(ChemotherapyAdvisor) – Temsirolimus appears to demonstrate activity in chemotherapy-naïve patients with castration-resistant prostate cancer (CRPC) and is well tolerated, according to results of a Phase 2 study presented during the 2012 Genitourinary Cancers Symposium.

Chadi Nabhan, MD, of Advocate Lutheran General Hospital and Oncology Specialists, Park Ridge, IL, and colleagues reported outcomes of 18 patients who received temsirolimus 25mg weekly until disease progression. Median age was 75 years and 10 had bone and visceral disease; 77% (n=14) had Gleason ≥7 and median PSA was 211.3. Previous therapy included surgery, brachytherapy, external radiation, and androgen deprivation therapy (ADT); median time on ADT was 60 months (range, 17–240 months).

Of 16 patients evaluable by RECIST, 2 had a partial response and 9 had stable disease; clinical benefit rate was 69%. At a median follow-up of 18 months, 8 patients (44%) remained alive for a median overall survival of 13 months. Of the 15 patients for whom biochemical response data were available, 4 (26%) had a PSA decline and 1 (6%) had a >50% drop in PSA; time to PSA progression was 2 months (range, 2–12 months).

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The most commonly reported grade 3/4 toxicities were thrombocytopenia (22%), hyperglycemia (17%), hypophosphatemia (17%), fatigue (17%), pneumonia (12%), and anemia (12%). Time to radiographic progression or event in which a patient discontinued from the study was 3 months (range, 3–10 months), and time to next treatment was 4 months (range, 2–11 months). Six patients (33%) discontinued from the study without disease progression; 2 withdrew, 3 had persistent thrombocytopenia, and 1 was nonadherent.

The investigators concluded that temsirolimus did not impact QOL adversely and should be investigated further in combination therapy for this patient population.

The 2012 Genitourinary Cancers Symposium is sponsored by the American Society of Clinical Oncology, American Society for Radiation Oncology, and the Society of Urologic Oncology.