Irradiated Small Bowel Volume Research Articles

150 Construction and first experience with a customized “belly board” mould to minimize the volume of small bowel in the irradiation of pelvic malignancies

Radiation enteritis is a common complication of radiotherapy for pelvic malignancies, often requiring medical therapy, breaks of the treatment and sometimes the hospitalization or a surgical intervention. The volume of irradiated small bowel (SB) is considered one of the most important factors in determining gastro-intestinal side effects. Numerous techniques, principally based on the reduction of the irradiated SB volume have been applied to avoid or decrease radiation enteritis. We have realized a customized "belly board" as a bowel minimization device, modifying the original technique of Shanahan (<i>IJROBP</i> 1989,17,187–88). We use a polyurethane foam mould to place and immobilize the patient in prone position with anterior lower abdominal wall compression. A block of polystyrene in the shape of a reverse pyramid is placed under the superior abdomen during the solidification of the mould to obtain a hole for the displacement of the SB. From October 1994 to March 1995, we have utilized such device in 28 consecutive patients irradiated for pelvic tumours. The mean high dose SB volume irradiated was 56.2 cm³ (range 0–390) and the partial dose SB volume was 218.5 cm³ (range 0–588). This technique permits not only the displacement of the SB (favoured also by recommended bladder distension) minimizing the irradiated SB volume, but also contribute to the immobilization of the patient in a comfortable and repeatable position.

The prevention of radiation-induced small bowel complications.

Moderate dose pelvic radiotherapy is associated with a 5% severe complication risk related to the small bowel. Strictures and/or fistulation can occur many years after treatment. These complications are difficult to treat, and surgical treatment (excision, bypass) bears a significant morbidity risk. The risk of chronic diarrhoea or malabsorption may increase to 40%, depending on the irradiated small bowel volume. Late small bowel complications are generally irreversible due to vascular aetiology. Prevention of these complications can be achieved by limiting the volume of small bowel treated. Consequences for radiotherapeutic techniques in treatment for rectal cancer are multiple beam set-up, customised blocking based on visualisation of the small bowel in the treatment position, and the use of a special open table-top device that results in a small bowel shift from the treatment field.

Relationship of acute gastrointestinal toxicity and the volume of irradiated small bowel in patients receiving combined modality therapy for rectal cancer.

To determine the relationship between acute gastrointestinal (GI) toxicity during the combined modality segment and the volume of small bowel in the pelvic radiation field in patients who receive either preoperative or postoperative therapy for rectal cancer. The patient population was derived from four consecutive phase I dose-escalation trials. Combined modality therapy included fluorouracil (5-FU), leucovorin ([LV] bolus daily x 5, days 1 and 29), and pelvic radiation. Twenty patients who received postoperative therapy had a larger volume of small bowel in the pelvic radiation field as compared with 60 who received preoperative therapy (462 +/- 129 v 212 +/- 44 cm3, P = .002). The most significant relationship between acute GI toxicity and volume of small bowel was seen in 12 patients who were treated on the preoperative sequential low-dose LV trial, all of whom received the maximum-tolerated dose (MTD) of 5-FU. The volume of small bowel in patients who experienced grade 3+ toxicity was 731 +/- 274 cm3, as compared with 145 +/- 58 in those who experienced grade 0 to 2 toxicity (P = .005). Likewise, logistic regression analysis showed that 26 patients who received the MTD of 5-FU had the most significant association between GI toxicity and volume of small bowel (P = .036). Our data suggest that the volume of small bowel in the pelvic radiation field may be dose-limiting in the delivery of high-dose 5-FU when combined with LV and radiation therapy.

Measurement of irradiated small bowel volume in pelvic irradiation and the effect of a bellyboard

From June 1992 to January 1993, 51 consecutive patients with pelvic cancers treated with radiotherapy alone, or surgery plus post-operative radiotherapy, were included in a study of the effectiveness of a false table-top (bellyboard) in displacing small bowel loops out of anteriorposterior (AP) and posterioranterior (PA) opposing pelvic fields. The small bowel was opacified with barium. The volume of small bowel within the radiotherapy fields in the prone position with a bellyboard was reduced by 134–300 ml (29%–61%) when compared with that in supine position, and by 136–216 ml (28%–50%) when compared with that in prone position without a bellyboard, depending on the type of previous surgical procedures. The differences were highly statistically significant and likely to be clinically significant. The bellyboard we used is simple, economical, convenient and well tolerated. Its use is recommended, especially when AP and PA pelvic fields are used.

