Tumour budding predicts increased recurrence after curative resection for T2N0 colorectal cancer

Background: Tumour budding is defined as the presence of a cluster of fewer than 5 cells along the invasive margin. It may confer a worse prognosis in colorectal cancer, but its importance in pT2N0 colorectal cancer is unknown. This study aimed to determine the prognostic value of tumour budding in pT2N0 colorectal cancer. Methods: This was a retrospective cohort study with prospective assessment of tumour budding by 2 pathologists. We included all patients who underwent elective curative resection for pT2N0 colorectal cancer except those with hereditary colorectal cancer syndromes, inflammatory bowel disease or positive resection margins, those who received neoadjuvant or adjuvant therapy and those who died within 90 days of operation. Patients were classified as having high-grade tumour budding (>= 10 budding foci per high-power field) or low-grade tumour budding (< 9 budding foci per high-power field). The main outcome measure was locoregional or distant recurrence. Results: Of 85 patients, 36 had high-grade tumour budding and 49 had low-grade tumour budding. The overall recurrence rate was 11% (9/85) and median follow-up was 41.0 months (interquartile range 22.0-68.0). Interrater reliability for tumour budding assessment was excellent (kappa = 0.86, 95% confidence interval [CI] 0.76-0.96). There were more recurrences in patients with high-grade tumour budding (7/36, 19.4% v. 2/49, 4.1%; p = 0.020). On multivariate analysis, after we adjusted for confounders, the presence of high-grade tumour budding was independently associated with recurrence (hazard ratio 5.11, 95% CI 1.01-25.9). Conclusion: Tumour budding was independently associated with increased recurrence after pT2N0 colorectal cancer resection. It offers additional prognostic information that may affect treatment strategy.