Purpose: The Scandinavian Prostate Cancer Group-7 randomized trial demonstrated a survival benefit of combined endocrine therapy and external-beam radiotherapy over endocrine therapy alone in patients with high-risk prostate cancer. In a subset of the study population, the incidence and clinical implications of residual prostate cancer in posttreatment prostate biopsy specimens was evaluated.
Methods and materials: Biopsy specimens were obtained from 120 of 875 men in the Scandinavian Prostate Cancer Group-7 study.
Results: 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.
Conclusions: 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.
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