Zagars G K, von Eschenbach A C, Ayala A G
Department of Clinical Radiotherapy, University of Texas M. D. Anderson Cancer Center, Houston 77030.
Cancer. 1993 Sep 1;72(5):1709-25. doi: 10.1002/1097-0142(19930901)72:5<1709::aid-cncr2820720535>3.0.co;2-o.
The outcome of radiation therapy for localized prostate cancer depends on many pretreatment variables that are interrelated in complex ways. A multivariate analysis of 874 cases of prostate cancer treated between 1966 and 1988 was conducted. The median length of the follow-up period after radiation therapy was 6.7 years.
The disease outcome and rate of survival was analyzed with the proportional hazards model for patients with stage A2 (104), stage B (168), or stage C (602) prostate cancer treated with radiation therapy as the only primary treatment.
Local recurrence rates were 12%, 24%, and 33% at 5, 10, and 15 years, respectively. In multivariate analysis, stage (A2 vs. B+C) and pathologic grade (1 + 2 vs 3 + 4) were independently related to local recurrence. At 10 years local control had been achieved in 79% of favorable cases (stage A2 or stage B/C, grade 1), but in only 62% of unfavorable cases (stage B/C, grade 4). Metastatic relapse rates were 25%, 38%, and 47% at 5, 10, and 15 years, respectively. Factors that independently correlated with metastasis were high pathologic grade, transurethral resection in stage C, elevated acid phosphatase levels, and being 60 years of age or younger. A favorable group of cases (stage A2/B, grade 1 or stage C, grade 1, no transurethral resection, older than 60 years of age) had a metastatic rate of only 10% after 10 years, whereas an unfavorable group (largely stage C, grades 3/4) had a metastatic rate approaching 70%. The overall survival rate was 77%, 49%, and 32% at 5, 10, and 15 years, respectively. Pathologic grade (1 vs 2 + 3 vs 4) and transurethral resection in stage C correlated with survival. A favorable group of patients (stage A2/B or stage C and grade 1) had a normal survival expectation of 15 years. An unfavorable group consisting of grade 4 tumors had a survival rate of less than 20% at 10 years.
The complexity and long natural history of prostate cancer demand careful stratification and follow-up examination to evaluate treatment results. The study of adjuvants to improve the local effectiveness of radiation and to mitigate the high metastatic rates in unfavorable local disease are urgent priorities.
