Locally Advanced Rectal Cancer Evaluation by Magnetic Resonance Imaging after Neoadjuvant Therapy on Decision Making: Cancer Center Experience and Literature Review

Purpose: An accurate clinical and radiological staging is the pyramid of treatment decisions in locally advanced rectal cancer (LARC). Guidelines recommended neoadjuvant chemoradiation therapy (CRT) followed by surgical resection for fit patients with LARC. Determining the aggressiveness of intervention while avoiding needless morbidity according to patient risk remains an unmet pre-operative decision-making need. With newer magnetic resonance imaging (MRI) techniques and image acquisition available at our Cancer Center, we seek to retrospectively review the correlation between pre- and post-CRT MRI response to the surgical pathological stage in order to aide multidisciplinary team decision making.

Methods: Our Cancer Center Rectal Cancer Registry between 2011 and 2015 included 57 patients with LARC, 20 completed standard CRT with surgery, and of those 10 had repeated MRI after CRT.

Results: Our retrospective case series revealed that 90% of the patients had a downstage tumor response on surgical specimen compared to radiological evaluation after CRT, and furthermore, all patients who were re-staged with MRI prior to surgery correlated with the gold standard pathological stage (p = 0.02).

Conclusions: Post-CRT MRI could potentially aide decision making to further avoid 20% of patients with a complete pathological response from a morbid surgery, whereas 10% of patients with an upstaged disease state may require a more aggressive neoadjuvant or planned surgical intervention. We concluded that future multidisciplinary oncology care treatment decision making would benefit from a repeat MRI after neoadjuvant CRT of LARC.