Letters to the Editor

Abstract

I have read with great interest the article “Prognostic Factors for Survival in Extensive Stage Small Cell Lung Cancer” by Ou et al.1Ou SH Ziogas A Zell JA Prognostic factors for survival in extensive stage small cell lung cancer (ED-SCLC): the importance of smoking history, socioeconomic and marital statuses, and ethnicity.J Thorac Oncol. 2009; 4: 37-43Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar However, I have a few questions for the authors. The study covers a 15-year period (1991-2005) and the authors report a median follow-up of 12 months for limited disease stage and of 5 months for extensive disease (ED) stage. The date of point should have been provided, but this duration of follow-up is surprising. This would mean that if the date of point was December 31, 2005 half of the patients with limited disease stage were diagnosed after December 31, 2004 and half of the patients with ED after July 2005 … which seems quite impossible. Is not there a mistake regarding the definition of follow-up? One may expect that there was a period effect, for example, for administration of chemotherapy and radiotherapy. The relatively low rate of treatment with chemotherapy (68.8%) in this highly chemosensitive tumor is striking especially regarding the fact that this is a global percentage without taking into account that the percentage was probably even lower during the first years. As a matter of fact, in a population-based study performed in the Bas-Rhin (a North Eastern department of France) and covering 16 years, 68.2% of the patients with ED were treated with chemotherapy during years 1981-1983, but there was a progressive increase in this percentage with time and 93% received chemotherapy in the years 1993-1994.2Lebitasy MP Hedelin G Purohit A Moreau L Klinzig F Quoix E Progress in the management and outcome of small-cell lung cancer in a French region from 1981 to 1994.Br J Cancer. 2001; 85: 808-815Crossref PubMed Scopus (40) Google Scholar In another population-based study performed in the Netherlands from 1975 to 1994, the percentage of patients with ED receiving chemotherapy (with or without radiotherapy) during the 1990-1994 period was 81% for the 128 patients aged less than 70 years and 53% for the 68 patients aged more than 70 years, which represent a global percentage of 72%. The period effect should also be taken into account for survival analysis, because there is probably an improvement over time of the survival as in the above cited articles1Ou SH Ziogas A Zell JA Prognostic factors for survival in extensive stage small cell lung cancer (ED-SCLC): the importance of smoking history, socioeconomic and marital statuses, and ethnicity.J Thorac Oncol. 2009; 4: 37-43Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar, 2Lebitasy MP Hedelin G Purohit A Moreau L Klinzig F Quoix E Progress in the management and outcome of small-cell lung cancer in a French region from 1981 to 1994.Br J Cancer. 2001; 85: 808-815Crossref PubMed Scopus (40) Google Scholar or in the SEER database with a 2-month improvement of median survival time from 1972 to 19943Chute JP Chen T Feigal E Simon R Johnson BE Twenty years of phase III trials for patients with extensive-stage small-cell lung cancer: perceptible progress.J Clin Oncol. 1999; 17: 1794-1801PubMed Google Scholar and also an increase of survival of the general population, which is better analyzed using relative survival rather than crude survival. Smoking history does not seem as a prognostic factor in univariate analysis of survival with a 1-year, 2-year, and median overall survival time of 20.9%, 5.5%, and 6 months, respectively, in smokers and 21.9%, 6.9%, and 6 months, respectively, in neversmokers (p = 0.7455). However, it does seem as a significant independent prognostic factor in multivariate analysis. This is quite inexplicable regarding the very similar rates of survival in univariate analysis. Usually, only variables that are significant in univariate analysis of survival or at least with a p value less than 0.3 are included in the multivariate analysis. Here, the p value was 0.7455. I would be happy to read the answers of the authors to these comments.