Purpose: To evaluate the feasibility of administering sunitinib in combination with androgen deprivation therapy and external-beam intensity modulated radiation therapy (XRT) in patients with localized high-risk prostate cancer.
Methods and materials: Seventeen men with localized adenocarcinoma of the prostate with cT2c-cT4 or Gleason 8-10 or prostate-specific antigen >20 ng/mL received initial androgen deprivation (leuprolide 22.5 mg every 12 weeks plus oral bicalutamide 50 mg daily) for 4-8 weeks before oral sunitinib 12.5, 25, or 37.5 mg daily for 4 weeks as lead-in, then concurrently with and 4 weeks after XRT (75.6 Gy in 42 fractions to prostate and seminal vesicles). A 3+3 sequential dose-escalation design was used to assess the frequency of dose-limiting toxicity (DLT) and establish a maximal tolerated dose of sunitinib.
Results: Sunitinib at 12.5- and 25-mg dose levels was well tolerated. The first 4 patients enrolled at 37.5 mg experienced a DLT during lead-in, and a drug interaction between sunitinib and bicalutamide was suspected. The protocol was revised and concurrent bicalutamide omitted. Of the next 3 patients enrolled at 37.5 mg, 2 of 3 receiving concurrent therapy experienced DLTs during radiation: grade 3 diarrhea and grade 3 proctitis, respectively. Only 1 of 7 patients completed sunitinib at 37.5 mg daily, whereas 3 of 3 patients (25 mg as starting dose) and 3 of 4 patients (25 mg as reduced dose) completed therapy.
Conclusions: The feasibility of combined vascular endothelial growth factor receptor (VEGFR)/platelet-derived growth factor receptor (PDGFR) inhibitor therapy, androgen deprivation, and radiation therapy for prostate cancer was established. Using a daily dosing regimen with lead-in, concurrent, and post-XRT therapy, the recommended phase 2 dose of sunitinib is 25 mg daily.
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