Differences in dosimetry and toxicity between definitive and postprostatectomy radiation therapy.

PURPOSE: To compare the volumes of normal tissue irradiation and toxicity in patients treated with definitive radiation therapy or postprostatectomy radiation therapy.

MATERIALS AND

METHODS

Results were analyzed prospectively in 49 patients who underwent definitive or postprostatectomy radiation therapy after three-dimensional conformal treatment planning. Dose-volume histograms and the effective area irradiated were analyzed. Patient charts were reviewed and scored for acute and chronic toxicity. The mean bladder volume was 200 mL in the definitive group and 226 mL in the postprostatectomy group. The mean rectal volume was 87 mL in the definitive group and 81 mL in the postprostatectomy group.

RESULTS

The dose to 25% of the rectal volume was 91% and 86% in the definitive and postprostatectomy groups, respectively. The dose to 25% of the bladder volume was 89% in the definitive group and 82% in the postprostatectomy group. The incidence of acute and chronic gastrointestinal and chronic genitourinary toxicity was similar in both groups, but acute genitourinary toxicity in the postprostatectomy group was significantly lower (P = .026). The volume of normal tissue irradiated was similar in both groups. Also, similar doses were delivered to the normal tissue.

CONCLUSION

Differences in acute genitourinary toxicity are most likely secondary to radiation-induced prostatitis. Postprostatectomy radiation therapy is safe and is not associated with increased toxicity.