Intra- and Interobserver Variability in Magnetic Resonance Imaging Measurements in Rectal Cancer Patients

SIMPLE SUMMARY: Colorectal cancer is the second most common cancer and was the second most common cause of cancer-related death in Europe in 2018. Accurate lymph node staging in primary rectal cancer staging is essential for the selection of the proper treatment regimen. In 2018, The European Society of Gastrointestinal and Abdominal Radiology published consensus recommendations for primary rectal cancer staging, and suggested that lymph nodes be assessed by size, morphology, and location in- or outside the mesorectal fascia. Our study aimed to assess the inter- and intraobserver variability in size, apparent diffusion coefficient measurements, and morphological characterization among inexperienced and experienced radiologists. Our data indicate that subjective variables like morphological characteristics are less reproducible than numerical variables, regardless of the level of experience of the observers. ABSTRACT: Colorectal cancer is the second most common cancer in Europe, and accurate lymph node staging in rectal cancer patients is essential for the selection of their treatment. MRI lymph node staging is complex, and few studies have been published regarding its reproducibility. This study assesses the inter- and intraobserver variability in lymph node size, apparent diffusion coefficient (ADC) measurements, and morphological characterization among inexperienced and experienced radiologists. Four radiologists with different levels of experience in MRI rectal cancer staging analyzed 36 MRI scans of 36 patients with rectal adenocarcinoma. Inter- and intraobserver variation was calculated using interclass correlation coefficients and Cohens-kappa statistics, respectively. Inter- and intraobserver agreement for the length and width measurements was good to excellent, and for that of ADC it was fair to good. Interobserver agreement for the assessment of irregular border was moderate, heterogeneous signal was fair, round shape was fair to moderate, and extramesorectal lymph node location was moderate to almost perfect. Intraobserver agreement for the assessment of irregular border was fair to substantial, heterogeneous signal was fair to moderate, round shape was fair to moderate, and extramesorectal lymph node location was substantial to almost perfect. Our data indicate that subjective variables such as morphological characteristics are less reproducible than numerical variables, regardless of the level of experience of the observers.