Patients with rectal cancer considered low risk with tumor-free mesorectal fascia (mrMRF), as indicated on MRI, may be able to forego neoadjuvant chemoradiotherapy (nCRT) and be treated with surgery alone, according to Reinhard Ruppert, MD.
For patients with clinical stage II/III rectal cancer, most guidelines recommend nCRT to lower the risk for locoregional recurrence, noted Dr. Ruppert and colleagues. However, findings from the OCUM (Optimierte Chirurgie Und MRT) study “support the avoidance of nCRT in low-risk patients and suggest that in high-risk patients, neoadjuvant therapy should be intensified to improve prognosis,” the authors wrote in the Journal of Clinical Oncology.
80.4% of Patients Were Treated According to Protocol
The study team conducted a prospective multicenter intervention of patients with rectal cancer (n=1,099; cT2-4, any cN, cM0). Patients were categorized according to suspicious lymph nodes, the minimal distance between the tumor, or tumor deposits, and mrMRF. Those patients with a distance greater than 1 mm had up-front total mesorectal excision (TME; low-risk group), while those with a distance of 1 mm or less or cT4 and cT3 tumors, or both, in the lower rectal third underwent nCRT followed by TME surgery (high-risk group). A 5-year locoregional recurrence rate was the primary endpoint.
Of total patients, 80.4% were treated according to protocol; 40% had nCRT followed by surgery, and 60% underwent upfront surgery. The researchers used Kaplan-Meier analyses, which showed 5-year locoregional recurrence rates of 5.7% (95% CI, 3.2%-8.2%) after nCRT followed by surgery, 2.9% (95% CI, 1.3%-4.5%) after upfront surgery, and 4.1% (95% CI, 2.7%- 5.5%) for patients treated per protocol. For distant metastases, the 5-year rate was 15.9% (95% CI, 12.6%-19.2%) and 30.5% (95% CI, 25.4%- 35.6%), respectively (Table).
A total of 45.1% of a subgroup analysis of 570 patients with lower and middle rectal third c2 and c3 tumors were at low risk. In this group, the 5-year locoregional recurrence rate was 3.8% (95% CI, 1.4%-6.2%) after upfront surgery. In 271 patients considered high risk (involved mrMRF or cT4, or both), the 5-year rate for locoregional recurrence was 5.9% (95% CI, 3.0%-8.8%) and of metastases 34.5% (95% CI, 28.6%-40.4%). Overall survival and disease-free survival were the worst in this group.
5-Year Overall Rate of Locoregional Recurrence Was Less Than 5%
“In approximately half of patients with advanced rectal cancer, nCRT was omitted because of tumor-free mrMRF,” Dr. Ruppert and colleagues wrote. “The 5-year overall rate of locoregional recurrence was less than 5%.” The researchers also observed that patients with mrMRF or cT4 tumors, or both, who underwent surgery following nCRT treatment had a somewhat higher locoregional recurrence rate but the highest rate of distant metastases and the worst prognosis. This study suggests that “patients with localized rectal cancer [who] are classified as low risk based on MRI characteristics can forego neoadjuvant chemoradiation with an acceptably low risk of local relapse,” the study authors noted.