The influence of local control on metastatic dissemination of prostate cancer treated by external beam megavoltage radiation therapy.

The influence of local control on metastatic dissemination was analyzed in 601 patients with clinically staged A2 to C prostate cancer treated by high-energy external beam radiation therapy who did not undergo hormonal manipulation before disease progression. Median follow-up for surviving patients was 7.7 years. Ninety-three patients had locally recurrent disease. The actuarial incidence of metastases in these patients (70% at 13 years) was significantly higher than in the 508 patients without local failure (40% at 13 years, P less than 0.001). High stage, high grade, prior transurethral resection, elevated acid phosphatase, disease fixation to the pelvic sidewall, and failure to perform a baseline bone scan correlated positively with the occurrence of metastases. However, except for a slight excess of Stage C, none of the metastatic predictors were more common in patients who failed locally than in those who did not. The Stage C preponderance does not account for the difference in incidence of metastases between the two groups, in as much as metastases were significantly more common in Stage C when disease recurred locally than when it did not. Thus, local control of prostate cancer does decrease the likelihood of metastatic disease. Moreover, patients with local control experienced a significantly better disease-specific survival than patients who failed locally.