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 minimize 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 treatment parameters of patients with and without such a device. Methods and Materials: Between 1983 and 1991, 77 patients with a diagnosis of endometrial (n = 35), colorectal (n = 41), or anal carcinoma (n = 1) received adjuvant postoperative radiotherapy after undergoing treatment planning simulation with the use of small bowel oral contrast medium. Fourteen of these patients underwent surgical placement of a temporary intrapelvic 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 between the two patient groups. Results: The volume of small bowel within the initial pelvic fields receiving full dose irradiation was significantly 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 expander (p < .0001). A similar reduction of irradiated small bowel volume was 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 treatment field (p = .003). Morbidity related to placement and removal of the tissue expander was acceptable. Acute radiation-related morbidity was significantly less in patients irradiated with a tissue expander in place (p < .001). Conclusions: Placement of an intrapelvic tissue expander was correlated with decreased small bowel volume within the radiotherapy treatment field. Diminished radiation-induced acute gastrointestinal morbidity was noted with use of a tissue expander.