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We read with interest the report by Janssen-Heijnen and associates on the effect of comorbidity on the treatment and prognosis of elderly patients with non-small cell lung cancer (NSCLC).1 The authors concluded that the number of comorbid conditions had no significant influence on the treatment chosen for patients with non-localised disease. We share the authors’ opinion that “comorbidity had no independent prognostic effect”.
In their report, the authors used the Charlson comorbidity index and analysed the number of comorbid conditions.1 However, they did not examine the scoring system of the index. We would like to know why the authors did not use the scoring of the index, and whether the conclusion would be changed if the scoring system was used.
In the original article by Charlson et al and other related studies,2–5 “angina pectoris” was not evaluated as one of the cardiovascular comorbid diseases. However, Janssen-Heijnen et al1 included “angina pectoris” as a comorbid disease although they did not describe it precisely. We consider this inclusion is reasonable, and we would appreciate hearing from the authors whether “angina pectoris” would be evaluated as one of the cardiovascular comorbid diseases in future studies to evaluate the effect on mortality, and what score it should be assigned.
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Authors’ reply
Miyazaki and colleagues wonder why we did not use the scoring system of Charlson’s comorbidity index and whether the conclusion would be different if the scoring system was used. We did not use the scoring system of Charlson’s index because this was not available in the large population based database from which the data were derived. We were, however, able to analyse the prognostic impact of each condition and each combination of conditions. None of these had a significant prognostic impact.1 The conclusion might have been different if we had used the scoring system. However, in two other recent studies2,3 the hazard ratio for death for comorbidity was much lower for patients with a lethal tumour than for those with a tumour with a good prognosis.
We also included angina pectoris as a comorbid condition. We think it is important to include this condition in future studies. In other studies hospitalisation for angina or treated angina was classified as high severity for mortality, and angina not requiring hospitalisation or untreated angina was classified as moderate severity.2,4–6 The severity index should be validated in future studies.