A phase II study of [90Y] 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 prostate 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 prostatectomy as evidenced solely by a rising serum PSA and evidence of soft tissue lesions outside the prostatic fossa detected by an [111I]indiumcapromab pendetide scan received an infusion of 10 mg of capromab pendetide labeled with 9 mCi/m2 of [90Y]yttrium. Serum PSA was used to measure response rate. There were no complete or partial responses by PSA criteria. Significant unexpected bone marrow toxicity developed in the first 6 of 8 patients treated. The last two patients received co-infusion of edetate calcium disodium in an effort to decrease marrow suppression. In these two patients less marrow toxicity was seen. Repeat 111In-capromab pendetide scans were uninterpretable due to grossly altered whole-body biodistribution of the radioimmunoconjugate. Retrospective analysis of serial PSA values after closure of the study showed a decrease in the log slope PSA for seven of eight patients following radioimmunotherapy, with a statistically significant change in the mean log slope (p = 0.01). The clinical significance of this small but measurable change is uncertain. We conclude that radioimmunotherapy for occult metastatic prostate cancer using 90Y-capromab-pendetide at the dose described does not lower serum PSA, is associated with significant hematologic toxicity, and leads to complexation of the immunoconjugate following subsequent capromab pendetide infusion.

Radioimmunoscintigraphy with In-111-labeled capromab pendetide predicts prostate cancer response to salvage radiotherapy after failed radical prostatectomy.

PURPOSE: We investigated the ability of In-111-capromab pendetide to separate patients who have failed radical prostatectomy into categories of those who would versus those who would not respond to salvage radiotherapy. METHODS: Prostate-specific antigen (PSA) levels in 32 men with prostate cancer who had failed radical prostatectomy and had undergone a whole-body In-111-capromab pendetide scan were followed-up for 13 months (median) after salvage radiotherapy to the pelvis. A logistic regression model was used to determine whether the scan findings, as well as other clinical variables, were associated with a durable complete response (DCR), a nondurable response (NDR), or no response (NR). RESULTS: Sixteen of 23 (70%) men with a normal scan outside the prostatic fossa achieved a DCR after salvage radiotherapy versus two of nine (22%) who had a positive scan outside the prostate fossa and pelvis (P = .0225, Fisher's exact test). Predicted probability (95% confidence interval [CI]) that a DCR would be obtained with a normal scan was 0.88 (0.55 to 0.98); for men with a positive scan limited to the prostatic fossa it was 0.62 (0.42 to 0.79); and for men with a positive scan outside the pelvis it was 0.27 (0.09 to 0.58). No other variables before radiotherapy showed a significant association with the DCR rate. CONCLUSION: Salvage radiotherapy is statistically more likely to lead to a durable complete PSA response in men with prostate cancer who have failed radical prostatectomy and have a negative In-111-capromab pendetide scan outside the pelvis as compared with those who have a positive scan.