Results Of A Phase Ii Dose Escalation Study Of Neutron And Photon Irradiation In Patients With Locally Advanced And/Or Poorly Differentiated Prostate Cancer

This study was performed to determine the rates of toxicity, survival and disease-free survival in patients with locally advanced and/or poorly differentiated prostate cancer receiving 11 N Gy + 40 or 46 Gy of photons. Ninety-seven patients were entered on this IRB approved Phase II dose-escalation study of sequential neutron and photon irradiation. Patients received 11 N Gy followed by 40 Gy photons in 20 fractions (67 patients) or 46 Gy in 40 fractions of 1.15 Gy bid. Thirty-six patients were African American. The median pre-treatment PSA level was 14 ng/mL (range 1.1 to 330). Eight patients had a Gleason Score of ≤6, 24 were = 7 and 65 were ≥8. Forty-three patients had Stage T1/2 disease. Sixty-four had Stage T3/4. The median follow-up was 56 months (range 4 to 96 months). Thirty-nine patients (40%) have experienced biochemical failure. Twelve patients have died during the follow-up period. The 5-year actuarial rate of Overall Survival was 88%. The 5-year Disease-Free Survival was 53%. The 5-year actuarial rates of Grade 2 and 3 GU morbidity were 13 and 10%, respectively. These rates were 20% and 7% for Grade 2 and 3 GI complications, respectively. This study has demonstrated that 11 N Gy can be given with moderate GI and GU toxicity. The rates of complications were intermediate between our prior Phase II studies of 9, 10 and 15 N Gy. At 11 N Gy we have reached our dose limiting toxicity. Since the rates of disease control seem encouraging, further studies at this dose level will look at using IMRT planning of the neutron and photon irradiation as a way of further reducing complications while maintaining high disease probabilities