Abstract
BACKGROUND: Tumor deposits (TDs) may have a worse prognosis in rectal cancer, but their significance in the neoadjuvant era is less certain. Post-treatment TDs might even be a sign of tumor response. The present study aimed to assess the clinical significance of TDs detected before and after neoadjuvant therapy, and to investigate the impact of neoadjuvant therapy-induced TDs changes on oncological outcomes. METHODS: A retrospective cohort analysis using our hospital records from 2017 to 2019 was carried out. All patients received preoperative long-course chemoradiotherapy and part of them received total neoadjuvant therapy. RESULTS: A total of 132 patients with cT3-4N+M0 were included. mrTDs were observed in 40 (30.3%) patients. 40% of the patients had two or more mrTDs. 64.4% of mrTDs located in the mesorectal fat. mrTDs were associated with mrT4 stage, lymph node invasion, threatened mrMRF, and positive mrEMVI. 51.4% of mrTDs positive patients achieved complete response after neoadjuvant therapy. 3-year disease-free survival (DFS) and overall survival (OS) were worse in mrTD positive patients (3y-DFS: 42.5% vs 73.9%, P < 0.001; 3y-OS: 55% vs 82.9%, P < 0.001). Among the patients with mrTDs, those who became ypTDs- after neoadjuvant therapy had better outcome compared to the ypTDs+ patients (3y-DFS: 52.6% vs 22.2%, P = 0.022; 3y-DMFS: 63.2% vs 27.8%, P = 0.025). Distant metastasis occurred earlier and more frequently in ypTDs+ group, and multiple metastasis were more common. ypTDs and TDs' different response to neoadjuvant therapy were prognostic factors of overall survival in multivariate analysis. CONCLUSIONS: The presence of mrTDs and the poor regression of mrTDs in cT3-4N+M0 rectal cancer after neoadjuvant treatment are associated with advanced disease and worse outcome. Patients with ypTDs+ after neoadjuvant therapy have dismal outcome, which call for more innovative treatment.