Effect of rectal enemas on rectal dosimetric parameters during high-dose-rate vaginal cuff brachytherapy

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

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.

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: D_0.1 cc: 6.6 vs. 7.21 Gy; D_1 cc: 5.35 vs. 5.52 Gy; D_2 cc: 4.67 vs. 4.72 Gy, before and after rectal cleaning, respectively (where D_x cc is the dose to the most exposed x cm³). 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 D_5 %, D_25 %, and D_50 %. In contrast, in patients whose rectal volume decreased, significance was only seen for D_25 % and D_50 % (D_x % dose covering x % of the volume). In the latter patients, nonsignificant reductions in D_2 cc, D_5 cc and V_5 Gy (volume receiving at least 5 Gy) were observed.

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