Phase II trial of combination therapy with intravenous carboplatin (C) and oral everolimus (EVE) and prednisone (P) in docetaxel-pretreated (DP) metastatic castrate-resistant prostate cancer (mCRPC): A Prostate Cancer Clinical Trial Consortium study.

Abstract

156 Background: Platinum based therapies have demonstrated efficacy in DP mCRPC. EVE demonstrated preclinical efficacy in chemotherapy resistant prostate cancer models. Clinical synergy was noted between C and EVE, hence a phase II trial of the combination was conducted. Methods: Primary endpoint was time to progression (TTP). Progression was defined per RECIST criteria for measurable disease (MD), or skeletal event, or > 2 new areas of bone metastases. DP mCRPC patients with adequate renal and liver function, and performance status of 0 or 1 were eligible. Intravenous C at target AUC of 5 on day 1, and oral EVE 5mg once daily and P 5mg twice daily were administered in 21 day cycles. PSA was assessed every 21 days and radiologic response was assessed every 3 cycles. Secondary endpoints included overall survival (OS), correlation of TTP and PSA response, with markers such as phopho mTOR, pAKT, p70S6 and circulating tumor cells (CTC). Results: 26 patients (pts) enrolled, including 8 African Americans, and accrual is complete. Median age was 69 years (range 54-86). Median pretherapy PSA was 190 ng/ml (range 13 - 2174). 18 pts (69%) had bone pain. Gleason score was > 8 in 18 pts. 19 pts had measurable disease of which 15 had MD progression, 18 had bone scan progression, and 2 had PSA-only progression. 124 cycles have been administered; median 3 cycles (range 1 - 16). The predominant grade 3 or 4 toxicities were thrombocytopenia in 8 pts, pulmonary embolism in 2 and neutropenia in 3. No treatment related deaths occurred. Of 26 pts who are response evaluable, 4 (15%) had a > 30% PSA decline and 1 had a >90% PSA decline. Of 19 pts with MD, 8 had stable disease and no objective responses were observed. The median TTP and OS were 2.5 months (90% CI: 1.8 - 4.3), and 12.5 months (90% CI: 6.7 - 16.1), respectively. Correlative studies including pharmacokinetic and pharmacodynamic evaluations are ongoing, and will be reported. Conclusions: The combination was tolerable but revealed modest clinical efficacy. Biomarker evaluation may help identify a subset likely to benefit from mTOR inhibition strategy in mCRPC. Clinical trial information: NCT01051570.