Tolerability of Radiation Therapy in Patients with Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic idiopathic gastrointestinal (GI) disorder characterized by immunological inflammation with repeated exacerbation and remission. IBD includes ulcerative colitis (UC), Crohn's disease (CD), and indeterminate colitis (IC) [1,2]. IBD is a risk factor for colorectal cancer (CRC) and the morbidity rate increases with time [3]. Furthermore, the prognosis of CRC with IBD is poorer than that in patients without IBD [4,5]. However, the incidence of CRC has decreased due to the improvement of IBD activity by modern management methods, particularly surveillance by regular lower endoscopic examination; surgery; nutritional therapy; and the use of 5-aminosalicylate (5-ASA), steroids, immunosuppressant’s, and anti-tumor necrosis factor alpha (TNFα) agents [4]. Although IBD occurs frequently in Europe and the United States, its incidence is increasing each year in Asian countries including Japan. The incidence rate of UC was reported to be comparable to those in Europe and the United States [6,7]. There were approximately 210,000 patients with IBD in Japan in 2013, the highest number among designated specific intractable diseases and about twice the number of patients reported in 2004 [6]. Around the beginning of the 21st century, several papers reported the potential for radiation therapy (RT) to the abdominal pelvis to cause severe acute and late GI toxicity in patients with IBD [8-10]. However, it was not clear if these toxicities were caused by adverse events due to RT or by the exacerbation of poorly controlled IBD. For this reason, there is no consensus on the safety of RT applied to the abdominal pelvis of patients with IBD. Therefore, the present study examined the frequencies of acute and late GI adverse events of RT in patients with IBD and assessed their impact on IBD activity.