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