Chemoradiotherapy may be unnecessary for certain rectal cancer patients

Rectal cancer patients given a “good prognosis” on MRI may be able to avoid preoperative chemoradiotherapy (CRT), a technique commonly associated with long-term adverse outcomes, according to results a phase II clinical trial published in JAMA Oncology.

“CRT, followed by surgery, is the recommended approach for stage II and III rectal cancer, wrote Erin D. Kennedy, MD, PhD, with Mount Sinai Hospital, Toronto, Ontario, Canada, and colleagues. “While CRT decreases the risk of local recurrence, it does not improve survival and leads to poorer functional outcomes than surgery alone. Therefore, new approaches to better select patients for CRT are important.”

In the single-arm QuickSilver study, Kennedy et al. evaluated preoperative MRI to more accurately select patients to undergo total mesorectal excision (TME). The prospective trial enrolled 82 patients across 12 high-volume surgery centers.

Tumors identified at MRI were given a “good prognosis” if distance to mesorectal fascia was greater than 1 millimeter (mm); definite T2, T2/early T3, definite T3 with less than 5 mm of extramural depth of invasion; and absent or equivocal extramural venous invasion. 

Overall, 4.9% of “positive prognosis” patients had positive circumferential resection margin (CRM) post-surgery and a mean CRM distance of 12.8 mm.

The results from the QuickSilver study are similar to those of two other studies which used MRI to determine if patients were eligible for surgery, the MERCURY and OCUM studies.

“Taken together, the findings of these studies suggest that, in contrast to CRT for all stage II and III rectal tumors, a more selective approach to CRT based on predicted CRM status may also result in excellent oncologic outcomes,” Kennedy and colleagues, wrote.

Additionally, after pathologic review, 29% of patients had positive mesorectal lymph nodes and 16% had equivocal extramural venous invasion. Another 2% had T4 disease.

According to Kennedy and colleagues, more data is needed before clinics widely incorporate the use of MRI criteria to identify patients for primary surgery.

In a related editorial, Philip B. Paty, MD, of Memorial Sloan Kettering Cancer Center, New York, and colleagues noted the study results cannot be applied to patients with higher-risk rectal cancer, but commended the QuickSilver study authors.

“In summary, the QuickSilver study was a well-designed prospective multi-institutional study that demonstrated a low rate of CRM positivity reflecting good selection and high-quality surgery in patients with low-risk disease,” the researchers wrote. “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.”