Improved Overall Survival Trends of Men with Newly Diagnosed M1 Prostate Cancer: A SWOG Phase III Trial Experience (S8494, S8894 and S9346)

Abstract

Frequent prostate specific antigen testing for screening and monitoring prostate cancer has led to significant stage migration. We evaluated whether overall survival in hormone naïve patients with metastatic prostate cancer has improved during the era of prostate specific antigen use. We also assessed whether any patient subsets benefited differentially during this period. We compared overall survival in 3 sequential phase III trials of 3,096 men with hormone naïve, metastatic prostate cancer who received similar androgen deprivation therapy, including 2 trials performed before the prostate specific antigen era (S8494 and S8894) and the other done during this era (S9346). Overall survival was adjusted for patient and disease risk factors in the latter 2 trials. Subgroups were evaluated by interactions of risk factors with trial. Median overall survival was 30 months in S8494, 33 months in S8894 and 49 months in S9346. Adjusting for risk factors, there was a 22% lower risk of death in S9346 than in S8894 (HR 0.78, 95% CI 0.70, 0.87, p <0.001). The improvement in overall survival was greater in black American men (test of interaction p = 0.008). In S8494 and S8894 median survival for black men was 27 months, and 34 and 35 months for nonblack men, respectively. This racial difference disappeared in S9346 with overall survival of 48 and 49 months in black and nonblack men, respectively. Adjusting for risk factors, overall survival was significantly improved in the post-prostate specific antigen era trial. However, it cannot be concluded that this was attributable only to prostate specific antigen monitoring. Black men now have overall survival comparable to that of white men. Current estimates of survival should be used to design new trials in this population.