteristic features of repetitive nerve stimulation.1, 19 Repetitive nerve stimulation supported the diagnosis when it showed a low compound muscle action potential amplitude, combined with a decrement at low-rate stimulation and an increment of at least 100% following high-rate stimulation or maximal voluntary contraction.20 The study was approved by local ethics committees in the Netherlands and in the UK. After obtaining informed consent, we (MT, PW, PSS, JK or JV) interviewed and examined all patients using a structured checklist, except for 13 whose data were obtained from hospital records and referring neurologists.
Parameters of the derivation sample
Symptoms present within the first three months from onset of disease were used for the purpose of this study, as our goal was to develop a score that is valuable early in the course of disease. Information on the following potential predictors were collected:
- Demographic items, including age at onset, smoking history and weight loss.
The cut-off for age at onset was at 50 years, as SCLC-LEMS is more common than NT-LEMS after then.11 Patients were considered smokers if their lifetime consumption was 100 cigarettes or more.21 Weight loss was dichotomised at loss of 5% of body weight within the first three months, based on former research on SCLC patients.22
- The Karnofsky performance status is an attempt to quantify cancer patients’
general well-being and their quality of life.23 The score runs from 100 to 0, where 100 is ‘perfect’ health and 0 is death. A cut-off value of 70 was chosen as those with lower values need at least occasional assistance for activities of daily living.
- Clinical features included the time of appearance, as described before.12 Disease onset was defined using the first neuromuscular symptom, usually
proximal leg weakness. While autonomic symptoms or fatigue may occur before weakness, these features were often incompletely described and their date of onset proved difficult or impossible to determine.
- For ESR, LDH, leukocyte count and haemoglobin level, we used internationally accepted cut-off values.22
- Immunological parameters: VGCC24 and SOX1 antibodies14, and HLA status.13
Definition of SCLC-LEMS or NT-LEMS
Labelling a case as SCLC-LEMS required histological or cytological proof of SCLC, or for NT-LEMS a follow-up of at least three years after diagnosis of LEMS.
Patients without detectable tumours and follow-up of less than three years were excluded. With current screening strategies, the chances of missing an SCLC after three years are considered remote.12
Validation sample
The score was validated in a cohort of British LEMS patients from Oxford and Nottingham, seen between 1986 and 2009. All patients were seen by the late Professor John Newsom-Davis or by one of the authors (PM or DHJ). Both centres have specific expertise in LEMS. A complete dataset was compiled, as described above.
Statistical analysis
In the derivation sample, univariate logistic regression was used to assess each variable’s predictive value for SCLC. Χ2 analysis was performed, if variables were uniformly present or absent. Factors significantly associated with SCLC in univariate analyses were further included in multivariate analyses.
We performed hierarchical multiple regression based on likelihood ratios. As many variable performed equally well as assessed by their likelihood ratios, the final selection of variables in the score was based on clinical and practical issues.
Where clinical and laboratory data were comparable, preference was given to clinical parameters. If two or more variables were equally associated with presence of SCLC, the factor most easily collected was retained. Imputation of missing values was performed, but since it did not have a significant effect, this was not used. A score was created based on the relative magnitude of the fitted coefficients in the linear predictor of the logistic regression model. This score was compared with a score in which all variables were assigned equal importance. If equally sensitive, preference was given to the unweighted score for sake of
122 LEMS patients
46 SCLC-LEMS 66 NT-LEMS
6 short follow up 3 inadequate screening 1 mixed syndrome 109 LEMS patients
58 SCLC-LEMS 49 NT-LEMS
2 short follow-up
Leiden – derivation set Oxford / Nottingham – validation set Figure 1 Flow chart summarizing all patients from the two cohorts
simplicity. How well the score distinguished between SCLC-LEMS and NT-LEMS was quantified with the area under the curve (AUC) of the receiver operating characteristic (ROC).25 For external validation, the model was applied to the validation dataset. The validation data were not analyzed until the score had been created. Percentages of patients with SCLC, predicted by the prediction model, were calculated using combined datasets to assess reliability. A prior risk of SCLC in LEMS of 50% was used.1, 4-8 Statistical analyses were done with SPSS for Windows 16 (SPSS Inc., Chicago, IL).
