Yamaguchi Takuhiro, Ohashi Yasuo
Department of Biostatistics/Epidemiology and Preventive Health Sciences, School of Health Sciences and Nursing, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, 113-0033, Japan.
Stat Med. 2004 Jul 15;23(13):2005-22. doi: 10.1002/sim.1817.
The CPT-11 trial was conducted to confirm the superiority of CDDP+CPT-11 (CPT-P) arm to CDDP+VDS (VDS-P) arm with regard to survival for patients with previously untreated advanced (stage IIIB/IV) non-small-cell lung cancer. However, the CPT-P arm did not show the survival benefit for patients with stage IIIB. The proportion of patients with stage IIIB treated by active radiation given as second-line treatment (second-line radiotherapy) after initial (first-line) treatment was 45 per cent in the CPT-P arm while 61 per cent in the VDS-P arm. This showed that not proving survival advantage in the CPT-P arm might be due to the benefits of second-line radiotherapy. We apply two causal models appeared in the companion paper to test and estimate the survival differences that would have been observed if all the patients had been received the same second-line radiotherapy. Based on several assumptions, we inferred that the CPT-P arm still would not have showed survival advantage if all the patients had been given identical second-line radiotherapy.
CPT-11试验旨在证实，对于先前未经治疗的晚期（IIIB/IV期）非小细胞肺癌患者，顺铂+CPT-11（CPT-P）组在生存率方面优于顺铂+长春地辛（VDS-P）组。然而，CPT-P组并未显示出对IIIB期患者的生存获益。在初始（一线）治疗后接受二线治疗（二线放疗）的IIIB期患者比例，CPT-P组为45%，而VDS-P组为61%。这表明，CPT-P组未证明生存优势可能归因于二线放疗的益处。我们应用配套论文中出现的两种因果模型，来检验和估计如果所有患者都接受相同的二线放疗时可能观察到的生存差异。基于若干假设，我们推断，如果所有患者都接受相同的二线放疗，CPT-P组仍不会显示出生存优势。
