PHOTON NEUTRON MIXED-BEAM RADIOTHERAPY OF LOCALLY ADVANCED PROSTATE-CANCER

Purpose: In this article we present the results of mixed-beam, photon/ neutron radiation therapy in 45 patients with locally advanced, bulky, or postoperative recurrent prostate cancer treated at the University of Chicago between 1978 and 1991. Survival, disease-free survival, loc al control, and long-term complications are analyzed in detail. Method s and Materials: Between 1978 and 1991, 45 patients with locally advan ced (> 5 cm Stage B2, Stage C, or Stage D1) prostate cancer underwent mixed-beam (photon/neutron) radiation therapy. Forty percent of the tr eatment was delivered with neutron irradiation at either the Universit y of Chicago or Fermilab. Sixty percent of treatment was delivered wit h photons at the University of Chicago. Initially, the whole pelvis wa s irradiated to 50 photon Gy equivalent. This was followed by a boost to the prostate for an additional 20 photon Gy equivalent. Results: Th e median follow-up for patients in this series is 72 months. The overa ll 5-year actuarial survival was 72%, and the 5-year disease-free surv ival was 45%. Thus far, 18 patients have died. Eleven patients have di ed from prostate cancer and 7 from other medical illness. Twenty-seven patients are alive, and 12 of these patients have recurrent and or me tastatic disease. The local control rate was 89% (40 out of 45). Histo logic material was available on 18 patients following treatment (i.e., prostate biopsy in 16 patients and autopsy in 2 patients) acid was ne gative for carcinoma in 13 (72%). Significant Grade 3-5 complications occurred in 36% (16 out of 45) of the patients treated with mixed-beam radiation therapy and were related to dose acid beam quality. Factors related to survival, disease-free survival, local central, and compli cations are analyzed. Conclusions: The survival and local control resu lts of mixed-beam radiation therapy at the University of Chicago appea r to be superior to those series using photon radiation in patients wi th locally advanced prostate carcinoma. Mixed-beam radiation therapy s hould remain an alternative to studies using dose escalation or implan t techniques as a method to increase local control and survival at ins titutions with this capability. However, appropriate plans with high-e nergy neutrons are necessary to minimize complications.