Results
The derivation sample included 109 Dutch LEMS patients. Two patients were excluded because follow-up was less than three years. Fifty-eight patients (54%) had an SCLC, and 49 had no tumour (Figure 1). Median follow up of NT-LEMS patients was 7 years (range 3 - 40 years). The following parameters from the patients’ histories differed significantly in univariate analyses: age at onset, weight loss (≥5% within the first 3 months), Karnofsky performance status and smoking related factors (smoking ever, smoking at onset and pack years) (p < 0.001), as well as gender (p = 0.021, Table 1A). The clinical symptoms, that were more frequent in SCLC-LEMS patients within three months, were (Table 1B): weakness in distal leg muscles (p = 0.001), arms (proximal or distal; p < 0.001), bulbar muscles (dysarthria, swallowing, chewing or neck weakness; p < 0.001), male sexual impotence (p = 0.007), dry mouth (p = 0.005) and micturition difficulties (p = 0.019). For laboratory values, raised ESR (p = 0.023), abnormal haemoglobin level (p = 0.018) and leukocyte count (p = 0.004) and presence of SOX1 antibodies (p <
SCLC-LEMS NT-LEMS
< 3 months 58 (54%) 49 (46%) p OR 95% CI
Age at onset (median, range) # 59.7 53.5 < 0.001 1.09 1.04 1.13 (37-77) (15-73)
Age at onset > 50 yr 87.9% 55,1% < 0.001 5.95 2.25 15.63
Gender female 32.8% 55.1% 0.02 2.52 1.15 5.53
Male 67.2% 44.9%
Weight loss > 5% 50.0% 10.4% < 0.001 8.60 2.95 25.04 Karnofsky PS § 70-100 66.1% 100.0% < 0.001 25.79 1.51 441.12
0-60 33.9% 0.0%
Smoking ever § 100.0% 59.2% < 0.001 41.3 2.41 706.99 Smoking at onset 83.9% 30.6% < 0.001 11.84 4.64 30.21 Packyears (median, range) # 38.5 2.5 < 0.001 1.10 1.06 1.13
(10-115) (0-57) Extent of disease limited 64.9%
extended 35.1%
Table 1 A Epidemiological characteristics of the derivation set of 107 LEMS patients.
# Mann Whitney U test; § Χ2 analysis;
SCLC-LEMS NT-LEMS
< 3 months 58 (54%) 49 (46%) p OR 95 % CI
ESR > 30 mm/hr 31.3% 11.1% 0.02 3.64 1.20 11.11
LDH > 450 U/l 15.7% 4.7% 0.10 3.82 0.76 18.87
Haemoglobin < 12 or > 16 g/dl 26.4% 6.8% 0.02 4.90 1.31 18.52 Leucocyte count < 4 or > 10 *109 32.1% 2.3% 0.004 20.41 2.58 166.67 SOX1 antibodies 66.7% 6.3% < 0.001 30.30 8.06 111.11
VGCC antibodies 96.6% 85.4% 0.07 4.52 0.89 22.73
HLA-B8 37.9% 58.3% 0.09 0.44 0.17 1.12
HLA-DR3 24.1% 56.3% 0.008 0.25 0.09 0.69
Table 1 B Laboratory characteristics of the derivation set of 107 LEMS patients.
SCLC-LEMS NT-LEMS
< 3 months 58 (54%) 49 (46%) p OR 95% CI
Proximal legs 96.5% 87.8% 0.11 3.84 0.74 19.97
Distal legs 47.4% 14.3% 0.001 5.40 2.08 14.02
Proximal arms 71.9% 34.7% < 0.001 4.82 2.12 11.00
Distal arms 45.6% 10.2% < 0.001 7.38 2.55 21.34
Eye complaints 41.1% 28.6% 0.18 1.74 0.77 3.95
ptosis 26.3% 20.4% 0.48 1.39 0.56 3.46
diplopia 29.8% 22.4% 0.39 1.47 0.61 3.54
Bulbar complaints 57.1% 18.4% < 0.001 5.93 2.42 14.52
dysarthria 42.9% 16.3% 0.004 3.84 1.53 9.69
dysphagia 35.1% 10.2% 0.004 4.76 1.63 13.91
chewing 32.7% 6.1% 0.002 7.46 2.04 27.28
neck weakness 35.2% 8.2% 0.002 6.11 1.91 19.58
Cerebellar signs 9.1% 2.0% 0.16 4.80 0.54 42.60
Male sexual impotence ‡ 72.4% 31.6% 0.007 5.69 1.61 20.14 male sexual impotence * 43.8% 13.0% 0.002 5.19 1.85 14.53
Dry eyes 16.7% 21.3% 0.58 0.74 0.25 2.16
Dry mouth 71.4% 41.7% 0.005 3.50 1.45 8.45
Micturition difficulties 22.0% 4.2% 0.02 6.49 1.36 31.05
Constipation 16.3% 12.5% 0.59 1.37 0.44 4.28
Orthostatic hypotension 25.0% 10.6% 0.08 2.80 0.89 8.85
Perspiration § 11.1% 0.0% 0.02 7.02 0.38 130.93
Table 1 C Clinical characteristics of the derivation set of 107 LEMS patients.
§ Χ2 analysis; ‡ 61 males; * analysis with women included, scored as ‘normal’
0.001) differed significantly between NT-LEMS and SCLC-LEMS (Table 1C). HLA- DR3 was the only factor seen more frequently in NT-LEMS (p = 0.008).
