[Complete response after neoadjuvant therapy: how certain is radiology?]

Area of Science:

• Oncology
• Radiology
• Gastroenterology

Background:

• Total neoadjuvant therapy (TNT) is revolutionizing rectal cancer treatment, enabling organ preservation in patients with complete clinical response (cCR).
• The rise of watch-and-wait strategies following TNT necessitates precise imaging for cCR determination and surveillance.
• Current imaging standards, primarily MRI, face challenges in definitively excluding residual malignancy, particularly differentiating scar tissue from viable tumor.

Purpose of the Study:

• To evaluate the performance of radiology, specifically MRI, in assessing complete clinical response (cCR) after total neoadjuvant therapy (TNT) for rectal cancer.
• To discuss the limitations of current imaging techniques in differentiating residual tumor from post-treatment changes.
• To explore strategies for improving diagnostic accuracy in the context of watch-and-wait management for rectal cancer.

Main Methods:

• Review of current literature and clinical practices regarding the role of Magnetic Resonance Imaging (MRI) in rectal cancer staging and response assessment.
• Discussion of the diagnostic performance of MRI, including sensitivity, specificity, and negative predictive value (NPV) for detecting residual tumor.
• Exploration of the potential benefits of integrating MRI with endoscopy, endosonography, and clinical parameters for enhanced diagnostic accuracy.

Main Results:

• MRI demonstrates high sensitivity for initial rectal cancer diagnosis and staging but struggles with specificity in excluding residual tumor post-TNT.
• Differentiating residual scar tissue from vital residual tumor remains a significant challenge, with moderate NPV and low specificity.
• Current imaging assessment criteria lack validation in large cohorts and are often subjective.

Conclusions:

• While MRI is essential for rectal cancer assessment, its limitations in identifying complete response after TNT require attention.
• Integrating MRI with endoscopy, endosonography, and clinical data can improve diagnostic accuracy for cCR and surveillance.
• Enhanced multimodal assessment is crucial for timely identification of incomplete response or recurrence, ensuring appropriate treatment escalation without compromising outcomes.