Results of a study presented today at the American Society of Radiation Oncology’s (ASTRO’s) 55th Annual Meeting held in Atlanta, September 22-25, 2013 shows that Sulfasalazine (Azulfidine?, Pfizer), a drug commonly prescribed to reduce diarrhea in patients with rectal bleeding and abdominal pain in patients with ulcerative colitis, a condition in which the bowel is inflamed, does not reduce diarrhea in patients receiving radiation therapy for cancers in the pelvic area.[1] The study also found that the medication may be associated with a higher risk of diarrhea than a placebo when used during radiation therapy to the pelvis.

“Patients receiving radiation therapy in the pelvic region can experience diarrhea which is a negative side effect of the therapy,” explained the study’s lead author Robert Miller, M.D., a radiation oncologist at Mayo Clinic, a nonprofit worldwide leader in medical care, research and education. Miller said that in previous trials sulfasalazine, which treats bowel inflammation, had been shown to decrease diarrhea in patients during pelvic radiation therapy.

Previous research had suggested benefit for sulfasalazine, we were very surprised to find that patients receiving sulfasalazine experienced worse diarrhea than those receiving placebo

Clinical trial
Miller led a two-year, randomized, double-blind, placebo-controlled phase III clinical trial through the Alliance for Clinical Trials in Oncology to evaluate the effectiveness of sulfasalazine versus placebo in inflammation of the bowel during pelvic radiation therapy. The trial included 87 patients, with 78 patients evaluated for the primary endpoint, which was maximal severity of diarrhea up to six weeks after therapy, based on commonly accepted criteria. Patients enrolled in this study came from 24 institutions in the United States.


Patients participating in the trial received either 1,000 milligrams of sulfasalazine or placebo orally, twice each day during radiation therapy and for four weeks thereafter. Each week patient completed bowel function questionnaires during therapy, afterward for six weeks and at 12 and 24 months after therapy. Health care providers graded each patient on the maximum severity and the duration of maximum severity of diarrhea, rectal bleeding, abdominal cramping, constipation and tenesmus, the sensation of incomplete defecation.

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Statistically significant
Interim results from the study found a statistically significant excess of grade 3 diarrhea – passing seven or more stools per day – in patients receiving sulfasalazine versus placebo. The study was halted in May 2013 when researchers determined that it was unlikely sulfasalazine would show real benefit.

Previous studies
“While previous research had suggested benefit for sulfasalazine, we were very surprised to find that patients receiving sulfasalazine experienced worse diarrhea than those receiving placebo,” Miller said. “We now know that sulfasalazine will not help patients receiving radiation therapy in the pelvic region avoid diarrhea as a side effect of the therapy.” Miller noted that this study illustrates the need for large, phase III, randomized controlled trials to better understand which drugs and therapies can help mitigate the negative side effects for patients receiving radiation therapy.

For more information:
[1] Azulfidine?, Pfizer U.S. Physician Prescribing Information [PI Sulfasalazine Tablets; USP]

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