Formation of the score in the derivation sample
In the derivation set, 4% of data were missing. All data were available for 100 patients (52 SCLC-LEMS) for multivariate analysis. Age at onset, smoking at onset, weight loss, bulbar symptoms and male sexual impotence (within three months)
and SOX1 antibodies proved the main predictors of SCLC in LEMS patients (Table 2). As Karnofsky performance status under 70 was unequivocally associated with SCLC, we also added it to our score.
The AUC using all factors was 96.6%. Omitting weighting of factors had a negligible effect (AUC 96.2%). Weighting, that reduces the easy applicability of the score, was therefore not used. To investigate the accuracy of a score restricted to clinical and epidemiological parameters, the AUC was calculated without SOX1 antibodies. The resulting AUC of this six-point score was slightly lower at 94.4%
(Figure S1 A), but since this approach did not alter appreciably the proportions of patients with low-risk or high-risk scores, this purely clinical score was chosen to be used in the validation sample (Table 3).
Evaluation of the score in the validation sample
The validation sample consisted of 122 British patients of which 112 patients were included, 13 from Nottingham and 99 from Oxford (Figure 1). Ten patients had to be excluded because they had short follow-up (6) or had no or incomplete tumour screening (3). One patient was excluded because of co-existence of myasthenia gravis, since precise onset of clinical features could not be determined. Of these 112 patients, 46 had an SCLC (41%, p ~ 0.05 versus the Leiden cohort).
Derivation set Validation set Combined sets
(n = 100) p (n = 100) p (n = 200) p
Smoking at onset 11.6 (2.5-53.0) 0.002 36.7 (5.3-253) < 0.001 13.6 (4.4-42.1) < 0.001 Age at onset
(> 50yrs) 9.5 (1.5-62.6) 0.02 20.1 (2.1-191) 0.009 14.7 (3.6-61.3) < 0.001 Weight loss (> 5%) 11.4 (2.2-59.6) 0.004 7.3 (1.1-48.4) 0.04 6.9 (2.2-21.8) 0.001 Bulbar symptoms 7.4 (1.7-31.7) 0.007 4.6 (0.8-27.3) 0.09 6.8 (2.3-19.7) < 0.001 Male sexual
impotence * 7.1 (1.5-33.5) 0.01 0.43 (0.05-3.9) 0.45 3.3 (1.1-10.7) 0.04 Karnofsky PS (< 70) # # 46.9 (2.4-930) 0.01 24.3 (2.5-233) 0.006 SOX1 antibodies 7.8 (1.3-45.4) 0.02 32.1 (2.0-506) 0.01 11.5 (2.7-48.2) 0.001
Table 2 Multivariate odds ratios (95% CI) from logistic regression models for the prediction of SCLC. # not applicable, as 0% abnormal in NT-LEMS; * analysis with women included, scored as ‘normal’
Univariate analyses of the UK cohort and both cohorts combined can be found in the supplementary material (Tables S1 and S2 A-C). The two cohorts were very similar. Some variables seemed different. SOX1 antibodies were found in 45% of British SCLC-LEMS patients versus 66.7% in the Dutch (p ~ 0.26) and male sexual impotence in 52.9% in the UK versus 72.4% in the Netherlands (p ~ 0.18).
All data were available for 100 British LEMS patients, 35 with SCLC.
Multivariate odds ratios proved comparable to those in the derivation set (Table 2).
The discriminatory abilities of the score in the second cohort were very good as well, with an AUC of 94.6% (Figure S1 B).
We created the Dutch-English LEMS Tumour Association Prediction (DELTA-P) score, combining both cohorts (n = 200). Each item is scored equally, creating a score ranging from 0 to 6, directly correlating with increasing risk of
Categories Score
D Dysarthria, dysphagia, chewing, neck weakness absent 0
(bulbar weakness) present 1
E Erectile dysfunction female 0
male: absent 0
male: present 1
L Loss of Weight absent or < 5% 0
≥ 5 % 1
T Tobacco use at onset absent 0
present 1
A Age of onset < 50 years 0
- ≥ 50 years 1
P Karnofsky Performance Score 70-100 0
0-60 1
DELTA-P score 0 - 6
Table 3 The Dutch-English LEMS Tumour Association Prediction score
SCLC (Table 3), as shown in Figure 2 (data supplementary, Table S3). A score of 0 or 1 virtually excludes an SCLC with a risk of 0% or 2.6%. A score of 3 to 6 should alert the physician to screen vigorously, as the risk for SCLC rises from 83.9% to 93.5%, 96.6% and even 100%, respectively. To illustrate the use of our score, two LEMS patients are discussed (box).
