The Study: The NNT crowd, including the MERCURY and OCUM groups, aims to define a group of patients whose tumors have a favorable prognosis after upfront resection. This “low risk” group takes some careful interpretation because it overlaps T2 tumors that typically wouldn’t get neoadjuvant therapy anyway and the more controversial inclusion of advanced T3 and node-positive tumors that would. Here we have results of the Canadian QuickSilver trial (really creative name, guys) evaluating the upfront surgery approach in such a group of patients. Across these NNT trials, the core favorable criterion is >1 mm between gross tumor (including nodes) and the mesorectal fascia. In QuickSilver, the T3 tumors typically had to be in the middle or upper rectum and could only have 5 mm of extramural invasion with no extramural venous invasion. In other words, the majority of these 82 patients had T2 or early T3 tumors in the mid-rectum. At surgery, 12% of patients were under-staged while 20% were over-staged by MRI, and the agreement between imaging and pathology for nodal status was 68%. The primary outcome of positive circumferential margin was just under 5%, which was in agreement with the MERCURY and OCUM data. What does this tell us? Well, it adds support to a general definition of patients who can possibly omit neoadjuvant chemoradiation and go straight to TME with low risk of positive margin, but we still lack survival or recurrence data most importantly on node-positive patients.
Bottom Line: Carefully selected patients with cT2-3 middle and upper rectal tumors > 1 mm from the mesorectal fascia have a < 5% rate of positive circumferential margin with upfront resection. | Kennedy, JAMA Oncol 2019