Radiation proctitis refers to injury or damage of the rectum secondary to radiation therapy. It is postulated that almost half of all patients with pelvic malignancies undergo treatment that involves radiation. Due to the improvement in overall survival in patients with cervical, prostate, rectal, and other pelvic cancers, clinicians will encounter increasing numbers of patients experiencing radiation proctitis. Radiation proctitis is divided into acute and chronic, with chronic proctitis occurring greater than six months after initial radiation treatment.
Radiation proctitis occurs as a result of radiation therapy for malignancy to organs in the pelvis, including the prostate, rectum, and reproductive organs. The degree of radiation proctitis is variable, depending on the modality of which the radiation is delivered, as well as its duration and intensity.
It is difficult to assess the true incidence of radiation proctitis. There are several large series that estimate chronic radiation proctitis to be anywhere between 5 and 11%. Almost 90% of patients who go on to experience chronic radiation proctitis will present in the first two years after treatment.
Radiation therapy works by damaging cells through the direct effect of ionizing radiation on DNA, lipids, and proteins. Water makes up the majority of the cell and ionizing radiation results in the creation of oxygen-free radicles. The direct effect of ionizing radiation also disrupts vital cellular proteins and DNA causing cellular necrosis. Early radiation injury causes edema, mucosal hyperemia, and ulceration of the affected tissue.
The epithelium of the bowel is rapidly proliferating, and as such, it is more predisposed to the effects of radiation damage. Chronically, there is intimal proliferation and hyaline thickening of the media of arterioles. Hypertrophy of rectal smooth muscle occurs, which can affect compliance and defecation as the rectum's ability to distend is diminished. This is further worsened by fibrosis of the serosa.
Patients experiencing radiation proctitis may present with malabsorption, perforation, bowel obstruction, bleeding, and stricture formation. They can also present with fistulous disease. If the anal sphincter is directly involved in the radiation field, patients may present with fecal incontinence.
It is important to consider a recurrent malignancy in patients who present several years after their radiation therapy with symptoms of malabsorption, abdominal pain, increased frequency of bowel movements, and bleeding, etc. While these symptoms may be due to radiation proctitis, they may also signify a local recurrence.
In terms of physical examination, a focused abdominal examination should be performed and, most importantly, a digital rectal exam to identify any anorectal stenosis. The examination can be painful and may not be able to be performed in the office setting, in which case an examination under anesthesia is indicated.
The first step after completing a thorough history and physical examination is to perform either rigid sigmoidoscopy or flexible sigmoidoscopy. An experienced colorectal surgeon or gastroenterologist should perform this exam with minimal insufflation as the inflamed bowel is more susceptible to perforation, especially as it becomes fixated. The examination is likely to reveal a friable mucosa with a multitude of changes, including edema, oozing, and ulcerations.
The mucosa may sometimes appear similar to that which is seen in inflammatory bowel disease with pseudopolyp formation. Areas of ulceration may require a biopsy, but this must be done with caution. There are likely to be multiple areas of strictures that can be indistinguishable from recurrent malignancy.
Barium or water-soluble enema studies may also be performed, which can identify strictures, obstruction, shortening, and narrowing of the rectosigmoid area with loss of the normal curvature. It may also demonstrate decreased compliance of the rectum. The pre-sacral space may appear to be increased due to rectal wall thickening.
Formalin (i.e., formaldehyde 4%–10%) has been studied and used to treat chronic radiation proctitis for over 20 years. The advantages of formalin treatment are that it can be utilized in the clinic setting without the need for general anesthesia, and only the need for light sedation. The mechanism of action of formalin is chemical cauterization of the ulcers and telangiectasias, which are the source of bleeding in chronic proctitis. The formalin can be applied with direct application of a gauze which has been soaked in formalin and the direct application of it to the mucosa of the affected areas, usually under direct vision using rigid proctoscopy. The concentration typically used is 4%, although there are papers that have utilized a 10% solution. A study from Poland showed that after the first application, 50% of the patients had complete resolution of their symptoms, and most patients required an average of 2 treatments. The latest clinical consensus guidelines from the American Society of Colon and Rectal Surgery suggest that short-chain fatty acid enemas are not useful in the treatment of chronic radiation proctitis. Over the years, there have been investigations into other treatments, including ozone therapy, mesalamine, and metronidazole. However, no evidence exists to support their efficacy.
Hyperbaric oxygen therapy has reasonable evidence to support its use for radiation proctitis. Several studies have demonstrated that endoscopic argon beam plasma coagulation can reduce bleeding by approximately 79-100%. While endoscopic argon beam plasma coagulation has been proven, other endoscopic treatments such as bipolar electrocoagulation, radio-frequency ablation, and Nd-YAG laser, have not been sufficiently studied.
Surgery is reserved for patients who did not show improvement in their symptoms following the above medical and endoscopic interventions. It is also used for some of the more severe complications which are associated with radiation proctitis, including, strictures which may lead to large bowel obstruction, fistulas, or even perforation. Studies have estimated that only 10% of patients with radiation proctitis will ultimately require an operative intervention. In very severe cases, a proctectomy may be necessary. However, studies have demonstrated that diversion in the form of an ileostomy or colostomy may improve quality of life, and no further surgical procedures may be needed.
Radiation proctitis should be distinguished from other etiologies of infectious and noninfectious dysentery which include:
Prognosis depends on the severity of individual patients' disease. Up to 30% of patients with severe symptoms may have a significant decrease in health-related quality of life. Patients with radiation proctitis are also at risk of developing a secondary malignancy, of which the majority are colon or rectal cancers.
Patients should be educated that eating foods that are high in fiber can soften stools naturally and improve some symptoms. The use of fiber supplements, including psyllium or konsyl, can help improve symptoms. Patients should also attempt to avoid caffeine, smoking, complex sugars, and alcohol as these can worsen diarrhea and lead to worsening pain and bleeding. Patients should also be educated that if the bleeding is excessive or if they experience symptoms of dizziness and weakness, they should seek immediate medical attention.
Individualized treatment plans are likely required depending on the context of the patient, and discussion with at least one colleague or at an interprofessional team setting regarding the management is recommended. Collaboration and shared decision making and communication are key elements for a good outcome. The interprofessional care provided to the patient must use an integrated care pathway combined with an evidence-based approach to planning and evaluation of all joint activities. The earlier signs and symptoms of a complication are identified, the better is the prognosis and outcome.
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