Pretreatment risk prediction for distant metastasis in locally advanced rectal cancer.

248 Background: Distant metastasis is the most common form of recurrence in locally advanced rectal cancer. This study aimed to identify pretreatment risk factors for distant metastases in patients with locally advanced rectal cancer. Methods: This single-institution retrospective study included 285 patients who underwent preoperative chemoradiotherapy followed by surgical resection between January 2016 and December 2020. Pretreatment clinical characteristics, MRI findings, and blood profiles were analyzed to investigate its association with distant metastasis. Results: With a median follow-up of 39 months (range: 6 - 78), 42 patients had confirmed distant metastasis (14.7%), and most distant metastasis occurred within three years (40 patients, 95.2%). In the multivariate analysis, pretreatment extramural venous invasion (EMVI, HR = 3.05, p < 0.001) and carcinoembryonic antigen (CEA) > 10 ng/mL (HR = 2.77, p = 0.002) were independent predictors of distant metastasis. Patients with no adverse factors had significantly better distant metastasis-free survival than patients with 1 or 2 adverse features (92% vs. 70% vs. 59% (p < 0.001) at 3 years). Conclusions: Pretreatment CEA and EMVI have predictive significance for distant metastasis in locally advanced rectal cancer. Our findings may help select patients who may benefit from intensified preoperative treatment, such as total neoadjuvant therapy.