Case 1 is a 62 year old male patient, who was still smoking (40 pack years). His Karnofsky performance status was 60 and he lost 8 kilograms (10%) within the first three months. He had a subacute onset of weakness in legs and arms, with rapid spreading to the feet and hands, though not to the bulbar region. He had autonomic symptoms from the start (impotence, micturition difficulties and constipation). His DELTA-P score was 5, corresponding to an SCLC risk of 96%.
He was screened by X-thorax, CT-thorax, lumbar puncture and FDG-PET scan, which were all reported to be normal. Three months later, MRI of the thoracolumbar region, performed because of pain, showed a lesion which histologically proved to be an SCLC metastasis. Retrospectively, the spot was already visible on FDG-PET. He was treated with chemotherapy and radiotherapy, resulting in temporary remission. Twenty-eight months after onset, he developed a cerebellar metastasis. A primary lung tumour was never found. He was treated by resection and adjuvant whole brain radiotherapy. He died 52 months after onset of symptoms due to his cerebral metastases. If the DELTA-P score and implied 96.6% risk of SCLC had been known, the initial screening would probably have been more rigorous.
Case 2. A 68 year old woman stopped smoking 8 years before the onset of symptoms (10 pack years). Karnofsky performance status was 90 and she had no weight loss. She presented with difficulties climbing stairs, dry eyes and dry mouth and did not develop bulbar symptoms for 7 months. She had a DELTA-P score of 1, corresponding to a predicted risk of SCLC of 2.6%. She died at the age of 92, without any sign of SCLC over 24 years of follow up.
Two illustrative cases
Figure 2 Predicted fraction of SCLC in LEMS patients based on the Dutch-English LEMS Tumour Association Prediction score. Point sizes proportionate to the number of patients with a specific score, also represented by the percentage inside the circle. Vertical bars indicate standard error of the mean.
Discussion
Prognosis and treatment of LEMS differs greatly depending on whether the patient has an SCLC or not. We have developed and validated a simple clinical scoring system, the DELTA-P score, that can be easily applied in the clinic to predict with
>94% reliability the likelihood of SCLC in patients with LEMS early in the course of their neurological disease. Based on age at onset, smoking at onset, weight loss, Karnofsky performance status, bulbar symptoms and male sexual impotence, all within three months from onset, our score indicates the presence of SCLC with very high accuracy. This score provides physicians with a tool to identify high-risk patients, to reassure patients with very low risk, and to guide the screening process and follow-up.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5 6
Probability of SCLC (%)
DELTA-P score 22
14
13 2
15
22 13
Choice of variables for our DELTA-P score
In previous studies, many factors were associated with SCLC in LEMS patients.
Univariate analyses corroborated their associations with SCLC, all confirming our clinical impression that SCLC-LEMS patients are more severely disabled more early in the course of disease than those without SCLC. Age at onset, smoking and early involvement of clinical features (bulbar weakness, weakness in distal legs, proximal and distal arms and male sexual impotence) had already been identified as predictors for SCLC.1, 10, 12 Some patients in these studies were included in our derivation10, 12 and validation sets.1 ESR, HLA-B8 and HLA-DR3 differed significantly in univariate analyses,1, 10, 17
but had no independent discriminatory value in multivariate analyses. The HLA-B8 and HLA-DR3 association is only evident in NT-LEMS presenting before 50 years (own data, not published), which explains why HLA does not add to our score. SOX1 antibodies14, 15 remained an independent predictor in multivariate analysis, as the AUC was 1.8% higher when they were included. However, SOX1 antibody tests are not commercially available yet and rather time-consuming. Besides, their inclusion in the score did not affect the percentage of patients with scores of either 0 or 1 (very low risk) or 4, 5 or 6 (very high risk). Differences were found for patients with a score of 3 (22% of patients), subdividing the group in two high-risk groups, which would have no impact on screening strategy. Therefore, we decided to omit SOX1 antibodies.
The use of easy-to-obtain directly available clinical characteristics, avoidance of weighting of factors and the use of a double acronym (Table 3) will enhance the practical implementation of the DELTA-P score.
Comparison of the two cohorts
The Dutch and British cohorts were comparable for SCLC-LEMS as well as for NT- LEMS, with a few exceptions. British NT-LEMS patients smoked less at onset, most likely because of the earlier decline in smoking habits in the UK than in the Netherlands, from 36.2% in the Netherlands versus 28% in the UK in 1992, and 29.1% versus 21% in 2007.26, 27 Male sexual impotence was reported more often in the Netherlands than in the UK. Patients in the derivation sample were interviewed with a structured questionnaire, which might explain the higher frequency and less missing data of impotence and other signs of autonomic dysfunction. The prevalence of SOX1 antibodies was lower in the British cohort especially for sera drawn over 5 years ago, concerning patients who had been treated with chemotherapy or immunosuppressants. Sera from British patients with SCLC-
LEMS, drawn within the last five years, were positive in 67%, comparable to published percentages.14, 15
Overall, more data were missing in the SCLC-LEMS group because some patients had died before additional information could be gathered. However, these comprise a small fraction of our study group and as these were especially the more severely disabled patients, any resulting bias would almost certainly have led us to underestimate the potential of our score.
