Primary Surgery Outcomes in MRI-Based ‘Good-Prognosis’ Rectal Cancer


Key Points

  • Positive circumferential resection margins were found in 4.9% of patients after primary surgery.
  • 88% of patients with stage II or III disease did not receive any form of radiotherapy.

In a Canadian phase II trial reported in JAMA Oncology, Kennedy et al found a low rate of positive circumferential resection margins after primary surgery in patients with rectal cancer considered to have a ‘good prognosis’ based on magnetic resonance imaging (MRI) criteria.  

As noted by the investigators, “Chemoradiotherapy, followed by surgery, is the recommended approach for stage II and III rectal cancer. While chemoradiotherapy decreases the risk of local recurrence, it does not improve survival and leads to poorer functional outcomes than surgery alone.”

Study Details

The study included 82 patients newly diagnosed with rectal cancer with an MRI-predicted good prognosis between September 2014 and October 2016 at 12 high-volume colorectal surgery centers in Canada. MRI criteria for good-prognosis tumors consisted of: distance to the mesorectal fascia > 1 mm; definite T2, T2/early T3, or definite T3 with < 5 mm of extramural depth of invasion; and absent or equivocal extramural venous invasion.

The primary outcome measure was positive circumferential resection margin rate. Most patients were male (74%), and the median age at surgery was 66 years.

Positive Circumferential Resection Margin Rate

Based on MRI findings, 65% of tumors were midrectal, 60% were T2/early T3, and 63% had no suspicious lymph nodes. Final pathology showed that 91% of tumors were T2 or greater, 29% were node-positive, and 59% were stage II or III. Positive circumferential resection margins were found in 4 (4.9%) of the 82 patients.

Overall, 25 patients (30%) received adjuvant treatment, with 6 receiving chemoradiotherapy and 19 receiving chemotherapy. Among the 48 patients with stage II or III tumors, 42 (88%) did not receive any form of radiotherapy.

The investigators concluded: “The use of MRI criteria to select patients with good prognosis rectal cancer for primary surgery results in a low rate of positive circumferential resection margins, and suggests that chemoradiotherapy may not be necessary for all patients with stage II and III rectal cancer.”

Erin D. Kennedy, MD, PhD, of the Department of Surgery, Mount Sinai Hospital, Toronto, is the corresponding author for the JAMA Oncology article.

Disclosure: The study was supported by the Mount Sinai Hospital-University Health Network Academic Medical Organization Innovation Fund. For full disclosures of the study authors, visit

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