DECREASING GASTROINTESTINAL MORBIDITY WITH THE USE OF SMALL-BOWEL CONTRAST DURING TREATMENT PLANNING FOR PELVIC IRRADIATION

Small bowel tolerance is a major dose-limiting factor in treating the pelvis with radiation therapy (RT). The use of small bowel contrast during RT simulation is one technique used to localize the bowel and identify the treatment plan that would exclude the greatest volume. To determine the influence of treatment planning with oral contrast on gastrointestinal injury, acute and chronic small bowel morbidity was analyzed in 115 patients with endometrial and rectal carcinoma who received postoperative radiation therapy at the Fox Chase Cancer Center. Mean and median time of follow-up were 31 and 27 months, respectively. Acute diarrhea was seen in 82% of the patient population. Ten percent of patients experienced major complications requiring hospitalization. Ninety-three percent of patients simulated without contrast experienced side effects compared to 77% of patients simulated with contrast (p = .026). There was an increased incidence of chronic complications in patients who were not simulated with contrast dye (50% vs 23%, p = .014). Median duration of minor side effects was 4 months for patients planned without oral contrast and 1 month for patients who had contrast at the time of simulation (p = .036). The superior aspect of the treatment field was determined to be at a more inferior location in patients simulated with contrast, thereby excluding small bowel from treatment. Seventy-four percent of patients simulated without contrast had the upper border of the field placed at the superior aspect of the sacroiliac joint or above, compared to only 40% of patients planned with oral contrast (p = .002). This study has demonstrated decreased complications (both overall and chronic) as well as a change in the location of the treatment field with the use of small bowel contrast. Multivariate analysis revealed that both the use of oral contrast (p = .026) and a lower superior border of the treatment field (p = .007) were predictive for fewer sequelae to RT, indicating that planning with contrast leads to changes in the technical delivery of RT other than field placement (e.g., block placement). The reduced incidence and duration of small bowel morbidity may be in part caused by alterations of the treatment plan made when the small bowel is visualized at the time of simulation. It is therefore recommended that oral small bowel contrast be used during treatment planning for pelvic irradiation.