A phase II study of sunitinib (SU) for maintenance therapy in metastatic castration-resistant prostate cancer (mCRPC) after response to docetaxel (D).
151 Background: After treatment with D based chemotherapy, there is currently no standard therapy although new options are emerging. Due to its mechanism of action, acceptable toxicity profile and simple administration, SU has potential for therapeutic activity in the setting of maintenance therapy for patients with mCRPC who have responded to D based chemotherapy. Methods: Patients with mCRPC who had evidence of responding or stable disease at completion of D treatment were enrolled in this phase II multicentre trial. Patients received 50mg of SU daily on 4 week on/2 week off cycles. The primary endpoint was effect of SU maintenance on PFS. Because of potential effects of SU on PSA kinetics, clinical progression was defined independent of PSA. PSA response rate was a secondary endpoint. PSA-progression (PSA-P) was defined as a 25% PSA increase over baseline. Results: Thirteen patients have been enrolled and treated to date. Mean age was 63 years (47-76). ECOG scores of 0, 1, and 2 were reported for 4, 8 and 1 patients respectively. Mean number of prior cycles of D given was 9.5. A total of 28 cycles of SU were administered. A total of 291 adverse events (AEs) were recorded, of which 66%, 27%, and 7% were classified as Grades 1, 2, and 3, respectively. No Grade 4 AEs were seen. AEs were of a type and severity expected for SU. The most frequent grade 3 AEs were fatigue (n=3) and hand foot syndrome (n=3). No PSA responses have been documented. Most patients had immediate PSA increases without evidence of clinical progression. The mean PSAs increased by 159%, 396%, and 853% in Cycles 1, 2, and 3, respectively, corresponding to p-values of 0.18, 0.03, and 0.01 when compared to the PSA-P threshold of 25%. The trial will continue to complete its planned accrual of 26 evaluable patients and updated results, along with PFS, will be presented at the meeting. Conclusions: SU is well tolerated as maintenance therapy after D in men with mCRPC, with a predictable side-effect profile. PSA values after treatment with SU may not reflect progression in patients with mCRPCas significant increases were observed as early as Cycle 2 without clinical evidence of worsening disease. [Table: see text]