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Can Post-Treatment MRI Features Predict Pathological Circumferential Resection Margin (pCRM) Involvement in Low
A Patra1,2, A D Baheti1,2, S K Ankathi1,2
1Department of Radiodiagnosis, Tata Memorial Hospital, Mumbai, India.
Indian Journal of Surgical Oncology
|December 7, 2020
Summary
Magnetic resonance imaging (MRI) can predict pathological CRM outcomes in rectal cancer patients after neoadjuvant chemoradiation. Unsafe mrCRM on MRI is the only significant predictor of positive pathological CRM, with a high negative predictive value.
Area of Science:
- Oncology
- Radiology
- Gastroenterology
Background:
- The MERCURY II study identified MRI-based risk factors for predicting pathological CRM (pCRM) in lower rectal tumors.
- Applicability of these findings in a homogeneous cohort receiving neoadjuvant chemoradiation (NACTRT) is crucial for treatment planning.
Purpose of the Study:
- To evaluate the MERCURY II study's MRI-based predictors in patients with lower rectal cancer who underwent NACTRT followed by surgery.
- To assess the predictive value of MRI findings for pCRM involvement post-NACTRT.
Main Methods:
- Retrospective review of 132 post-NACTRT restaging MRIs for lower rectal cancer patients (2014-2018).
- Radiological assessment included tumor site, extramural venous invasion (EMVI) status, distance from anal verge, and mrCRM positivity.
- Comparison of MRI findings with histopathological pCRM outcomes using Fisher's exact test.
Main Results:
- Only 7% of patients had pCRM involvement; 88% of these were mrCRM positive (p=0.01).
- The positive predictive value for mrCRM positivity was 12.7%, and the negative predictive value was 98.5% (p=0.01).
- Unsafe mrCRM was the sole significant predictor of pCRM positivity; EMVI and tumor location were not significant.
Conclusions:
- Post-NACTRT restaging MRI, specifically mrCRM assessment, is valuable for predicting pCRM involvement in lower rectal cancer.
- A negative mrCRM finding has a high negative predictive value, suggesting it may help identify patients unlikely to have residual CRM involvement.
- Further research may refine MRI criteria to improve prediction accuracy for rectal cancer treatment strategies.
