Intra- and interobserver agreement of rectal cancer staging with MRI

Abstract

Background Reliable preoperative staging of rectal cancers is crucial for treatment decision making. Purpose To assess the intra- and inter-observer agreement of rectal cancer staging, including the sub-categories, with magnetic resonance imaging (MRI). Material and Methods The study includes 85 patients (35.3% women; mean age = 62.2 ± 11.2 years) who underwent MRI for rectal cancer staging between August 2020 and April 2021. All the stored images were evaluated independently by two radiologists with 10–15 years of experience. For intra-observer agreement, the evaluations were done two months apart. Analyses were made using kappa, prevalence and bias-adjusted kappa (PABAK), and intraclass correlation coefficient (ICC), where appropriate. Results There was a substantial inter-observer agreement for tumor localization (kappa = 0.665, PABAK = 0.682), mesorectal fascia invasion (kappa = 0.663, PABAK = 0.822), internal and external sphincter involvement (kappa 0.804 and 0.751, PABAK 0.859 and 0.929, respectively), and moderate to substantial agreement for M-staging (kappa = 0.451, PABAK = 0.742) and extramural vascular invasion (kappa = 0.569, PABAK = 0.741). There was also a good inter-observer agreement for T staging and N staging (ICC = 0.862, 95% confidence interval [CI] = 0.788–0.911; and ICC = 0.841, 95% CI = 0.595–0.922, respectively). As expected, intra-observer agreement was better than inter-observer agreement. Conclusion Intra- and inter-observer agreement for MRI staging of rectal cancers using the structured reporting template is good.

Impact of the new rectal cancer definition on multimodality treatment and interhospital variability: Results from a nationwide cross‐sectional study

“…In the current study it was attempted to limit the impact of interobserver variability as much as possible by training all the reviewing clinicians and proctoring the first MRI evaluations [18]. Interobserver variability cannot be ruled out completely and is also present in other diagnostic assessments in clinical practice, such as clinical staging and assessment of other radiological landmarks such as mrEMVI [35, 36]. Nevertheless, this study indicates that implementing the STO as a landmark to define rectal cancer has the potential to reduce interhospital variability, which will result in more standardized care with better comparability of outcomes between hospitals, for which accompanying training is essential.…”