Overcoming Docetaxel Resistance In Advanced Castration-Resistant Prostate Cancer (Crpc): A Phase I/Ii Trial Of The Combination Of Temsirolimus And Docetaxel

250 Background: Mechanisms of resistance to docetaxel (D) are not fully understood. Preclinical work showed that administration of temsirolimus (T) between courses of D delays the growth of PTEN deficient tumors in xenografts. (Wu et al. Cancer Res 2005) The current study aims to determine the recommended phase II dose (RPTD), toxicity, pharmacokinetics (PK) and preliminary activity of D in combination with T in CRPC patients (pts).Pts aged ≥ 18 with advanced solid tumors refractory to standard therapy, ECOG ≤2, adequate bone marrow and renal function were eligible. D was given once q. 3 weeks along with T on days 2, 9 &16. The protocol was later amended and day 9 of T omitted due to excessive myelotoxicity. A 3+3 rule dose escalation was used with the next dose levels (DL) planned: DL1: D 50mg/m2, T 15 mg; DL2: D 65mg/m2, T 15 mg; DL3: D 75mg/m2, T 15 mg; DL4: D 75mg/m2, T 25 mg. An expanded cohort for pts with CRPC who have progressed to D will enroll pts once the RPTD has been defined.To date 13 pts have been enrolled, median age = 65 (range 35-76), 9 male and 8 ECOG 0, Forty-seven cycles (median: 2; range: 1-9) were administered. The most frequent related adverse events (AEs) of all grades expressed as % of cycles were: leucopenia (80.8%), hyperglycemia (70.2%), anemia (68.1%) and hypercholesterolemia (65.9%). The most common Grade 3-4 AEs as % of cycles were: leucopenia (27.6%), neutropenia (29.7%), and hypophosphatemia (23%). Two pts in DL2 experienced dose limiting toxicities (DLT) consisting of intolerable grade 2 mucositis and febrile neutropenia respectively. DL1 was expanded and 3 additional pts treated with no DLTs. No drug-drug PK interactions were observed. Among 13 pts evaluable for response, 6 (2 pancreas, 2 CRPC, 1 rectal and 1 sarcoma) achieved stable disease. One pt with CRPC who had previously progressed on docetaxel received 9 cycles of treatment with sustained clinical benefit. The expanded cohort for CRPC patients is opened and recruiting.T and D can be safely combined at reduced doses of both agents with no PK interaction. Preliminary antitumor activity has been observed in CRPC patients. Data on the expanded cohort will be presented.