Rectal Cancer: Assessing Response to Neoadjuvant Therapy

Area of Science:

• Radiology
• Oncology
• Medical Imaging

Background:

• Magnetic Resonance (MR) imaging is essential for evaluating rectal cancer after chemoradiotherapy (CRT).
• Accurate assessment informs treatment planning, including response evaluation, risk stratification, and nodal staging.
• Challenges exist in post-CRT imaging, such as overstaging invasion and nodal restaging.

Purpose of the Study:

• To outline the critical role of MR imaging in post-CRT rectal cancer assessment.
• To highlight key imaging features and challenges for radiologists.
• To recommend structured reporting for improved accuracy.

Main Methods:

• Utilizing T2-weighted and diffusion-weighted MR imaging for complete response assessment.
• Integrating endoscopic findings for comprehensive evaluation.
• Analyzing common pitfalls like overstaging transmural and mesorectal fascia (MRF) invasion.

Main Results:

• T2-weighted and diffusion-weighted MR imaging are optimal for identifying complete response.
• Overstaging of transmural and MRF invasion is common due to residual stranding.
• Nodal restaging remains a significant challenge in post-CRT assessment.

Conclusions:

• MR imaging is indispensable for post-CRT rectal cancer management.
• Structured reporting or checklists are recommended to enhance diagnostic accuracy and consistency.
• Addressing challenges in nodal staging and overstaging is critical for optimal patient care.