Seven Key Considerations with Rectal Cancer MRI

Recently published statistics from the American Cancer Society (ACS) reveal concerning trends for colorectal cancer with the prevalence of advanced stage disease increasing to 60 percent in 2019.¹ For people under the age of 55, the diagnosis of colorectal cancer has nearly doubled from an 11 percent prevalence in 1995 to 20 percent in 2019, according to the ACS.¹

Given the importance of timely diagnosis and appropriate staging, researchers recently reviewed pertinent principles in magnetic resonance imaging (MRI) assessment of patients with rectal cancer in a cum laude awarded poster presentation at the European Congress of Radiology (ECR) in Vienna, Austria.² Here are a few key takeaways.

1. Emphasizing that mesorectal fascia status is a key risk factor for recurrence of rectal cancer, the poster authors said a positive MRI finding would reveal a tumor lying within 1 mm of the mesorectal fascia. They called the circumferential resection margin for total mesorectum excision (TME) or transanal TME a “holy plane,” defined by the virtual space between the parietal fascia and the mesorectal fascia.²

2. Tumor location below the peritoneal reflection increases risks for peritoneal dissemination and lateral pelvic node involvement, wrote Roberto Garcia-Figueiras, M.D., who is affiliated with the Department of Radiology at the Complejo Hospitalario de Santiago de Compostela in Spain, and colleagues.

3. For recognition and staging of early tumors, the poster authors suggested assessing the submucosal layer between the tumor and the muscularis propria. When using contrast-enhanced MRI, a submucosal enhancing stripe status can help differentiate between stage T2 tumors and stage T1 or lower rectal tumors, according to the study authors.

4. Pointing out a diverse range of prognosis for stage T3 tumors, Garcia-Figueiras and colleagues recommended careful assessment of tumor characteristics and other prognostic factors, but also maintained that tumor spread depth on MRI provides the most reliable prognostic information.

5. Acknowledging the difficulty of differentiating between early stage T3 tumors and stage T2 tumors, the poster authors caution that spiculated desmoplastic reaction in peritumoral inflammation or perirectal fat can mimic tumor involvement.

6. Garcia-Figueiras and colleagues noted that T2-weighted MRI sequences with fat suppression and dynamic contrast-enhanced MRI can be beneficial in diagnosing mucinous tumors, which are associated with advanced tumor presentation, multiple metastatic sites, and young age. On T2-weighted MRI, the presence of mucin pools can lead to high signal intensity similar to or brighter than mesorectal fat.

7. Staging of T4b tumors include tumors that invade or are adherent to bones, muscles, nerves, blood vessels and ureters. This staging does not apply to tumors that invade or are adjacent to the internal anal sphincter, the anterior peritoneal reflection or the intersphincteric space, according to Garcia-Figueiras and colleagues.

References

1. American Cancer Society. American Cancer Society releases new colorectal cancer statistics; rapid shifts to more advanced disease and younger people. Cision PR Newswire. Available at: https://www.prnewswire.com/news-releases/american-cancer-society-releases-new-colorectal-cancer-statistics-rapid-shifts-to-more-advanced-disease-and-younger-people-301759641.html . Published March 1, 2023. Accessed March 3, 2023.

2. Antelo MC, Calvo AN, Gonzalez MB, Gonzalez SB, Garcia-Figueiras R. Common misconceptions about rectal cancer MRI. Poster presented at the European Congress of Radiology, March 1-5, 2023, Vienna, Austria. Available at https://portal.myesr.org/esr/membership/poster/f923bc62-2b51-4de4-876d-7ef029e40baa/show/results#content . Accessed March 3, 2023.