Table 3. Multiple Stepwise Linear Regression Analysis of Overall Survival (Per Treatment Arm).

Factor	Regression Coefficient*	SE	P †
Year of trial initiation	Excluded
Use of PE regimen (y or n)	Excluded
Proportion of patients with good PS	6.65	1.30	<0.001
Proportion of male patients	Excluded
Median age of patients	Excluded
Design of the PCI setting (y or n)	2.14	0.742	0.009
Description of definition for ED (y or n)	Excluded

*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.