Differential effect of tumor budding on the benefit of adjuvant chemotherapy in stage II colorectal cancer: a retrospective observational study.

ABSTRACT

Background: Tumor budding (TB) has been shown to be a poor prognostic indicator after colorectal cancer (CRC) surgery. The aim of the present study is to evaluate the predictive role of morphological features (e.g., the number, structure, and location of tumor buds, and their reaction with the extracellular mesenchyme) in postoperative adjuvant chemotherapy in surgically resectable stage II CRC. Methods: Between 2016 and 2019, 336 patients with stage II CRC who underwent radical surgery were enrolled in this study. TB status was determined according to the criteria adopted at the 2016 International Tumor Budding Consensus Conference (ITBCC). We retrospectively recorded all the clinical and pathological data and assessed the effect of different types of TB status on patients' recurrence-free survival (RFS) and overall survival (OS). Results: Of the 336 patients, 173, 88, and 75 were budding grade 1 (BD1), BD2, and BD3, respectively. The 5-year RFS rates were 84.6%, 81.2%, and 68.0% (P=0.01), and the 5-year OS rates were 91.0%, 83.3%, and 76.2% (P=0.007) in BD1, BD2, and BD3, respectively. TB grade was strongly associated with vascular invasion status and mucinous adenocarcinoma, and BD3 was detected in 51.7% of patients with positive vascular invasion. The multivariate analysis showed that only age, perineural invasion, and TB grade [BD2 vs. BD1, hazard ratio (HR) =1.468, 95% confidence interval (CI) 0.703-3.063, P=0.30; BD3 vs. BD1, HR =2.310, 95% CI 1.154-4.625, P=0.01] had an independent effect on RFS. In addition, the Kaplan-Meier curve analysis showed that BD3 patients had the worst RFS (P=0.01). The OS of the adjuvant chemotherapy group was significantly improved compared to that of the surgery-only group in the BD1/2 patients (HR =0.278, 95% CI 0.114-0.676, P=0.005) but not in the BD3 patients with significant interaction (Pinteraction=0.03). Conclusions: Our results indicate that TB could play a subsidiary role in selecting stage II CRC patients who could achieve a favorable prognosis with chemotherapy.