Association of Pelvic Structure Involvement and Tumor Morphology at MRI with Prognosis Following Resection in Locally Recurrent Rectal Cancer.

Purpose To determine the influence of location, extent of tissue invasion, and tumor morphology at MRI on the resectability of locally recurrent rectal cancer (LRRC) and postresection oncologic outcomes of LRRC. Materials and Methods This retrospective observational study included consecutive patients diagnosed with LRRC who underwent surgery with curative intent at the Catharina Hospital Eindhoven and Karolinska University Hospital Stockholm between January 2003 and December 2017. Two expert radiologists reviewed available MR images while adhering to a standardized reviewing checklist. The effect of pelvic structure involvement, tumor morphology on the primary outcome of resection margin status, and secondary outcomes of overall survival and disease-free survival were assessed using univariable and multivariable logistic regression and Cox proportional hazard analyses. Results The final analysis included 328 patients with LRRC (mean age ± SD, 64.9 years ± 9.6; 126 female, 202 male). Resection margins were negative in 217 (66.2%) patients and positive in 111 patients (33.8%). Tumor size, tumor type, and border type on MR images were all associated with resectability. Central recurrences were associated with the lowest likelihood of positive resection margins (odds ratio [OR], 0.45; 95% CI: 0.28, 0.71; P < .001), whereas lateral recurrences were associated with the highest likelihood (OR, 2.00; 95% CI: 1.25, 3.19: P = .004). Similarly, central recurrences were associated with better disease-free survival compared with lateral recurrences (hazard ratio [HR], 0.69; 95% CI: 0.53, 0.90; P = .006 vs HR, 1.49; 95% CI: 1.14, 1.94; P = .003, respectively). Similar findings were observed after correcting for resection margin status. Conclusion Standardized MRI assessment of tumor characteristics in patients with LRRC resulted in the identification of specific prognostic factors. Central compartment involvement and well-defined tumors were associated with improved prognosis, whereas lateral compartment involvement and fibrotic spiculated tumors were associated with a worse prognosis after surgical resection. Keywords: Rectum, MR-Imaging, Abdomen/GI, Oncology, Surgery, Locally Recurrent Rectal Cancer, Tumor Biology Supplemental material is available for this article. © RSNA, 2025.