Use of Local 111In-Capromab Pendetide Scan Results to Predict Outcome After Salvage Radiotherapy for Prostate Cancer

Abstract

The (111)In-capromab pendetide scan (ProstaScint; Cytogen Corp., Princeton NJ) is approved by the Food and Drug Administration to evaluate increasing prostate-specific antigen (PSA) levels after radical prostatectomy. This study evaluated the role of prostate bed (111)In-capromab pendetide scan findings to predict response to salvage radiotherapy (RT). Forty patients who had PSA recurrence after radical prostatectomy and a (111)In-capromab pendetide scan immediately before salvage prostate bed RT (median, 66 Gy) were identified from the Duke Prostate Center database. Patients with distant uptake of capromab pendetide or long-term androgen deprivation therapy were excluded. Median follow-up after salvage RT was 2.7 years. Patient demographic, clinical, and pathologic characteristics; PSA values; and (111)In-capromab pendetide scan results were retrospectively analyzed. A PSA failure after salvage RT was defined as PSA level greater than 0.2 ng/ml. Data were combined with other published results in a secondary pooled analysis of 106 patients. (111)In-Capromab pendetide findings included 20 patients with negative scan results and 20 with locally positive scan results. Two-year progression-free survival rates were 60% for patients with a negative scan result and 74% for those with a locally positive scan result (p = 0.49). Combined analysis did not show a difference in outcome based on local (111)In-capromab pendetide scan result. For patients without distant signal detected by using (111)In-capromab pendetide scan, patients with locally positive scan findings did not have statistically different progression-free survival than those with a negative scan result, suggesting that salvage RT may be successful in patients with either a locally positive or negative (111)In-capromab pendetide scan result.