Multiple Stepwise Linear Regression Analysis of Overall Survival (Per Treatment Arm).

*Threshold F values for entering and removing from the model were 0.05 and 0.10, respectively. †P<0.05 was considered significant. This multivariate stepwise regression model excluded the factors “Year of trial initiation,” “Use of PE regimen,” “Proportion of male patients,” “Median age of patients,” and “Description of definition for ED” from the model. Abbreviations: PE, cisplatin and etoposide; PS, performance status; PCI, prophilactic cranial irradiation; ED, extended disease.