Can Post-Treatment MRI Features Predict Pathological Circumferential Resection Margin (pCRM) Involvement in Low Rectal T
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ORIGINAL ARTICLE
Can Post-Treatment MRI Features Predict Pathological Circumferential Resection Margin (pCRM) Involvement in Low Rectal Tumors A. Patra 1,2 & A. D. Baheti 1,2 A. Saklani 2,5
&
S. K. Ankathi 1,2 & A. Desouza 2,3 & R. Engineer 2,4 & V. Ostwal 2,5 & A. Ramaswamy 2,5 &
Received: 15 January 2020 / Accepted: 15 September 2020 # Indian Association of Surgical Oncology 2020
Abstract The MERCURY II study demonstrated the use of MRI-based risk factors such as extramural venous invasion (EMVI), tumor location, and circumferential resection margin (CRM) involvement to preoperatively predict pCRM (pathological CRM) outcomes for lower rectal tumors in a mixed group of upfront operated patients and patients who received neoadjuvant treatment. We aim to study the applicability of results of MERCURY II study in a homogeneous cohort of patients who received neoadjuvant chemoradiation (NACTRT) prior to surgery. After Institutional Review Board approval, post NACTRT restaging MRI of 132 patients operated for low rectal cancer between 2014 and 2018 were retrospectively reviewed by two radiologists for site of tumor, EMVI status, distance from anal verge (< 4 or > 4 cm), and mrCRM positivity. Findings were compared with post surgery pCRM outcomes using Fisher’s exact test. Only 9/132(7%) patients showed pCRM involvement on histopathology, 8 of them being CRM positive on MRI (p = 0.01). The positive predictive value (PPV) of mrCRM positive status and pCRM status was 12.7% (95% CI: 9.7–16.5%), while the negative predictive value was 98.5% (95% CI: 91.4–99.8%) (p = 0.01). EMVI positive and anteriorly located tumors showed higher incidence of pCRM positivity but were not found to be significant (15% vs 5.2% and p = 0.13 and 8.6% vs 2.1% and p = 0.28, respectively). Unsafe mrCRM was the only factor significantly associated with pCRM positivity on post neoadjuvant restaging MRI. Tumors less than 4 cm from anal verge, anterior tumor location, and mrEMVI positivity did not show statistically significant results to predict pCRM involvement. Keywords Magnetic resonance imaging (MRI) . Circumferential resection margin (CRM) . Neoadjuvant therapy . Low rectal carcinoma
Introduction
* A. D. Baheti [email protected] 1
Department of Radiodiagnosis, Tata Memorial Hospital, Mumbai, India
2
Department of Radiodiagnosis, Homi Bhabha National Institute, Mumbai, India
3
Department of Surgical Oncology, Tata Memorial Hospital, Mumbai, India
4
Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India
5
Department of Medical Oncology, Tata Memorial Hospital, Mumbai, India
Low rectal cancer accounts for over a third of all rectal cancers [1–3]. Incomplete tumor resection, identified by pathological circumferential resection margin (pCRM) involvement, results in increased local recurrence and poor survival [4]. pCRM has been detected in 20–36% of lower rectal cancers, which is significantly worse than resection outcomes for upper rectal cancers [1, 2, 5]. This is due to the close relationship with adjacent stru
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