The volume effect in radiation-related late small bowel complications: results of a clinical study of the EORTC Radiotherapy Cooperative Group in patients treated for rectal carcinoma

Purpose: The purpose of this study was to quantify the correlation between irradiated small bowel volume and late occurring small bowel complications. Methods: Small bowel volumes in the high-dose region were measured using orthogonal barium films for 203 patients treated for rectal carcinoma with pelvic postoperative radiotherapy to 50 Gy in an EORTC multicentric study. Results: The 5-year estimate of late pelvic small bowel obstruction requiring surgery was 11%. No correlation between the irradiated small bowel volume and obstruction was detected. The actuarial 5-year estimate of chronic diarrhea varied from 31% in patients with irradiated small bowel volumes below 77 cm 3 to 42% in patients with volumes over 328 cm 3. This correlation was significant in the univariate and multivariate analysis ( p = 0.025). The type of rectal surgery significantly influenced the incidence of chronic diarrhea and malabsorption, the actuarial 5-year estimate being 49% and 26% after low anterior resection and abdominoperineal resection, respectively ( p = 0.04). Conclusions: This study demonstrated that there is a volume-effect in radiation-induced diarrhea at a dose of 50 Gy in 25 fractions. No volume-effect for small bowel obstruction was detected at this dose-level in pelvic postoperative radiotherapy. A review of the literature data on small bowel obstruction indicates that the volume effect at this dose level can only be demonstrated in patients who were treated with extended field radiotherapy (estimated small bowel volume 800 cm 3) after intra-abdominal surgery.

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 cm 3 (median 0 cm 3, range 0–297 cm 3), whereas the corresponding volume was 239 cm 3 (median 181 cm 3, range 0–943 cm 3) 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.

Dose-volume correlation in radiation-related late small-bowel complications: a clinical study

The effects of the volume of irradiated small bowel on late small-bowel tolerance was studied, taking into account the equivalent total dose and type of pre-irradiation surgical procedure. A method was developed to estimate small-bowel volumes in the high-dose region of the radiation treatment using CT-scans in the treatment position. Using this method small-bowel volumes were measured for three-field and AP-PA pelvic treatments (165 cm 3 and 400 cm 3, respectively), extended AP-PA pelvic treatment (790 cm 3), AP-PA treatment of para-aortic nodes (550 cm 3) and AP-PA treatment of para-aortic and iliac nodes (1000 cm 3). In a retrospective study of 111 patients irradiated after surgery for rectal or recto-sigmoid cancer to a dose of 45–50 Gy in 5 weeks, extended AP-PA pelvic treatment ( n = 27) resulted in a high incidence of severe small-bowel complications (37%), whereas for limited (three-field) pelvic treatment ( n = 84) the complication rate was 6%. These complication data together with data from the literature on postoperative radiation-related small-bowel complications were analysed using the maximum like-lihood method to fit the data to the logistic form of the dose-response relation, taking the volume effect into account by a power law. The analysis indicated that the incidence of radiation-related small-bowel complications was higher after rectal surgery than after other types of surgery, which might be explaied by the development of more adhesions. For both types of surgery a volume exponent of the power-law of 0.26 ± 0.05 was established. This means that if the small-bowel volume is increased by a factor of 2, the total dose has to be reduced by 17% for the same incidence of small-bowel complications.

A prospective study of treatment techniques to minimize the volume of pelvic small bowel with reduction of acute and late effects associated with pelvic irradiation

The volume, distribution, and mobility of opacified pelvic small bowel (PSB) were determined by fluoroscopy and orthogonal radiographs in 150 consecutive patients undergoing pelvic irradiation. Various techniques including uteropexy, omental transposition, bladder distention, inclining the patient, and anterior abdominal wall compression in the supine and prone treatment position were studied for their effect on the volume and location of small bowel within the pelvis. Abdominal wall compression in the prone position combined with bladder distention was selected for further investigation because of its simplicity, reproducibility, patient comfort, and ability to displace the small bowel. Factors correlating with the volume of pelvic small bowel (PSB) included prior pelvic surgery, pelvic irradiation (XRT), and body mass index. After pelvic surgery, especially following abdominoperineal resection (APR), there was a greater volume of PSB which was also less mobile. The severity of acute gastrointestinal effects positively correlated with the volume of irradiated small bowel. Overall, 67% of patients experienced little or no diarrhea, 30% developed mild diarrhea, and no patient required treatment interruption. Late gastrointestinal effects correlated with the prior pelvic surgery and with the volume of small bowel receiving greater than 45 Gy. Small bowel obstruction was not observed in 75 patients who had no previous pelvic surgery. However, following pelvic surgery excluding APR, 2/50 patients and following APR, 3/25 patients developed small bowel obstruction.