MRI identifies rectal cancer patients suitable for primary surgery

By Will Boggs MD

NEW YORK (Reuters Health) - 23/4/2019

Current guidelines for the treatment of stage II and III rectal cancer recommend preoperative chemoradiotherapy (CRT) followed by surgery, yet the number of patients needed to treat with CRT to avoid one local recurrence has increased markedly.

Dr. Erin D. Kennedy from Mount Sinai Hospital, in Toronto, Canada, and colleagues at 12 high-volume colorectal-surgery centers across Canada evaluated the use of MRI criteria to identify patients with "good prognosis" rectal tumors for primary surgery.

The good-prognosis criteria included: 1) predicted circumferential resection margin (CRM) greater than 1 mm from the primary tumor, discontinuous tumor nodule, or suspicious lymph node; 2) T category of definite T2, T2/early T3, or definite T3 with less than 5 mm of extramural depth of invasion (EMD); and 3) absent or equivocal extramural venous invasion (EMVI).

All 82 patients recruited for the study underwent primary surgery after meeting these criteria.

Pathologic assessments graded the total mesorectal rectal excision (TME) as complete or near-complete in 98%, with a mean CRM distance of 12.8 mm, the researchers report in JAMA Oncology, online April 11.

Four patients had a positive CRM, for a positive-CRM rate of 4.9%.

Mesorectal lymph nodes were positive in 24 cases (29%), and EMVI was present in 13 cases (16%).

On final pathology, 59% of tumors had stage II or III disease. MRI had understaged 10 cases (12%) and overstaged 16 cases (20%).

After surgery, six patients received postoperative CRT and adjuvant chemotherapy, and 19 patients received adjuvant chemotherapy. Among the 48 patients with stage II or III tumors, 42 (88%) received no form of radiotherapy.

"These findings suggest that CRT may not be necessary for all patients with stage II and III rectal cancer," the researchers conclude. "Further data will be required before this approach can be widely adopted into clinical practice."

"These results should not be extrapolated to patients with higher-risk disease, and the outcomes of the 30% to 40% of patients found to have higher-risk pathologic characteristics with further follow-up will be essential to assess the wisdom of the surgery-first approach," write Dr. Philip B. Paty and colleagues from Memorial Sloan Kettering Cancer Center, in New York City, in an accompanying editorial.

"We agree with the authors that more data are needed, and efforts should continue to focus on selecting patients who do not need chemoradiation therapy and other ways to reduce the overall morbidity of treatment in patients with rectal cancer, such as nonoperative management strategies," they conclude.

Dr. In Ja Park of the University of Ulsan College of Medicine and Asan Medical Center, in Seoul, who has studied the use of neoadjuvant CRT for rectal cancer and was not involved in the research, told Reuters Health by email, "I think this study confirmed previous study results using MRI for patient selection as short-term pathologic results."

However, Dr. Park said, further study is needed focusing on tumor biology and treatment strategies based on tumor responsiveness to neoadjuvant chemoradiotherapy.

Dr. Wolfgang B. Gaertner of the University of Minnesota, in Minneapolis, who studies rectal-cancer treatment, said, "MR should be the imaging modality of choice in newly diagnosed rectal-cancer patients. Selected patients with stage II and perhaps stage III rectal cancer who want to avoid the long-term functional issues associated with neo-CRT can go straight to surgery with a low incidence of positive margins."

"However," he told Reuters Health by email, "we still do not know the long-term oncologic outcomes in patients who go straight to surgery and are found to have positive lymph nodes even when an R0 resection and good-quality TME are performed."

"Surgeons should not go 'all in' on this in patients with stage II given the lack of long-term oncologic outcomes from this study," said Dr. Gaertner, who also was not involved in the study. Dr. Kennedy did not respond to a request for comments.


JAMA Oncol 2019.

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