IMPACT OF A MULTILEAF COLLIMATOR ON TREATMENT MORBIDITY IN LOCALIZED CARCINOMA OF THE PROSTATE

Purpose: To evaluate the effectiveness of variable multileaf collimati on, three-dimensional treatment planning, and computer-controlled conf ormal radiation therapy of prostate cancer. Methods and Materials: Two hundred and forty-five patients with locally advanced prostate cancer have completed treatment over a 9-year time span using a multileaf co llimator and conformal treatment techniques on the University of Washi ngton cyclotron. All patients had three-dimensional treatment planning with computed tomography scans in the treatment position, and had tre atment fields individually shaped to the target volume with a continuo usly variable multileaf collimator. Treatment was delivered under comp uter control with network transfer of the multileaf collimator setting s from the treatment planning computer to the cyclotron control system . Results: The multileaf collimator combined with three-dimensional tr eatment planning results in elegant dose distributions. These neutron dose distributions resulted in a reduced local/regional tumor failure rate vith no increase in complications when compared to control treatm ent with photons in a randomized trial. Neutron treatment delivered at other institutions without conformal beam shaping resulted in the sam e improvement in local-regional tumor control rates, but was associate d with a significantly higher normal tissue complication rate than see n with conformal neutron beam delivery techniques (grade 3 and 4 cumul ative late normal tissue toxicity rates of 39% vs. 10%, p = 0.0007). C onclusions: Conformal treatment of prostate cancer using a multileaf c ollimated neutron beam results in increased local/regional tumor contr ol rates with low normal tissue toxicities. This experience is directl y applicable to the conformal treatment of prostate cancer with photon s.