Do prostatic biopsies 12 months or more after external irradiation for adenocarcinoma, Stage III, predict long-term survival?

Serial biopsies of the prostate after high dose external irradiation for adenocarcinoma show a gradual disappearance of the neoplastic cells. With such treatment, results of the biopsies do not have any short term prognostic significance. However, positive biopsies 12 months or more after treatment are reputed to be an unfavorable sign for long-term survival. From August, 1970 through February, 1974, 46 consecutive patients with locally advanced (Stage III, C, or T3 and T4) adenocarcinoma of the prostate underwent external irradiation with 2 MV X rays or cobalt-60 teletherapy. The technique included parallel, opposed, 14 X 14 cm anterior and posterior fields, and a 10 X 14 cm perineal field. The center of the prostate received a total dose of 70 Gy in 30-37 fractions in 43 to 56 days. Details of the dosimetry reveal inhomogeneity of the dose of +/- 7% within an enlarged prostate. With a median follow-up of 8 years, the actuarial survival rates, uncorrected for death from intercurrent disease, are 69% at 5 years and 49% at 10 years. Biopsies of the prostate 12 months or more after treatment were available from 31 patients: 19 had one or more positive biopsies and 12 had consistently negative biopsies; the survival curves are identical for those with and those without positive biopsies. Prostatic biopsies obtained 24 months or more after treatment were available from 21 patients: 10 had positive and 11 had negative biopsies; the survival curves are identical for those with and without residual cancer cells. Following adequate irradiation of patients with locally advanced adenocarcinoma of the prostate, the results of biopsies obtained one or two years after treatment do not predict long-term survival.