Effect of rectal enemas on rectal dosimetric parameters during high-dose-rate vaginal cuff brachytherapy: A prospective trial.

PURPOSE: To evaluate the effects of rectal enemas on rectal doses during postoperative high-dose-rate (HDR) vaginal cuff brachytherapy (VCB).

PATIENTS AND METHODS: This prospective trial included 59 patients. Two rectal cleansing enemas were self-administered before the second fraction, and fraction 1 was considered the basal status. Dose-volume histogram (DVH) values were generated for the rectum and correlated with rectal volume variation. Statistical analyses used paired and unpaired t-tests.

RESULTS: Despite a significant 15 % reduction in mean rectal volume (44.07 vs. 52.15 cc, p = 0.0018), 35.6 % of patients had larger rectums after rectal enemas. No significant rectal enema-related DVH differences were observed compared to the basal data. Although not statistically significant, rectal cleansing-associated increases in mean rectal DVH values were observed: D0.1 cc: 6.6 vs. 7.21 Gy; D1 cc: 5.35 vs. 5.52 Gy; D2 cc: 4.67 vs. 4.72 Gy, before and after rectal cleaning, respectively (where Dx cc is the dose to the most exposed x cm(3)). No differences were observed in DVH parameters according to rectal volume increase or decrease after the enema. Patients whose rectal volume increased also had significantly larger DVH parameters, except for D5 %, D25 %, and D50 %. In contrast, in patients whose rectal volume decreased, significance was only seen for D25 % and D50 % (Dx % dose covering x % of the volume). In the latter patients, nonsignificant reductions in D2 cc, D5 cc and V5 Gy (volume receiving at least 5 Gy) were observed.

CONCLUSION: The current rectal enemas protocol was ineffective in significantly modifying rectal DVH parameters for HDR-VCB.