Radiation-induced proctitis is a common complication associated with radiation directed to the abdomen and/or pelvis in the treatment of rectal, prostate, or cervical malignancies. The symptoms of proctitis can begin as early as immediately following therapy (acute) or as late as well after completion of radiation therapy (delayed or late). Acute proctitis symptoms can persist up to 3 months, while delayed or late proctitis is a chronic disease that may continue for decades. Proctitis symptoms include rectal bleeding, diarrhea, discharge of mucus and tenesmus, a feeling or inability to empty the bowel upon defecation, which is likely a result of extensive rectal tissue fibrosis or possibly the formation of rectal strictures.
The most common first-line therapies have been adapted from the treatments used in inflammatory bowel disease (IBD), including 5-ASA, steroids, sucralfate and metronidazole. Increasingly, endoscopic therapies are being employed to control bleeding associated with radiation proctitis which includes heat probes, lasers, and most commonly argon plasma coagulation (APC). Unfortunately, current treatment options for radiation proctitis vary as greatly in their rate of success as they do in method.
|Disease is evident at day 3, peaks near day 7 and persists through the final evaluation.||10 days||Endoscopy score, weight, incidence of diarrhea, histology|
|Disease is evident the day after the final dose of radiation. Severity peaks on day 13 and persists through the final evaluation.||28 days||Endoscopy, score, weight, incidence of diarrhea, histology|
Biomodels offers both acute and fractionated rat and mouse models of radiation-induced proctitis. In both models, lead shielding is used to cover the rat except for a 3cm X 4cm area of the low pelvis. This area contains approximately a 2 cm length of the rectum and distal colon in the middle of the field. The peak of disease severity differs between the acute and fractionated models. End points in this model include endoscopic proctitis scores based on a standardized scale that is representative of the clinical assessment, combined with weight, incidence of diarrhea and histological analysis.
Animals receive one acute dose of radiation on Day 0 of the study and then are evaluated daily
for survival, body weight, evidence of bloody stool and diarrhea. On three of those days, animals are anesthetized and examined via video endoscopy to determine proctitis severity.
Animals receive 8 fractionated doses of radiation on days 0, 1, 2, 3, 6, 7, 8, and 9 of the study.
Mean Radiation Induced Proctitis Scores
*Proctitis severity scores resulting from fractionated radiation exposure
Animal models of toxicities caused by anti-neoplastic therapy
Stephen T. Sonis, Gregory Lyng, and Kimberly Pouliot
Tumor Models in Cancer Research, second edition, Beverly A. Teicher editor