[The role of magnetic resonance imaging to select patients for preoperative treatment in rectal cancer].
BACKGROUND
Traditionally, the decision to apply preoperative treatment for rectal cancer patients has been based on the T- and N-category. Recently, the radial distance of the tumor to the circumferential resection margin (CRM) has been identified as an important risk factor for local failure. By magnetic resonance imaging (MRI) this distance can be measured preoperatively with high reliability. Thus, selected groups have started to limit the indication for preoperative therapy to tumors extending to - or growing within 1 mm from - the mesorectal fascia (CRM+).


METHODS
Pros and cons of this selected approach for preoperative treatment and first clinical results are presented. Prerequisites are the availability of modern high-resolution thin-section MRI technology as well as strict quality control of MRI and surgical quality of total mesorectal excision (TME).


RESULTS
By selecting patients with CRM-positive tumors on MRI for preoperative therapy, only approximately 35% patients will require preoperative radiotherapy (RT) or radiochemotherapy (RCT). However, with histopathologic work-up of the resected specimen after primary surgery, the indication for postoperative RCT is given for a rather large percentage of patients, i.e., for pCRM+ (5-10%), intramesorectal or intramural excision (30-40%), pN+ (30-40%). Postoperative RCT, however, is significantly less effective and more toxic than preoperative RCT. A further point of concern is the assertion that patients, in whom a CRM-negative status is achieved by surgery alone, do not benefit from additional RT. Data of the Dutch TME trial and the British MRC (Medical Research Council) CR07 trial, however, suggest the reverse.


CONCLUSIONS
To omit preoperative RT/RCT for CRM-negative tumors on MRI needs to be further investigated in prospective clinical trials. The German guidelines for the treatment of colorectal cancer 2008 continue to indicate preoperative RT/RCT based on the T- and N-category.
Rödel
Claus
C
Klinik für Strahlentherapie und Onkologie, Universität Frankfurt/Main, Frankfurt/Main, Germany. claus.roedel@kgu.de
Sauer
Rolf
R
Fietkau
Rainer
R
D017024:Chemotherapy, Adjuvant; D003131:Combined Modality Therapy; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008207:Lymphatic Metastasis / Q000473:pathology / Q000532:radiotherapy; D008279:Magnetic Resonance Imaging; D020360:Neoadjuvant Therapy; D009364:Neoplasm Recurrence, Local / Q000209:etiology; D009367:Neoplasm Staging; D017410:Practice Guidelines as Topic; D011379:Prognosis; D018714:Radiotherapy, Adjuvant; D016032:Randomized Controlled Trials as Topic; D012004:Rectal Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery*; D012007:Rectum / Q000473:pathology / Q000601:surgery; D012680:Sensitivity and Specificity