THE TREATMENT OF PROSTATE-CANCER BY CONVENTIONAL RADIATION-THERAPY - AN ANALYSIS OF LONG-TERM OUTCOME

Purpose: To assess the long-term outcome of conventional external beam radiation therapy in the management of clinically confined prostate c ancer and to examine the proposition that radiation accelerates tumor growth in those who fail treatment. Methods and Materials: One thousan d and forty-four men with T1-4NxMO prostate cancer treated by conventi onal external beam radiation therapy at the Massachusetts General Hosp ital between 1977 and 1991 were analyzed. Median follow-up was 49 mont hs, Failure was defined as: two sequential rises in serum prostate spe cific antigen (PSA) level; or a PSA >1 ng/ml 2 or more years after rad iation; or any clinical failure. Kaplan-Meier actuarial analyses were used to assess outcome. Results: At 10 years only 40% of the T1-2 grou p remained disease free. subdivided by grade, the well-differentiated tumors (Gleason 1-2) exhibited a 53% actuarial 10-year disease-free su rvival, moderately differentiated (Gleason 3) 42%, and poorly differen tiated (Gleason 4-5) 20%. The corresponding values for the T3-4 men we re 33% for Gleason 1-2, 20% for Gleason 3, and 10% for Gleason 4-5. Ov erall the value for T3-4 tumors was 18% at 10 years. On relapse the me dian PSA doubling times for the T1-2 patients were predicted by histol ogy: 18.8 months for Gleason 1-2 patients; 11.1 months for Gleason 3; and 9.6 months for Gleason 5. Significant differences were found betwe en the Gleason 3 and the Gleason 4-5 groups (p = 0.04) and the Gleason 1-2 and the Gleason 4-5 groups (p = 0.03). A wide range of doubling t imes was seen within each grade group. When compared with recently rep orted data on selected T1-2 patients who were managed by expectant obs ervation there was no advantage over the first decade (and certainly n o disadvantage) in terms of metastasis-free survival or disease-specif ic survival for the irradiated Gleason 1-3 patients. However, a gain w as seen for those with Gleason 4-5 tumors. Conclusion: Less than half of the T1-2NxMO and less than one-fifth of the T3-4NxMO patients recei ving conventional radiation therapy were biochemically disease free at 10 years. The PSA doubling times on relapse show a wide variation. Gr ade was important in determining the rate of relapse suggesting that r adiation does not induce a homogeneous acceleration of prostate turner s. A metastasis-free and disease-specific survival advantage was found for the poorly differentiated tumors when compared with similar patie nts reported in the literature who were managed initially by observati on.