SCLC-LEMS to NT-LEMS ratio
The association between LEMS and SCLC is clear, but reported percentages of SCLC-LEMS range from 40% to 70%. Such differences probably reflect patient ascertainment, whether by cross-sectional or prospective collection of patients, and selection bias. Neuromuscular centres see more NT-LEMS patients, while neuro- oncology departments see more SCLC-LEMS patients. In our cohorts, SCLC- LEMS was found in 54% and 41% in the derivation and validation sets respectively.
Whereas the Dutch cohort was collected nationwide, via both neuromuscular and neuro-oncology centres, nearly all the UK patients were referred to the neuromuscular clinic in Oxford, explaining the lower percentages of SCLC-LEMS.
Overall, 50% to 60% seems to be reasonable. For this, we used a prior chance of 50% for calculating the consequences of our DELTA-P score (Figure 2). This assumption hardly affects applicability of the score, as different prior chances (40- 70%) only affected patients with a DELTA-P score of 2 (Figure S2), who must be re-screened anyway and comprise only 15% of patients (Figure 2).
Other tumours than SCLC in LEMS
Though other tumours have been associated with LEMS,28 it is hard to distinguish between chance and cause. Among 113 NT-LEMS patients included, only four tumours were found in three patients without any effect on their neuromuscular symptoms. One patient had breast cancer six years before onset of LEMS, followed by non-Hodgkin lymphoma (NHL) twenty years after the diagnosis of LEMS. Endometrial carcinoma and NHL were found in a second and third patient 7 and 12 years after onset of LEMS. Both NHL were found in patients who had been treated with high doses of immunosuppressants. According to recommendations of the Paraneoplastic Neurological Syndromes Euronetwork29 these patients were regarded as NT-LEMS patients. Their DELTA-P scores were 3, 0 and 1.
Recommendations for screening
In 2008, we proposed a screening strategy based on data from our derivation set.9 Each patient should be screened by CT-thorax and FDG-PET (or integrated FDG- PET/CT). If negative, this should be repeated after 6 months by CT-thorax or FDG- PET, to be repeated every 6 months for two years. As overlooking a SCLC is not acceptable, we propose to screen every patient at least twice. The DELTA-P score can help to guide the need for further screening. In patients with a DELTA-P score of 0 or 1, we suggest to stop screening after two adequate and negative screens.
The chance of developing a SCLC afterwards is less than 1 per 1000, even if calculated conservatively. If the score is 3-6, the second screening should be performed earlier, after three months, and should be repeated every 6 months afterwards for two years. In fact, the physician should be continuously vigilant for signs pointing towards SCLC. In patients with a DELTA-score of 2, screening should remain as proposed before, every 6 months for two years.9
In conclusion, SCLC can be predicted accurately in LEMS patients, which will help to provide better clinical care to all patients. The DELTA-P score can be used in routine clinical practice to prioritise high-risk patients for intensive tumour screening, while it will also identify those with very low tumour risk, who can be reassured in an early phase of the screening process.
References
1. O'Neill JH, Murray NMF, Newsom-Davis J. The Lambert-Eaton Myasthenic Syndrome - A Review of 50 Cases. Brain 111:577-596, 1988
2. Roberts A, Perera S, Lang B, Vincent A, Newsom-Davis J. Para-Neoplastic Myasthenic Syndrome IgG Inhibits Ca-45(2+) Flux in A Human Small Cell- Carcinoma Line. Nature 317(6039):737-739, 1985
3. Lambert EH, Eaton LM, Rooke ED. Defect of Neuromuscular Conduction Associated with Malignant Neoplasms. American Journal of Physiology 187(3):612-613, 1956
4. Elmqvist D, Lambert EH. Detailed Analysis of Neuromuscular Transmission in A Patient with Myasthenic Syndrome Sometimes Associated with Bronchogenic Carcinoma. Mayo Clin Proc 43(10):689-713, 1968
5. Gutmann L, Phillips LH, Gutmann L. Trends in the association of Lambert- Eaton myasthenic syndrome with carcinoma. Neurology 42(4):848-850, 1992 6. Nakao YK, Motomura M, Fukudome T et al. Seronegative Lambert-Eaton
myasthenic syndrome. Neurology 59(11):1773-1775, 2002
7. Tim RW, Massey JM, Sanders DB. Lambert-Eaton myasthenic syndrome:
Electrodiagnostic finding and response to treatment. Neurology 54(11):2176- 2178, 2000
8. Wirtz PW, van Dijk JG, van Doorn PA et al. The epidemiology of the Lambert-Eaton myasthenic syndrome in the Netherlands. Neurology 63(2):397-398, 2004
9. Titulaer MJ, Wirtz PW, Willems LN, van Kralingen KW, Smitt PA, Verschuuren JJ. Screening for small-cell lung cancer: a follow-up study of patients with lambert-eaton myasthenic syndrome. J Clin Oncol 26(26):4276- 4281, 2008
10. Wirtz PW, Willcox N, van der Slik AR et al. HLA and smoking in prediction and prognosis of small cell lung cancer in autoimmune Lambert-Eaton myasthenic syndrome. J Neuroimmunol 159(1-2):230-237, 2005
11. Titulaer MJ, Verschuuren JJ. Lambert-Eaton Myasthenic Syndrome: Tumor versus Nontumor Forms. Ann N Y Acad Sci 1132:129-134, 2008
12. Titulaer MJ, Wirtz PW, Kuks JB et al. The Lambert-Eaton myasthenic syndrome 1988-2008: A clinical picture in 97 patients. J Neuroimmunol 201- 202:153-158, 2008
13. Wirtz PW, Wintzen AR, Verschuuren JJ. Lambert-Eaton myasthenic syndrome has a more progressive course in patients with lung cancer.
