Correlation Between Dosimetric Parameters and Late Rectal and Urinary Toxicities in Patients Treated With High-Dose-Rate Brachytherapy Used as Monotherapy for Prostate Cancer

To evaluate the correlation between dosimetric parameters and late rectal and urinary toxicities in high-dose-rate brachytherapy (HDR-BT) used as monotherapy for prostate cancer.The data of 83 patients treated with HDR-BT alone for prostate cancer from 2001 through 2005 at Osaka University Hospital were analyzed. Median follow-up time was 36 months (range, 18-70). The total prescribed dose was 54 Gy in nine fractions over 5 days. Correlation between dosimetric parameters and late toxicities was examined.The means of V30, V40, V50, V60, V70, D1cc, D2cc, D5cc, and D10cc of the rectum were significantly higher in 18 patients who presented with late rectal toxicity (Grades 1-3 rectal bleeding) than in the other 65 patients who did not. A significant difference was observed for D1cc-10cc but not for D5-90. The statistically most significant difference was observed for V40 and D5cc. Late rectal toxicity rate was significantly higher for patients with rectal V40or= 8 cc than those with the rectal V408 cc (42% vs. 8%; p0.001), as well as for patients with rectal D5ccor= 27 Gy compared with those with rectal D5cc27 Gy (50% vs. 11%; p0.001). Dosimetric parameters of the urethra of 15 patients with late urinary toxicity were not significantly different from the 68 patients without toxicity.Rectal V408 cc and D5cc27 Gy may be dose-volume constraints in HDR-BT used as monotherapy for prostate cancer.