Acute diarrhea during pelvic irradiation: Is small-bowel volume effect different in gynecologic patients with prior abdomen operation or not?

Objective. To evaluate volume effect of small bowel for diarrhea during pelvic irradiation in gynecologic patients with or without prior abdomen operation. Methods. From January 1996 through December 2003, 759 patients undergoing 4-field pelvic irradiation for cervical or uterine cancer were analyzed. Whole pelvic (WP), modified whole pelvic (MWP), or lower pelvic (LP) irradiation were delivered initially. According to contrast medium within small bowel in simulation films, we categorized the small-bowel volume of full dose related to WP fields as small-volume and large-volume groups. We recorded the severity of diarrhea until 39.6 Gy/22 fractions of pelvic irradiation. The actuarial rates of overall and moderate to severe diarrhea were compared among different groups. Results. Significantly more large-volume distribution (85%) was noted in patients >60 years without prior operation (P < 0.001). Large-volume distribution was 53%, 65%, and 82% in post-operative patients with no diarrhea, mild diarrhea, and moderate to severe diarrhea (P = 0.002), respectively. The corresponding rate was 79%, 77%, and 80% in patients without prior abdomen operation (P = 0.869). In multivariate analysis, prior operation with LP fields (P = 0.005) and prior operation with small volume (P = 0.031) were significantly protective factors for overall diarrhea. The latter was also a protective factor for moderate to severe diarrhea (P = 0.026). Prior operation could diminish overall diarrhea in patients without simultaneous large-field (WP or MWP) and large-volume. Large volume was a significant factor of overall (P = 0.014) and moderate to severe (P = 0.004) diarrhea in large-field patients with operation. The volume effect did not exist in those patients without operation. Conclusion. Age and operation can change small-bowel distribution. Prior operation may attenuate diarrhea if irradiated volume of small bowel is small. There is a volume effect in post-operative rather than non-operative patients receiving large-field irradiation. More practical dose-volume evaluation of small bowel may be applied for volume effect in gynecologic patients without prior operation.