Study Finds Questionable Adherence to Guidelines for Rectal MRI

While magnetic resonance imaging (MRI) is reportedly a key factor in preoperative staging and adjunctive radiochemotherapy for rectal cancer, a new study suggests there is suboptimal adherence to guidelines for rectal MRI acquisition and reporting.

For the retrospective study, recently published by Bulletin du Cancer, researchers reviewed data from rectal MRIs obtained for 69 patients between January 2010 to December 2014 and 73 patients between January 2018 and December 2020. All patients in the two cohorts had locally advanced rectal cancer, according to the study.

For the first study period, looking at adherence to criteria from the 2007 Magnetic Resonance Imaging and Rectal Cancer European Equivalence (MERCURY) study and 2012 guidelines from the European Society of Gastrointestinal and Abdominal Radiology (ESGAR), the study authors found that 58 percent (40/69) of the rectal MRI exams completely adhered to the guidelines.

For the second study period, looking at adherence to 2016 ESGAR guidelines and 2017 guidelines from the Society of Abdominal Radiology (SAR), researchers found that 39.7 percent (29/73) of rectal MRI exams followed all of the recommended criteria.

“If we compare the MRI protocols used between 2018 and 2020 to those used between 2010 and 2014, they are less in line with guidelines (6.8% for the 2016 ESGAR recommendations and 39.7% for the 2017 SAR recommendations),” wrote lead study author Alexandre Mayaud, M.D., who is affiliated with the Radiology Department at the Saint-Etienne Teaching Hospital in Saint-Etienne, France, and colleagues.

The researchers pointed out that obtaining T2-weighted sequences in three planes and adhering to recommended slice thickness (< 4 mm) improved from 78.3 percent and 85.5 percent of exams, respectively, in the first study period to 93.2 percent and 100 percent (to 2017 SAR guidelines), respectively, in the second study period.

However, the study authors also noted a significant decline in adherence to guideline recommendations for sequences in the tumor axis (76.8 percent in the first study period vs. 58.9 percent in the second study period). The researchers said the emergence of diffusion-weighted imaging (DWI) likely contributed to fewer MRI images being angulated in the tumor axis, but they also noted challenges with DWI MRI acquisition.

“This sequence should be performed perpendicular to the rectal tumor axis like in T2-weighted sequences but, in the MRI we analyzed, it was performed in axial plane only,” noted Mayaud and colleagues. “In addition, when radiologists and radiology technologist(s) realized the rectal tumor axis had to be taken into account, they performed oblique instead of parallel sequences to the long axis of the rectal tumor.”

Three Key Takeaways

Guideline adherence decline. The study reveals a decline in adherence to rectal MRI guidelines over time. During the first study period, 58 percent of exams adhered to 2007 MERCURY and 2012 ESGAR guidelines, while in the second period, adherence dropped to 39.7 percent for 2016 ESGAR and 2017 SAR guidelines. This highlights challenges in maintaining adherence to evolving standards.
Evolution of MRI protocols. A comparison of MRI protocols between 2010-2014 and 2018-2020 indicates a deviation from guidelines, with only 6.8 percent aligning with 2016 ESGAR recommendations and 39.7 percent with 2017 SAR recommendations in the later period. The study emphasizes the need for ongoing efforts to ensure that MRI protocols align with current guidelines for rectal cancer evaluation.
Reporting gaps persist. Despite improvements, reporting gaps persist with one example being reporting of mesorectal fascia (MRF) involvement. While reporting increased from 40 percent to 69.2 percent between study periods, the study underscores the ongoing challenge of insufficiently documenting the distance between the tumor and MRF—a crucial prognostic factor. Standardized reporting through MRI templates is advocated to enhance communication and decision-making in patient care.

For distal tumors, the study authors noted low guideline adherence for coronal sequences angulated in the anal canal axis that has worsened in recent years (26.3 percent in the first study period vs. 18.2 percent in the second study period.

The study authors also cited reporting omissions for rectal MRI exams. In regard to mesorectal fascia (MRF) involvement, 40 percent of reports for rectal MRI exams in the first study period noted the distance between the tumor and MRF and 69.2 percent of reports addressed this distance in the second study period.

“Despite a better reporting (29.2%) between the 2 (study) periods, the distance remains insufficiently reported although it is a major prognostic factor,” maintained Mayaud and colleagues.

In light of the inconsistent MRI sequences and reporting noted during both study periods, the researchers emphasized the value of standardized reporting for rectal MRI exams.

“An MRI report template should be used routinely as it enables medical oncologists and surgeons to easily have access to the information they need to make appropriate treatment decisions,” added Mayaud and colleagues. “Moreover, it is a quick and complete reporting tool for radiologists.”