Minimal toxicity with 3-FAT radiotherapy of prostate cancer.

Abstract

Beam radiation with three-dimensional conformal planning appears to decrease morbidity of prostate cancer therapy. The 3-field, arc technique (3-FAT) technique was designed by computer modeling to improve radiation dose to the target and minimize dispersion to nearby organs. Toxicity was studied in patients with prostate cancer. We performed a retrospective study of 168 consecutive men with prostate cancer after 3-FAT radiotherapy with a median follow-up of 24 months. All patients, treated from 1996 through 1999 at the University of Colorado had a pathological diagnosis of cancer before irradiation. Therapy was designed with a urethrogram and planning computed tomography scan. The 3-FAT was employed using noncoplanar, rotational beams, and nonuniform blocking of portals. Patients were treated to a minimal tumor dose of 74 Gy in 37 fractions. Adverse effects were investigated. Definitive radiotherapy was given to 80% of the group, and 58% received total androgen blockade. 3-FAT produced favorable dose distributions for the rectum, bladder, femoral heads, and base of the penis. Patients routinely report minimal dysuria and frequency during treatment. There were minimal urinary complaints after irradiation and no proctitis, diarrhea, incontinence, or change in potency as a result of radiotherapy. The 3-FAT represents a technical improvement in the treatment of prostate cancer by minimizing radiation delivered to adjacent critical structures. There were minimal side effects to the rectum, bladder, and penis base despite high doses to the prostate and seminal vesicles. The large percentage of patients with preliminary prostate-specific antigen values below 1.0 portends efficacy.