Tumor regression pattern may impact the prognosis of rectal cancer patients with tumor regression grade 1 after neoadjuvant chemoradiotherapy.

Tumor regression grade (TRG) is evaluated by calculating the proportion of residual tumor to stromal fibrosis, which can reflect the tumor response to neoadjuvant chemoradiotherapy (NCRT) in patients with locally advanced rectal cancer (LARC). Overall, patients with TRG1 show good sensitivity to NCRT but the long-term survival for these patients remains different. This study aimed to assess the prognostic factors in patients with TRG1. LARC patients who underwent NCRT and radical surgery were included. TRG was evaluated according to the National Comprehensive Cancer Network guidelines. The association between clinicopathological factors and survival outcomes was assessed in patients with TRG1. Overall survival (OS) and disease-free survival (DFS) were evaluated using both Kaplan-Meier analyses and Cox proportional hazards models. Of the 393 LARC patients, 104 (26.5%) were diagnosed with TRG1. The 5-year OS rates and 5-year DFS rates of patients with TRG1 were 90.9% and 72.2%, respectively. In patients with TRG1, the tumor regression pattern (P = 0.001), pathologic tumor node metastasis (TNM) stage (P = 0.002), neoadjuvant rectal score (P = 0.024), T downstaging (P = 0.022), and baseline carcinoembryonic antigen level (P = 0.038) were associated with DFS in univariate analysis. Only the tumor regression pattern showed prognostic significance for DFS in multivariate analysis (P = 0.003). The group with tumor shrinkage had a higher OS rate than the tumor fragmentation group but the difference in the OS rates between the two groups was not significant (P = 0.196). TRG could be a prognostic variable for LARC patients receiving NCRT. In patients with TRG1, the tumor regression pattern may represent another useful prognostic factor to better individualize the prognosis.