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Treatment toxicity
Source: Rectal Cancer Treatment (PDQ®)–Health Professional Version, National Cancer Institute.
Source updated: February 12, 2025 · Captured 2026-09-09.
Selected source text with whitespace normalised. This Triangle page is not an NCI PDQ summary. Independent clinical review is pending.
Context: Treatment Option Overview for Rectal Cancer / Chemoradiation Therapy
The acute side effects of pelvic radiation therapy for rectal cancer are mainly the result of gastrointestinal toxicity, are self-limiting, and usually resolve within 4 to 6 weeks of completing treatment.
Of greater concern is the potential for late morbidity after rectal cancer treatment. Patients who undergo aggressive surgical procedures for rectal cancer can have chronic symptoms, particularly if there is impairment of the anal sphincter.[40] Patients treated with radiation therapy appear to have increased chronic bowel dysfunction, anorectal sphincter dysfunction (if the sphincter was surgically preserved), and sexual dysfunction than do patients who undergo surgical resection alone.[28,41-46]
An analysis of patients treated with postoperative chemotherapy and radiation therapy suggests that these patients may have more chronic bowel dysfunction than do patients who undergo surgical resection alone.[47] A Cochrane review highlights the risks of increased surgical morbidity as well as late rectal and sexual function in association with radiation therapy.[40]
Improved radiation therapy planning and techniques may minimize these acute and late treatment-related complications. These techniques include:[48-52]
The use of high-energy radiation machines.
The use of multiple pelvic radiation fields.
Prone patient positioning.
Customized patient molds (belly boards) to exclude as much small bowel as possible from the radiation fields and immobilize patients during treatment.
Bladder distention during radiation therapy to exclude as much small bowel as possible from the radiation fields.
Visualization of the small bowel through oral contrast during treatment planning so that, when possible, the small bowel can be excluded from the radiation field.
The use of 3-dimensional or other advanced radiation planning techniques.
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Preserved source evidence · Independent clinical review pending · Not medical advice