Continuous infusion fluorouracil (5FU) in heavily pre-treated mCRPC patients.

Abstract

257 Background: Pts with mCRPC resistant to novel hormones (abi/enza), and taxane chemotherapy are challenging. Extensive pre-treatment typically poses an issue for clinical trials, and there is no consensus regarding how to manage patients who no longer respond to conventional therapies but maintain a good performance status. Methods: 13 mCRPC pts were treated with 5FU at 200mg/m2 continuous infusion as a novel treatment option for those with heavily pretreated mCRPC. Data was retrospectively collected at Tulane Cancer Center for patient treatment history, and laboratory parameters. Results: All treated patients had prior exposure to an average of 8.7 lines of treatment. 5FU was used as median 8th line therapy. All pts had extensive bony disease and 6 had liver involvement. Median PSA at start of treatment was 356 ng/dL. 5 pts progressed within a month of initiation of therapy, and 2 pts did not respond. 8 (61%) patients had treatment for >1 month with 6 having >30% PSA reduction, 4 with a >50% PSA reduction and 2 with a >90% PSA reduction (Table). Median time on therapy was 4.5 months with 2 patients remaining on treatment for >6 months despite multiple pretreatments and far advanced disease. 5FU was well tolerated with improvement in both performance status and symptoms in several patients. Conclusions: Continuous 5FU is active in select highly pretreated pts and targets folate metabolism via inhibition of thymidylate synthase. It is one of the few chemotherapies that can be administered with little myelosuppression, an important issue in far-advanced pts. Prostate specific membrane antigen (PSMA) expression is upregulated in CRPC, especially after abi/enza treatment. PSMA hydrolyzes polyglutamated folates and functions as a folate transporter; its over-expression stimulates both folate transport and prostate cancer cell line growth. We hypothesize that 5FU, functioning as an anti-folate, antagonizes the downstream effects of PSMA over-expression. PSA data for pts on treatment > 1 month. [Table: see text]