A phase II study of [Y-90] yttrium-capromab pendetide in the treatment of men with prostate cancer recurrence following radical prostatectomy

There is currently no curative therapy for men who have disseminated prosta te cancer following failed radical prostatectomy. The purpose of this trial was to investigate systemic radioimmunotherapy in these men. Eight patients with occult metastatic prostate cancer following radical pro statectomy as evidenced solely by a rising serum PSA and evidence of soft t issue lesions outside the prostatic fossa detected by an [I-111]indium-capr omab pendetide scan received an infusion of 10 mg of capromab pendetide lab eled with 9 mCi/m(2) of [Y-90]yttrium. Serum PSA was used to measure respon se rate. There were no complete or partial responses by PSA criteria. Significant un expected bone marrow toxicity developed in the first 6 of 8 patients treate d The last two patients received co-infusion of edetate calcium disodium in an effort to decrease marrow suppression. In these two patients less marro w toxicity was seen. Repeat In-111-capromab pendetide scans were uninterpre table due to grossly altered whole-body biodistribution of the radioimmunoc onjugate. Retrospective analysis of serial PSA values after closure of the study showed a decrease in the log slope PSA for seven of eight patients fo llowing radioimmunotherapy, with a statistically significant change in the mean log slope (p = 0.01). The clinical significance of this small but meas urable change is uncertain. We conclude that radioimmunotherapy for occult metastatic prostate cancer u sing Y-90-capromab-pendetide at the dose described does not lower serum PSA , is associated with significant hematologic toxicity and leads to complexa tion of the immunoconjugate following subsequent capromab pendetide infusio n.