Is metronomic cyclophosphamide (mCTX) a therapeutic option for metastatic castration-resistant prostate cancer (mCRPC) patients (pts) in the era of new agents (NAs)? A retrospective multicenter Italian study.

Abstract

326 Background: Several NAs, such as abiraterone acetate (AA), cabazitaxel (CABA), and enzalutamide (ENZ), are able to significantly prolong mCRPC pts survival after docetaxel (DOC) failure. Nevertheless, all pts eventually show progressive disease with NAs and several pts may require further treatment. mCTX was considered as a feasible and tolerable therapeutic option after DOC failure before the introduction of NAs in the clinical practice. The present retrospective study describes the clinical outcomes of mCTX, used in mCRPC pts after the failure of both DOC and at least one NA. Methods: We retrospectively reviewed the clinical records of all mCRPC pts treated in 8 Italian hospitals after the introduction of NAs in the clinical practice. We considered as eligible for the present analysis all pts who received mCTX after DOC and at least one NA. All pts were treated with CTX 50 mg po daily until disease progression. Results: From December 2011 to June 2015, a consecutive series of 48 mCRPC pts, median age 72 yrs (56-90), with bone (94%), nodal (67%) or visceral (25%) mets, was treated with mCTX. All pts have previously received a DOC-based chemotherapy followed by only one NA in 21 cases, two NAs in 20, and all three NAs in 7. The median duration of the treatment was 10.4 wks (range 3.6-61.1). Recorded grade 3-4 toxicities were: anemia (5 pts), leucopenia (1), thrombocytopenia (2), fatigue (2), and anorexia (1). Seven pts (14%) achieved a PSA reduction ≥ 50% and 2 (4%) an objective response. The median progression free survival (PFS) was 3.5 mos with 7 pts (14%) showing a PFS ≥ 9 mos. The median overall survival was 6.9 mos. Conclusions: In our experience, mCTX was a feasible and well tolerated therapeutic option in heavily pre-treated pts with very advanced mCRPC. Despite its activity was limited, the clinical outcomes of this cheap treatment are similar to those observed with NAs administered in third/fourth line with a quote of pts experiencing a prolonged disease control. Prospective studies are needed to define the therapeutic role of mCTX after NAs in mCRPC pts.