VOLUMETRIC-ANALYSIS OF SMALL-BOWEL DISPLACEMENT FROM RADIATION PORTALS WITH THE USE OF A PELVIC TISSUE EXPANDER

Purpose: Many techniques and devices have been used in an attempt to m inimize gastrointestinal morbidity of pelvic irradiation. The value of a temporary intrapelvic tissue expander to displace small bowel from pelvic radiotherapy fields was analyzed by comparing volumetric treatm ent parameters of patients with and without such a device. Methods and Materials: Between 1983 and 1991, 77 patients with a diagnosis of end ometrial (n = 35), colorectal (n = 41), or anal carcinoma (n = 1) rece ived adjuvant postoperative radiotherapy after undergoing treatment pl anning simulation with the use of small bowel oral contrast medium. Fo urteen of these patients underwent surgical placement of a temporary i ntrapelvic tissue expander prior to radiotherapy, and 63 patients did not. Small bowel volume within the treatment portals was measured for both initial pelvic and conedown fields for all cases, and compared be tween the two patient groups. Results: The volume of small bowel withi n the initial pelvic fields receiving full dose irradiation was signif icantly less among patients with a tissue expander. For patients with a tissue expander, mean volume receiving full dose irradiation was 25 cm3 (median 0 cm3, range 0-297 cm3), whereas the corresponding volume was 239 cm3 (median 181 cm3, range 0-943 cm3) without a tissue expande r (p < .0001). A similar reduction of irradiated small bowel volume wa s noted in the conedown fields with the use of a tissue expander (p = .07). Volumes receiving less than full dose irradiation were also less within the initial pelvic (p = .0001) and conedown (p = .002) fields with a tissue expander. Multivariate analysis of patient and treatment -related parameters showed the use of a tissue expander to be the only factor correlated with decreased small bowel volume within the treatm ent field (p = .003). Morbidity related to placement and removal of th e tissue expander was acceptable. Acute radiation-related morbidity wa s significantly less in patients irradiated with a tissue expander in place (p < .001). Conclusions: Placement of an intrapelvic tissue expa nder was correlated with decreased small bowel volume within the radio therapy treatment field. Diminished radiation-induced acute gastrointe stinal morbidity was noted with use of a tissue expander.