The value of serial prostate specific antigen determinations 5 years after radiotherapy: steeply increasing values characterize 80% of patients.

In 1989 we reported on 124 consecutive unselected patients in whom serial polyclonal prostate specific antigen (PSA) determinations were done after radiotherapy to the prostate for clinical stages A, B, C and D1 disease. After a PSA followup of 32 months 51% of the patients had increasing values, while 41% were stable with a mean PSA level of 2.9 ng./ml. We report an additional followup of 48 months on 113 of those patients, representing a mean overall followup of 6 years. Of the 113 patients 88 (78%) have a precipitously increasing PSA level with median doubling times of 14 (stage A), 15 (stage B), 7 (stage C) and 8 (stage D1) months, respectively, at a mean followup of 5 years after radiotherapy. A total of 23 patients (20%) appears cured with a PSA level of less than 1.7 ng./ml. at a mean followup of 9 years (median 7.7). Of the 113 patients 2 continued to have a decreasing PSA level 3 years after irradiation. Among the cured patients there was no relationship to clinical stage A, B or C cancer. We conclude that approximately 20% of the patients with clinical stages A to D1 prostate cancer can be cured by irradiation therapy. They can be identified by a low PSA level that seems to persist indefinitely. The remaining 80% of the patients in whom radiotherapy fails appear to have an accelerated growth rate suggesting tumor clonogen repopulation during radiotherapy.