Muscle Nerve 32(2):226-229, 2005
14. Sabater L, Titulaer M, Saiz A, Verschuuren J, Gure AO, Graus F. SOX1 antibodies are markers of paraneoplastic Lambert-Eaton myasthenic syndrome. Neurology 70(12):924-928, 2008
15. Titulaer MJ, Klooster R, Potman M et al. SOX antibodies in small-cell lung cancer and Lambert-Eaton myasthenic syndrome: frequency and relation with survival. J Clin Oncol 27(26):4260-4267, 2009
16. Parsons KT, Kwok WW, Gaur LK, Nepom GT. Increased frequency of HLA class II alleles DRB1*0301 and DQB1*0201 in Lambert-Eaton myasthenic
syndrome without associated cancer. Human Immunology 61(8):828-833, 2000
17. Willcox N, Demaine AG, Newsomdavis J, Welsh KI, Robb SA, Spiro SG.
Increased Frequency of Igg Heavy-Chain Marker Glm(2) and of Hla-B8 in Lambert-Eaton Myasthenic Syndrome with and Without Associated Lung- Carcinoma. Human Immunology 14(1):29-36, 1985
18. Wirtz PW, Roep BO, Schreuder GMT et al. HLA class I and II in Lambert- Eaton myasthenic syndrome without associated tumor. Human Immunology 62(8):809-813, 2001
19. Sanders DB. Lambert-Eaton myasthenic syndrome: clinical diagnosis, immune-mediated mechanisms, and update on therapies. Ann Neurol 37 Suppl 1:S63-S73, 1995
20. Practice parameter for repetitive nerve stimulation and single fiber EMG evaluation of adults with suspected myasthenia gravis or Lambert-Eaton myasthenic syndrome: summary statement. Muscle Nerve 24(9):1236-1238, 2001
21. Muscat JE, Wynder EL. Lung cancer pathology in smokers, ex-smokers and never smokers. Cancer Lett 88(1):1-5, 1995
22. Paesmans M, Sculier JP, Lecomte J et al. Prognostic factors for patients with small cell lung carcinoma - Analysis of a series of 763 patients included in 4 consecutive prospective trials with a minimum follow-up of 5 years.
Cancer 89(3):523-533, 2000
23. Karnofsky DA, Burchenal JH. The Clinical Evaluation of Chemotherapeutic Agents in Cancer. In: MacLeod CM, editor. Evaluation of Chemotherapeutic Agents. Columbia Univ Press; 1949
24. Motomura M, Lang B, Johnston I, Palace J, Vincent A, Newsomdavis J.
Incidence of serum anti-P/Q-type and anti-N-type calcium channel autoantibodies in the Lambert-Eaton myasthenic syndrome. J Neurol Sci 147(1):35-42, 1997
