Complications
Pelvic toxicity is common during chemoradiation. Critical normal tissues that need to be considered in the treatment of anal canal cancer include bone marrow, rectum, small bowel, bladder, and skin. The acute toxicity is due to a combination of chemotherapy and radiation therapy.
Toxicities include leukopenia, thrombocytopenia, proctitis, diarrhea, cystitis, and acute dermatitis.
It must be emphasized that even when pelvic radiation is delivered with appropriate doses and techniques, almost all patients receiving combined-modality treatment for anal cancer will develop acute grade 3+ toxicity and will require a treatment break at some point in their treatment course.
Intensity-modulated radiation therapy reduces acute gastrointestinal toxicity, compared with conventional radiation therapy. Evening delivery of radiation therapy may reduce acute radiation therapy-related diarrhea, compared with morning delivery.[69] Low-quality evidence suggests that protein supplements, dietary counseling, or probiotics may reduce acute radiation therapy-related diarrhea.[69]
Intensity-modulated radiation therapy probably reduces long-term gastrointestinal toxicity, compared with conventional radiation therapy.[69] Even when appropriate radiation techniques are used, severe long-term toxicity may develop anywhere from 6 to 18 months after therapy in approximately 1% of patients. This can affect any organ in the pelvic radiation field. Femoral head fractures occur in 1% to 3% of patients and are most likely in postmenopausal women.
Although some reports demonstrate that radiation therapy can affect sphincter function and functional results in rectal cancer, they are not directly applicable to anal cancer, because patients do not undergo pelvic surgery. There are limited reports of functional outcome in the anal cancer literature. One series reports that full function was maintained in 93% of patients and a second series that used anorectal manometry reported complete continence in 56%.[70][71] Another reported good-to-excellent function in 93% of patients with a minimum of 1 year of follow-up.[72]
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