Lymph nodes in MRI-based early-stage rectal cancer: can MRI accurately predict lymph node involvement?

objectivesTo investigate whether quantitative DWI and qualitative T2WI parameters can predict lymph node involvement in clinical early rectal cancer. MATERIALS AND

methodsThis retrospective study included consecutive patients who had rectal MRI from January 1, 2010, to March 31, 2021, showing T1-T2 rectal cancer before undergoing total mesorectal excision without neoadjuvant therapy. Visible mesorectal lymph nodes on DWI were segmented by a junior reader, and ADC values were extracted. Additionally, the junior reader and a senior reader independently recorded qualitative T2WI parameters of the most suspicious lymph node per patient. Histopathology was the reference standard for malignant (pN+) and benign (pN-) lymph node status.

resultsOf 69 patients (37 men and 32 women) (median age, 55 years; IQR: 48-66), 23 (33%) had pN+ status; 46 (67%) had pN- status. ADC

conclusionsAdditional research on alternative and more objective methods for lymph node characterization is needed. KEY POINTS: Question The performance of MRI for nodal staging in clinical early rectal cancer in particular is a knowledge gap in the literature. Findings The Dutch criteria, based on T2WI size and morphologic parameters, performed better in differentiating metastatic from benign lymph nodes than the quantitative DWI ADC parameter. Clinical relevance Accurate nodal staging in early rectal cancer is crucial for treatment decision-making. Our study highlights the need for additional research on alternative and more objective methods for lymph node characterization.