25. Altman DG, Bland JM. Diagnostic tests 3: receiver operating characteristic plots. BMJ 309(6948):188, 1994
26. Statistics Netherlands. http://statline.cbs.nl/statweb, 2007
27. WHO/Europe, European HFA Database. World Health Organization Regional Office for Europe Health For All Database.
http://data.euro.who.int/hfadb, 2010
28. Wirtz PW, Smallegange TM, Wintzen AR, Verschuuren JJ. Differences in clinical features between the Lambert-Eaton myasthenic syndrome with and without cancer: an analysis of 227 published cases. Clinical Neurology and Neurosurgery 104(4):359-363, 2002
29. Graus F, Delattre JY, Antoine JC et al. Recommended diagnostic criteria for paraneoplastic neurological syndromes. J Neurol Neurosurg Psychiatry 75(8):1135-1140, 2004
Supplementary tables and figures
SCLC-LEMS NT-LEMS
< 3 months 46 (41%) 66 (59%) p OR 95% CI
Age at onset (median, range) # 70.0 51.9 < 0.001 1.10 1.05 1.15 (34-77) (11-74)
Age at onset > 50 yr 88.9% 56.1% < 0.001 6.41 2.25 18.18
Gender female 37.0% 50.0% 0.17 1.71 0.79 3.68
male 63.0% 50.0%
Weight loss > 5% 59.5% 7.7% < 0.001 17.60 5.72 54.15 Karnofsky PS § 70-100 62.5% 96.9% < 0.001 18.90 4.03 88.73
0-60 37.5% 3.1%
Smoking ever § 100.0% 46.2% < 0.001 52.26 3.09 884.72 Smoking at onset 82.2% 18.5% < 0.001 20.43 7.60 54.88 Packyears (median, range) # 50 0 < 0.001 1.11 1.07 1.15
(7-184) (0-59)
Table S1 A Epidemiological characteristics of the derivation set of 112 LEMS patients.
# Mann Whitney U test; § Χ2 analysis;
SCLC-LEMS NT-LEMS
< 3 months 46 (41%) 66 (59%) p OR 95 % CI
ESR > 30 mm/hr 14.3% 4.3% 0.17 3.66 0.56 23.81
Haemoglobin < 12 or > 16 g/dl 0.0% 7.7% 0.15 0.36 0.02 7.00 Leucocyte count < 4 or > 10 *109 15.4% 3.8% 0.09 4.55 0.77 27.03 SOX1 antibodies 45.0% 4.1% < 0.001 19.23 4.10 90.91
VGCC antibodies 90.9% 85.0% 0.42 1.76 0.44 7.04
HLA-B8 13.6% 57.1% 0.003 0.12 0.03 0.49
HLA-DR3 19.0% 67.9% 0.001 0.11 0.03 0.43
Table S1 B Laboratory characteristics of the derivation set of 112 LEMS patients.
SCLC-LEMS NT-LEMS
< 3 months 46 (41%) 66 (59%) p OR 95% CI
Proximal legs § 100.0% 92.4% 0.06 4.45 0.24 82.57
Distal legs 42.5% 7.6% < 0.001 9.02 2.98 27.27
Proximal arms 90.5% 30.3% < 0.001 21.85 6.88 69.44
Distal arms 48.8% 6.1% < 0.001 14.76 4.53 48.14
Eye complaints 43.9% 16.7% 0.003 3.91 1.60 9.57
ptosis 31.0% 10.6% 0.01 3.78 1.36 10.49
diplopia 26.8% 10.6% 0.03 3.09 1.09 8.78
Bulbar complaints 52.4% 13.6% < 0.001 6.97 2.76 17.62
dysarthria 40.5% 9.1% < 0.001 6.80 2.40 19.26
dysphagia 22.5% 3.0% 0.006 9.29 1.89 45.61
chewing 12.5% 1.5% 0.05 9.29 1.04 82.64
neck weakness 31.7% 7.6% 0.003 5.66 1.84 17.43
Cerebellar signs 16.3% 3.0% 0.03 6.22 1.23 31.56
Male sexual impotence ‡ 52.9% 32.1% 0.17 2.38 0.69 8.20 male sexual impotence * 26.5% 14.8% 0.17 2.08 0.74 5.88
Dry eyes § 0.0% 0.0% 1.00
Dry mouth 87.8% 38.1% < 0.001 11.70 4.04 33.93
Micturition difficulties 16.1% 8.1% 0.25 2.19 0.58 8.24
Constipation 42.2% 14.3% 0.003 4.42 1.65 11.87
Orthostatic hypotension 34.8% 6.1% 0.004 8.18 1.92 34.84
Perspiration § 0.0% 5.3% 0.30 0.59 0.03 12.83
Table S1 C Clinical characteristics of the derivation set of 112 LEMS patients.
§ Χ2 analysis; ‡ 62 males; * analysis with women included, scored as ‘normal’
SCLC-LEMS NT-LEMS
< 3 months 104 (47%) 115 (53%) p OR 95% CI
Age at onset (median, range) # 60.2 52.1 < 0.001 1.09 1.06 1.12 (34-77) (11-74)
Age at onset > 50 yr 88.5% 55.7% < 0.001 6.10 3.02 12.35
Gender female 34.6% 52.2% 0.009 2.06 1.20 3.55
male 65.4% 47.8%
Weight loss > 5% 53.8% 8.8% < 0.001 12.02 5.57 25.93 Karnofsky PS 70-100 64.6% 98.2% < 0.001 30.44 7.07 131.00
0-60 35.4% 1.8%
Smoking ever 100.0% 51.8% < 0.001 96.13 5.83 1584.97 Smoking at onset 83.2% 23.7% < 0.001 15.92 8.09 31.33 Packyears (median, range) # 40 1 < 0.001 1.10 1.08 1.13
(7-184) (0-59)
Table S2 A Epidemiological characteristics of the combined sets of 219 LEMS patients.
