J. J. Blank2, N. G. Berger2, P. M. Knechtges3, R. W. Prost3, C. Y. Peterson1, K. A. Ludwig1, T. J. Ridolfi1 1Medical College Of Wisconsin,General Surgery, Colorectal Division,Milwaukee, WI, USA 2Medical College Of Wisconsin,General Surgery,Milwaukee, WI, USA 3Medical College Of Wisconsin,Radiology,Milwaukee, WI, USA
Introduction: The management of rectal cancer relies heavily on Magnetic Resonance Imaging (MRI) for proper staging. MRI is an invaluable but imperfect tool, with tumor depth being reported incorrectly in up to 1/3 of cases. If tumor depth is wrongly reported as too deep or lymph node status is wrongly reported as positive it will relegate the patient to additional unnecessary radiation and chemotherapy. Additionally, 10%–30% of individuals who undergo preoperative chemoradiation are found to have a complete pathologic response. Some centers are now adopting a ‘‘watch and wait’’ approach, foregoing surgery for high operative risk individuals who have clinical evidence of a complete pathologic response. Resection is still considered standard of care in healthy individuals as no clinically available imaging technology is able to accurately predict complete response. Standard MRI technology currently operates at 3T, a unit of magnetic strength. The Medical College of Wisconsin Center of Imaging Research houses one of only twenty 7T MRIs worldwide. We hypothesize that 7.0 T MRI will accurately predict postoperative tumor depth and nodal status.
Methods: Patients undergoing low anterior resection for rectal cancer were enrolled in the trial. Patients received neoadjuvant treatment based on current NCCN guidelines. Following excision, the surgical specimen was secured in a normal saline filled canister and subsequently imaged in the 7T MRI. A radiologist blinded to the pathologic data interpreted the specimen images for tumor depth and nodal status. Imaging data was then compared to the pathology reports to determine accuracy.
Results: Between July 2015 and July 2016, 5 patients met inclusion criteria. Radiologic and pathologic interpretation of specimen was identical regarding tumor depth in 3 of 5 patients (60%) Additionally, nodal status was correctly predicted by MRI in 3 of 5 patients (60%). One patient had perfect correlation between radiologic interpretation and pathologic specimen.
Conclusion: Discrepancy between the pathologic and radiologic staging of the specimens was identified. This is not unexpected as the current project represents the first images of the human rectum obtained at 7T. We anticipate that 7T MRI radiologic staging will become more accurate as specific imaging characteristics of varying stages of rectal cancer are defined. 7T MRI holds promise in accurately staging rectal cancer and possibly predicting response to neoadjuvant therapy.