title: Reduced acute bowel toxicity in patients treated with intensity-modulated radiotherapy for rectal cancer.
abstract: OBJECTIVE
  We have previously shown that intensity-modulated radiotherapy (IMRT) can reduce dose to small bowel, bladder, and bone marrow compared with three-field conventional radiotherapy (CRT) technique in the treatment of rectal cancer. The purpose of this study was to review our experience using IMRT to treat rectal cancer and report patient clinical outcomes.
  
  
  METHODS
  A retrospective review was conducted of patients with rectal cancer who were treated at Mayo Clinic Arizona with pelvic radiotherapy (RT). Data regarding patient and tumor characteristics, treatment, acute toxicity according to the Common Terminology Criteria for Adverse Events v 3.0, tumor response, and perioperative morbidity were collected.
  
  
  RESULTS
  From 2004 to August 2009, 92 consecutive patients were treated. Sixty-one (66%) patients were treated with CRT, and 31 (34%) patients were treated with IMRT. All but 2 patients received concurrent chemotherapy. There was no significant difference in median dose (50.4 Gy, CRT; 50 Gy, IMRT), preoperative vs. postoperative treatment, type of concurrent chemotherapy, or history of previous pelvic RT between the CRT and IMRT patient groups. Patients who received IMRT had significantly less gastrointestinal (GI) toxicity. Sixty-two percent of patients undergoing CRT experienced ≥Grade 2 acute GI side effects, compared with 32% among IMRT patients (p = 0.006). The reduction in overall GI toxicity was attributable to fewer symptoms from the lower GI tract. Among CRT patients, ≥Grade 2 diarrhea and enteritis was experienced among 48% and 30% of patients, respectively, compared with 23% (p = 0.02) and 10% (p = 0.015) among IMRT patients. There was no significant difference in hematologic or genitourinary acute toxicity between groups. In addition, pathologic complete response rates and postoperative morbidity between treatment groups did not differ significantly.
  
  
  CONCLUSIONS
  In the management of rectal cancer, IMRT is associated with a clinically significant reduction in lower GI toxicity compared with CRT. Further study is needed to evaluate differences in late toxicity and long-term efficacy.
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Scottsdale, AZ, USA.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Samuelian
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Callister
authors.forename: Jonathan B
authors.initials: JB
authors.lastname: Ashman
authors.forename: Tonia M
authors.initials: TM
authors.lastname: Young-Fadok
authors.forename: Mitesh J
authors.initials: MJ
authors.lastname: Borad
authors.forename: Leonard L
authors.initials: LL
authors.lastname: Gunderson
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000532:radiotherapy* / Q000601:surgery; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D059248:Chemoradiotherapy / Q000379:methods; D003967:Diarrhea / Q000209:etiology; D004751:Enteritis / Q000209:etiology; D005260:Female; D006801:Humans; D007422:Intestines / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D057234:Preoperative Period; D011832:Radiation Injuries / Q000150:complications*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects* / Q000379:methods; D012004:Rectal Neoplasms / Q000188:drug therapy / Q000532:radiotherapy* / Q000601:surgery; D012189:Retrospective Studies; D001743:Urinary Bladder / Q000528:radiation effects*