# Mann Whitney U test; § Χ2 analysis;
SCLC-LEMS NT-LEMS
< 3 months 104 (47%) 115 (53%) p OR 95% CI
ESR > 30 mm/hr 26.1% 7.7% 0.003 4.24 1.66 10.87
LDH > 450 U/l 20.7% 4.4% 0.03 5.62 1.19 26.32
Haemoglobin < 12 or > 16 g/dl 17.7% 7.3% 0.04 2.74 1.05 7.14 Leucocyte count < 4 or > 10 *109 26.6% 3.1% < 0.001 11.24 3.21 40.00
SOX1 antibodies 56.8% 5.2% < 0.001 24.39 8.93 66.67
VGCC antibodies 94.3% 86.0% 0.06 2.71 0.94 7.75
HLA-B8 27.5% 57.9% 0.001 0.28 0.13 0.59
HLA-DR3 22.0% 60.5% < 0.001 0.18 0.08 0.41
Table S2 B Laboratory characteristics of the combined sets of 219 LEMS patients.
SCLC-LEMS NT-LEMS
< 3 months 104 (47%) 115 (53%) p OR 95% CI
Proximal legs 98.0% 91.2% 0.03 5.29 1.14 24.46
Distal legs 45.4% 10.4% < 0.001 7.13 3.47 14.63
Proximal arms 79.8% 32.2% < 0.001 8.33 4.45 15.60
Distal arms 46.9% 7.8% < 0.001 10.42 4.74 22.90
Eye complaints 42.3% 21.7% 0.002 2.64 1.45 4.80
ptosis 28.3% 14.8% 0.02 2.27 1.16 4.47
diplopia 28.6% 15.7% 0.02 2.16 1.11 4.20
Bulbar complaints 55.1% 15.7% < 0.001 6.61 3.48 12.56 dysarthria 41.8% 12.2% < 0.001 5.19 2.61 10.33
dysphagia 29.9% 6.1% < 0.001 6.58 2.73 15.85
chewing 24.2% 3.5% < 0.001 8.87 2.94 26.70
neck weakness 33.7% 7.8% < 0.001 5.98 2.68 13.35
Cerebellar signs 12.2% 2.6% 0.01 5.21 1.43 19.04
Male sexual impotence ‡ 65.2% 31.9% 0.002 4.00 1.69 9.48 male sexual impotence * 36.6% 14.0% < 0.001 3.54 1.75 7.18
Dry eyes 11.3% 9.5% 0.72 1.21 0.44 3.36
Dry mouth 79.5% 39.6% < 0.001 5.91 3.07 11.38
Micturition difficulties 19.8% 6.4% 0.007 3.62 1.41 9.28
Constipation 26.8% 13.5% 0.02 2.35 1.13 4.88
Orthostatic hypotension 28.4% 8.3% 0.001 4.35 1.77 10.69
Perspiration 7.7% 2.4% 0.15 3.46 0.65 18.43
Table S2 C Clinical characteristics of the combined sets of 219 LEMS patients.
§ Χ2 analysis; ‡ 123 males; * analysis with women included, scored as ‘normal’
Derivation set Validation set Combination Share of total LR +
n = 107 n = 112 n = 219 (%)
0 0/11 0.0% 0/18 0.0% 0/29 0.0% 14.5% 0.00
1 0/21 0.0% 1/29 3.4% 1/50 2.0% 25.0% 0.03
2 5/14 35.7% 2/17 11.8% 7/31 22.6% 15.5% 0.38
3 17/24 70.8% 15/16 93.8% 32/40 80.0% 20.0% 5.20
4 15/15 100.0% 7/9 77.8% 22/24 91.7% 12.0% 14.29
5 14/14 100.0% 8/9 88.9% 22/23 95.7% 11.5% 28.57
6 1/1 100.0% 2/2 100.0% 3/3 100.0% 1.5% ∞
Total 52/100 52.0% 35/100 35.0% 87/200 43.5% 100.0%
Table S3 Number of LEMS patients with SCLC in the derivation and validation sets according to the Dutch-English LEMS Tumour Association Prediction score.
Figure S1 Receiver operator characteristic (ROC) to calculate the area under the curve (AUC) for the DELTA-P score for the derivation set (left) and the validation set (right).
Figure S2 Predicted fractions of SCLC in LEMS patients, depending on different prior chances, based on the Dutch-English LEMS Tumour Association Prediction score.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5 6
Probability of SCLC (%)
DELTA-P score
0,4 0,5 0,6 0,7
