Results of a phase II study of single-agent nab-paclitaxel in platinum-refractory second-line metastatic urothelial carcinoma (UC).

241 Background: There is currently no standard second-line chemotherapy for platinum- refractory UC. Both paclitaxel and docetaxel are commonly used but response rates are < 20% and no survival advantage has been shown. In this multi-institutional phase II study, we evaluated the efficacy and tolerability of a new albumin-bound nanoparticle formulation of paclitaxel, known as Abraxane (ABI-007) as a single agent in patients with platinum-refractory metastatic UC. Methods: Patients with measurable UC, progressing on or after first-line platinum-based chemotherapy were enrolled onto this two-stage trial. ABI-007 was given at 260 mg/m 2 IV q3weekly until progression. Clinical evaluation, CBC and blood chemistries were performed every cycle with restaging CT scans every 2 cycles. Results: Accrual is now complete with 48 patients enrolled. Baseline characteristics: Male: Female 40:8; median age 68; ECOG Performance Status 0:1:2, 15:24:8. 248 cycles were delivered: median 5.5 cycles/pt with 17/48 pts (35%) requiring dose reductions. Most frequent adverse events (AE) were alopecia (12%), fatigue (12%), pain (12%), neuropathy (9%) and nausea (4%). The most frequent grade 3+ AE were pain (45%), hypertension (14%), fatigue (8%), joint stiffness (5%), neuropathy (4%) and weakness (4%). Forty patients are evaluable for response: 1 (2.5%) complete response (CR), 11 (28%) partial responses (PR), 9 (23%) stable disease (SD) and 20 (49%) progressive disease. One patient was inevaluable for response, 7 patients are too early for evaluation. Conclusions: Single-agent ABI-007 was well tolerated with a response rate (CR+PR) of 33% (12/36) and a clinical benefit rate (CR+PR+SD) of 58% (21/36), representing one of the highest reported response rates to date in the second-line UC setting. These results suggest further study of ABI-007 in urothelial carcinoma is warranted. No significant financial relationships to disclose.