Use of Saline-Filled Tissue Expanders to Protect the Small Bowel from Radiation
Use of Saline-Filled Tissue Expanders to Protect the Small Bowel from Radiation
The article by Hoffman, Sigurdson, and Eisenberg updates their experience in the use of temporary saline-filled tissue expanders (TEs) for small bowel exclusion. In their initial prospective study of 34 patients with a median time of patient surveillance after TE placement of 18 months, the authors demonstrated that small bowel was displaced from more than 95% of the radiation therapy treatment volume in 70% of 27 evaluable patients and from more than 75% of the treatment volume in 89% of patients.
The authors present prospective study includes 57 patients with primary or recurrent cancers receiving postoperative radiotherapy over the past 7 years who underwent temporary TE placement for small bowel exclusion. Of the 57 patients, 25 received postoperative external-beam radiation therapy, 16 patients underwent interstitial therapy, and 13 patients had both. Eight complications resulting in patient morbidity were noted. Overall complications occurred in 17 instances. The authors conclude from the present study that, in patients not able to have successful small bowel exclusion accomplished by native tissue, saline-filled TEs are the most reliable method for small bowel exclusion.
Late small bowel injury has been reported to occur at an incidence of 5% to 25% with doses in excess of 4,000 to 5,000 cGy.[2,3] Surgical techniques previously reported to be helpful in reducing the volume of small bowel in an irradiated field include the omental sling, permanent Silastic prosthesis placement, retroversion of the uterus, and use of an absorbable polyglycolic acid mesh sling. Treatment techniques used include bladder distention, multifield arrangement (three or four fields), use of small bowel contrast during radiation therapy simulation, customized belly boards, and Trendelenburg positioning.
Several studies have demonstrated a decrease in gastrointestinal morbidity when several of these techniques are employed. The use of small bowel contrast during radiation therapy simulation treatment planning was shown to reduce the incidence of acute radiation therapy side effects from 93% to 77% and chronic complications from 50% to 23%.
In a prospective study of 150 consecutive patients receiving pelvic radiation therapy, researchers from our institution reported that the severity of acute gastrointestinal effects correlated positively with the volume of irradiated small bowel. Late effects correlated with the dose of radiation and volume of the small bowel receiving more than 4,500 cGy.
A Matter of Position
The technique of anterior abdominal compression with bladder distention in the prone position was found to be more effective than the supine position for displacing small bowel from the treatment field. In some patients, especially those who were obese, treatment in the prone position without abdominal compression actually increased the volume of small bowel in the pelvis.
It is our present policy for patients receiving pelvic irradiation at Mercy Hospital to undergo radiation therapy simulation with the use of small bowel contrast, anterior abdominal wall compression, and bladder distention while in the prone position. This strategy has proven to be simple and highly reproducible, while maintaining patient comfort.
Adjuvant radiation therapy for primary or recurrent cancers in the pelvis often requires small bowel exclusion due to:
- treatment of recurrences in previously irradiated patients; and
- treatment of primary cancers that have positive margins or residual disease after surgery, necessitating doses greater than 5,000 cGy.
For these situations, several techniques have been developed. Polyglycolic acid mesh has been shown to undergo complete reabsorption within 3 to 5 months, which would require that adjuvant radiation be initiated within 3 weeks postoperatively. Mesh could be a reasonable option for previously irradiated patients who are undergoing resection for recurrent disease and who are recommended to receive additional radiation at doses in the range of 1,500 to 2,000 cGy (eg, for tumor adherence, positive margins). Mesh could also be considered for patients with primary rectal tumors treated initially with preoperative chemoradiation who require additional postoperative radiation because they are considered to be at high risk of local recurrence.
Intraoperative radiation therapy is an attractive alternative to external-beam radiation in these situations due to the ability of the surgeon and radiation oncologist to displace normal tissues from the intended radiation field, thereby avoiding undue late effects. However, this modality is not available in many institutions.
The authors correctly point out that many patients who receive adjuvant radiation therapy often require adjuvant chemotherapy as well, eg, patients with B2/C rectal carcinoma. Radiation therapy often is not completed for up to 150 days postoperatively in these situations. The use of a mesh in these patients would be infeasible given its reabsorption properties.
The authors describe a technique for using temporary saline-filled TEs in these situations. They point out that the technique is reliable, safe, and easy to use. In 14 patients treated with pelvic radiation therapy who underwent TE placement, Herbert et al demonstrated that placement of the device correlated with decreased small bowel volume within the radiation treatment field, as well as diminished acute gastrointestinal morbidity, when compared with 63 patients who did not receive the expander.
Hoffman, Sigurdson, and Eisenberg correctly point out that their experience included a learning curve in the use of the expanders; this led to a different placement technique, which, in turn, resulted in a reduced incidence of post-withdrawal complications. Overall, this technique is more expensive than other methods due to the cost of the materials, as well as the cost of additional CT, MRI, or small bowel series performed during radiation therapy to check for potential TE deflation.
Recently, a randomized trial has reported, for the first time, improved overall survival with the addition of preoperative irradiation in patients with resectable rectal cancer, as compared with surgery alone. In addition, preoperative chemoradiation has been reported to produce less acute grade 3 to 4 toxicity than postoperative adjuvant therapy. With the increased interest in preoperative chemoradiation for resectable as well as unresectable rectal cancers, there may be a limited need for postoperative small bowel exclusion methods, such as TE placement, in lieu of treatment planning, physical maneuvers, and, possibly, mesh placement.
Patients receiving doses of adjuvant radiation therapy above the level generally considered to be safe for the small bowel who require small bowel exclusion should undergo a surgical procedure utilizing native tissues (eg, omental sling, uterus retroversion) as the initial treatment of choice. However, in patients who cannot undergo these procedures, the placement of a TE device, especially in patients receiving adjuvant chemoradiation, is a reasonable option, when performed by experienced hands, for decreasing the risk of late radiation injury to the bowel. The authors should be commended for their continued investigation into the use of this promising technique.
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