MRI-based guidelines for selective neoadjuvant treatment in rectal cancer: Does MRI adequately predict the indication for radiotherapy in daily practice in a large teaching hospital.

Abstract

OBJECTIVES\nAccording to new Dutch guidelines for rectal cancer, MRI-defined tumour stage determines whether preoperative radiotherapy is indicated. Therefore, we sought to evaluate if preoperative MRI accurately predicts the indication for neoadjuvant treatment in rectal cancer cases in daily practice according to the new Dutch guidelines.\n\n\nMETHODS\nData for all rectal cancer patients who underwent mesorectal excision in our hospital, between January 2011 and January 2018 were collected retrospectively. We compared histopathologic outcome with tumour staging on preoperative MRI for patients who received no radiotherapy prior to resection or short-course radiotherapy directly followed by resection.\n\n\nRESULTS\nOf 223 patients treated according to the old guidelines, 94% received neoadjuvant therapy. Of 301 patients treated according to the new guidelines, only 49% did. Under the old guidelines, MRI predicted lymph node metastases with a sensitivity of 74.2% and a specificity of 52.6%. With the new guidelines, sensitivity was 47.5% and specificity was 77.3%. The new guidelines resulted in 45% more patients not being exposed to disadvantages of radiotherapy, but 13% of all patients were undertreated.\n\n\nCONCLUSIONS\nConcordance between clinical lymph node staging on preoperative MRI and histopathologic staging is limited, resulting in many rectal cancer patients not receiving adequate neoadjuvant therapy.