Endorectal Ultrasound Versus MRI for Lower and Middle Rectal Cancer Staging in Upfront Surgery: A Comparative Study

Area of Science:

• Gastroenterology
• Oncology
• Radiology

Background:

• Accurate staging of lower and middle rectal cancer is crucial for treatment planning.
• Neoadjuvant therapy is common, but surgery-first approaches require reliable pre-operative staging.
• Endorectal ultrasound (ERUS) and magnetic resonance imaging (MRI) are key imaging modalities for rectal cancer staging.

Purpose of the Study:

• To compare the accuracy of endorectal ultrasound (ERUS) and magnetic resonance imaging (MRI) in TN staging of lower and middle rectal cancer.
• To evaluate the concordance of ERUS and MRI staging with final pathologic staging in patients treated with surgery first.

Main Methods:

• Retrospective analysis of 101 patients with lower/middle rectal cancer who underwent surgery-first treatment between 2011 and 2022.
• Comparison of diagnostic imaging results (ERUS and MRI) with definitive pathological examination.
• Statistical analysis using Cohen's kappa (κ) coefficient to assess concordance for T and N staging.

Main Results:

• ERUS showed moderate concordance with pathology for T-stage (κ = 0.534), superior to MRI (κ = 0.294).
• ERUS demonstrated fairer concordance for N-stage (κ = 0.337) compared to MRI (κ = 0.138).
• Agreement between ERUS and MRI was moderate for T-stage (κ = 0.410) and fair for N-stage (κ = 0.237).

Conclusions:

• Both MRI and ERUS demonstrate comparable TN staging capabilities in rectal cancer patients not receiving neoadjuvant therapy.
• ERUS presents a valuable alternative for staging rectal cancer when MRI is contraindicated or unavailable.