Biopsy specimens were obtained from 120 of 875 men in the Scandinavian Prostate Cancer Group-7 study.
Biopsies were performed at median of 45 months follow-up. In 63 patients receiving endocrine treatment only and 57 patients receiving combined treatment, residual cancer was found in 66 % (n = 41) and 22 % (n = 12), respectively (p < 0.0001). The vast majority of residual tumors were poorly differentiated (Gleason score ≥8). Endocrine therapy alone was predictive of residual prostate cancer: odds ratio 7.49 (3.18–17.7), p < 0.0001. In patients with positive vs. negative biopsy the incidences of clinical events were as follows: biochemical recurrence 74 % vs. 27 % (p < 0.0001), local progression 26 % vs. 4.7 % (p = 0.002), distant recurrence 17 % vs. 9.4 % (p = 0.27), clinical recurrence 36 % vs. 13 % (p = 0.006), cancer-specific death 19 % vs. 9.7 % (p = 0.025). In multivariable analysis, biochemical recurrence was significantly associated with residual cancer: hazard ratio 2.69 (1.45–4.99), p = 0.002, and endocrine therapy alone hazard ratio 3.45 (1.80–6.62), p < 0.0001.
Radiotherapy combined with hormones improved local tumor control in comparison with endocrine therapy alone. Residual prostate cancer was significantly associated with serum prostate-specific antigen recurrence, local tumor progression, clinical recurrence, and cancer-specific death in univariable analysis. Residual cancer was predictive of prostate-specific antigen recurrence in multivariable analysis.