title: Oncological short-term effects and adverse events of MRI-guided selective neoadjuvant radiochemotherapy for rectal cancer.
abstract: OBJECTIVE
  To investigate the oncological short-term effects and acute side-effects of magnetic resonance imaging (MRI)-guided selective neoadjuvant radiochemotherapy (nRCT) for rectal cancer.
  
  
  METHODS
  In a prospective multicenter cohort study of 230 patients with rectal cancer stage II or III, nRCT was applied in the following situations (n=96) only: cT4 tumors, cT3 tumors of the distal rectum or tumors leaving a circumferential resection margin (CRM) of ≤1 mm between the tumor and the mesorectal fascia (mrCRM+). Pre-therapeutical tumor stage and involvement of mesorectal fascia were assessed by MRI and were compared with the pathological findings of the rectal specimens. Furthermore, tumor regression grades, acute side-effects, and surgical complications were analysed.
  
  
  RESULTS
  Using selective nRCT, 62 out of 72 patients (86%) with mrCRM+ had tumor-negative pathological CRM. Reduction of T category was observed in 62% and of N category in 88% of patients. Lymph node metastasis was found by pathology in only 21% of all irradiated patients. Histologically complete tumor regression (ypT0ypN0) was observed in 15% and intermediate regression (more than 25%, but not complete) in 67% of patients. Fifteen percent of patients suffered from grade 3 toxicity, but no grade 4 toxicity occurred. nRCT did not adversely influence surgical morbidity.
  
  
  CONCLUSIONS
  Despite the negative selection of locally advanced rectal cancer cases for nRCT, impressive rates of tumor down-staging and eradication of tumor from the mesorectal fascia were achieved. The rate of complete regression is comparable to that in the literature. Moreover, the selective use of nRCT spared a considerable percentage of patients with stage II/III rectal cancer severe irradiation toxicity.
authors.affiliation: Department of Surgery, Hospital of Liestal, University of Basel, Basel, Switzerland. christoph.maurer@ksli.ch
authors.forename: C A
authors.initials: CA
authors.lastname: Maurer
authors.forename: D
authors.initials: D
authors.lastname: Mattiello
authors.forename: J
authors.initials: J
authors.lastname: Duwe
authors.forename: R
authors.initials: R
authors.lastname: Ruppert
authors.forename: H
authors.initials: H
authors.lastname: Ptok
authors.forename: J
authors.initials: J
authors.lastname: Strassburg
authors.forename: T
authors.initials: T
authors.lastname: Junginger
authors.forename: S
authors.initials: S
authors.lastname: Merkel
authors.forename: P
authors.initials: P
authors.lastname: Hermanek
mesh_terms: D059248:Chemoradiotherapy / Q000009:adverse effects*; D015331:Cohort Studies; D006801:Humans; D008207:Lymphatic Metastasis; D008279:Magnetic Resonance Imaging; D009367:Neoplasm Staging; D011183:Postoperative Complications / Q000453:epidemiology; D011446:Prospective Studies; D061089:Radiotherapy, Image-Guided; D012004:Rectal Neoplasms / Q000473:pathology / Q000628:therapy*; D012086:Reoperation