UroToday - In the Annals of Oncology, Dr. Dror Michaelson and associates reported Phase II data on the efficacy and safety of the tyrosine kinase inhibitor sunitinib in patients with castration-resistant prostate cancer (CRPC). Sunitinib inhibits vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF), both elevated in prostate cancer (CaP).

Two groups of patients were studied; group A, which was chemotherapy na??ve and group B, which had failed docetaxel. The primary endpoint was PSA decline >50% from baseline. Secondary endpoints included objective response rate, safety, tolerability and serum biomarkers. Treatment was in 6-week cycles, consisting of 50mg daily for 4 weeks followed by 2 weeks off. Concurrent treatment with bisphosphonates was permitted.

Seventeen men in each group had data available for analysis. Only one patient in group A, and one patient in group B demonstrated a >50% PSA decline. Fourteen of 34 men had some PSA decline and 8 men (34%) had a >30% PSA decline. At 12-week analysis it was noted that radiographic improvements were present in some patients who nevertheless had increasing PSA levels. Based upon not having 2 or more PSA response criteria met, the study enrollment was not continued. Adverse events were primarily grade 1 or 2 and included nausea, fatigue, anorexia, taste disturbance, vomiting, diarrhea and skin rash. Regarding biomarkers, sVEGFR2, PDGFaa, and leptin all decreased but did not correlate with PSA.

Dror Michaelson M, Regan MM, Oh WK, Kaufman DS, Olivier K, Michaelson SZ, Spicer B, Gurski C, Kantoff PW, Smith MR
Ann Oncol. 2009 May;20(5):913-20.
doi:10.1093/annonc/mdp111

Written by UroToday Contributing Editor Christopher P. Evans, MD, FACS

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