Determinants of magnetic resonance imaging overstaging in rectal cancer T-staging

Abstract

BACKGROUND

The front-end of an efficient clinical pathway for rectal cancer is a high-precision local-stage examination that determines the necessity of surgery and whether neoadjuvant therapy should be given. Currently, in cancer treatment, according to the extent of tumour spread, a decision will be made among local excision, total mesorectal excision, and neoadjuvant chemoradiotherapy. As management has moved away from a general radical procedure to personalised organ-preserving and neoadjuvant-intensive frameworks, the clinical relevance of this assessment has been increasing. Incorrect staging is related to a high risk of morbidity; that is, an overestimation of the stage may lead to unnecessary toxicity or extensive surgery, and an underestimation of the stage risks failing to treat early and progressing to local recurrence. Therefore, enhancing the predictive accuracy of preoperative T classification needs to be done to improve surgical quality.

AIM

To explore the factors influencing the accuracy of preoperative magnetic resonance imaging (MRI) in rectal cancer T staging, with particular emphasis on factors contributing to MRI overstaging in routine clinical practice.

METHODS

This retrospective single-center study included 349 patients with rectal cancer, including carcinoma in situ, who underwent surgery at Beijing Anzhen Nanchong Hospital, Capital Medical University and Nanchong Central Hospital between January 2020 and December 2023. All patients underwent preoperative MRI-based tumor-node-metastasis staging assessment and had postoperative pathological confirmation. Univariate and multivariable logistic regression analyses were performed to identify factors associated with MRI overstaging. Reader-related variables, including experience, subspecialty background, specialized training, reading duration, blinded reading, and multidisciplinary team participation, were also evaluated.

RESULTS

The overall accuracy of preoperative MRI T staging was 58.5% (204/349), with overstaging in 35.5% (124/349) and understaging in 6.0% (21/349). MRI accuracy by T stage (T1-T4) was 25.0%, 29.4%, 80.6%, and 83.6%, respectively. Multivariate analysis revealed that a relatively small tumor size, neoadjuvant treatment-related regression, and polypoid morphology were independently associated with MRI overstaging. Reader-related analyses revealed that limited experience, a general radiology background, a lack of specialized training, shorter interpretation time, and the absence of multidisciplinary team participation were associated with higher overstaging rates.

CONCLUSION

A new size and shape of the tumour have appeared in the following observations after treatment, so further imaging studies were recommended. Small tumors with a polypoid structure or pronounced post-neoadjuvant regression may be less likely to be overclassified radiographically, thus avoiding overstaging. Add endorectal ultrasonography, standardised reporting forms and cross-disciplinary evaluation to improve the diagnostic accuracy for vulnerable groups.

Keywords: Magnetic resonance imaging; Rectal cancer; T staging; Overstaging; Reader-related factors

Core Tip: Current data indicate a propensity for magnetic resonance imaging to overestimate the T category of rectal tumors, particularly when evaluating diminutive lesions, polypoid morphologies, or cases demonstrating pronounced post-neoadjuvant regression. Diagnostic precision was concurrently compromised by several interpreter variables; restricted clinical tenure, absent structured training, abbreviated review durations, and solitary reading without multidisciplinary team input all exacerbated staging inaccuracies. Consequently, such observations advocate for adopting a risk-stratified clinical paradigm. For these vulnerable scenarios, standard magnetic resonance imaging assessments require augmentation through endorectal ultrasonography alongside cross-specialty panel consensus.