MRI restaging of rectal cancer: The RAC (Response-Anal canal-CRM) analysis joint consensus guidelines of the GRERCAR and GRECCAR groups

Rectal MR Imaging

MR imaging comprising high-resolution T2-weighted imaging and high b value diffusion-weighted imaging has proven effective in guiding treatment selection and preoperative planning for rectal cancer. In addition to staging, it enables the noninvasive assessment of key bioimaging markers such as extramural vascular invasion, tumor deposits, and the presence and location of mesorectal fascia and anal sphincter involvement. After neoadjuvant therapy, MR imaging offers noninvasive treatment response, complementing endoscopic and digital rectal evaluations. This assessment plays a crucial role in determining the feasibility of organ preservation or watch-and-wait strategy in patients who achieve complete clinical response.

Risk of distant metastasis after local excision for near-complete response versus salvage surgery for local regrowth in rectal cancer: Results from an international registry

AIM

Watch and Wait (WW) strategy is currently used for mid/low rectal adenocarcinoma after neoadjuvant treatment (NAT). Local regrowth (LR) is a well-known risk, but its impact on distant metastasis (DM) is increasingly debated. This study aimed to assess the rate of DM after local excision (LE) for near-complete clinical response (ncCR) at restaging versus salvage surgery for regrowth following WW.

METHOD

Retrospective analysis of DM rates from a prospective international registry, comparing patients with ncCR after NAT who underwent LE and patients with initial complete clinical response (cCR) and WW strategy, who underwent salvage surgery for regrowth. The primary endpoint was the 5-year distant metastasis-free survival (5y-DMFS). Univariate/Multivariate analysis were performed to identify risk factors of DM.

RESULTS

Among 138 patients included, 59 had LE for ncCR and 79 had salvage surgery after regrowth including TME (n = 23), APR (n = 30) and LE (n = 26). The 5y-DMFS was lower in patients with surgery at regrowth, 71 % vs. 93 % (p = 0.006). LR was the only independent risk factor associated with DM (OR:3.89; 95 % CI:1.34-11.25; p = 0.012). When only patients managed by salvage LE for LR are considered, 5y-DMFS was equivalent to LE at restaging (87 vs. 93; p = 0.442).

CONCLUSION

Patients with rectal cancer undergoing LE for ncCR after NAT have a significantly lower rate of DM compared to patients undergoing salvage surgery after LR within WW approach. Patients managed by LE for regrowth may represent a distinct subgroup where the risk of subsequent DM is equivalent to patients managed by LE at restage.

MRI of the Rectum: A Decade into DISTANCE, Moving to DISTANCED

Over the past decade, advancements in rectal cancer research have reshaped treatment paradigms. Historically, treatment for locally advanced rectal cancer has focused on neoadjuvant long-course chemoradiotherapy, followed by total mesorectal excision. Interest in organ preservation strategies has been strengthened by the introduction of total neoadjuvant therapy with improved rates of complete clinical response. The administration of systemic induction chemotherapy and consolidation chemoradiotherapy in the neoadjuvant setting has introduced a new dimension to the treatment landscape and patients now face a more intricate decision-making process, given the expanded therapeutic options. This complexity underlines the importance of shared decision-making and brings to light the crucial role of radiologists. MRI, especially high-spatial-resolution T2-weighted imaging, is heralded as the reference standard for rectal cancer management because of its exceptional ability to provide staging and prognostic insights. A key evolution in MRI interpretation for rectal cancer is the transition from the DISTANCE mnemonic to the more encompassing DISTANCED-DIS, distal tumor boundary; T, T stage; A, anal sphincter complex; N, nodal status; C, circumferential resection margin; E, extramural venous invasion; D, tumor deposits. This nuanced shift in the mnemonic captures a wider range of diagnostic indicators. It also emphasizes the escalating role of radiologists in steering well-informed decisions in the realm of rectal cancer care.

Advances in MRI-Based Assessment of Rectal Cancer Post-Neoadjuvant Therapy: A Comprehensive Review

Rectal cancer presents significant diagnostic and therapeutic challenges, with neoadjuvant therapy playing a pivotal role in improving resectability and patient outcomes. MRI serves as a critical tool in assessing treatment response. However, differentiating viable tumor tissue from therapy-induced changes on MRI remains a complex task. In this comprehensive review, we explore treatment options for rectal cancer based on resectability status, focusing on the role of MRI in guiding therapeutic decisions. We delve into the nuances of MRI-based evaluation of treatment response following neoadjuvant therapy, paying particular attention to emerging techniques like radiomics. Drawing from our insights based on the literature, we provide essential recommendations for post-neoadjuvant therapy management of rectal cancer, all within the context of MRI-based findings.