Tumor Budding as a Prognostic Marker in Rectal Cancer Patients on Propensity Score Analysis

Tumor budding is associated with adverse histology. It is a predictor of poor oncologic outcomes in colorectal cancer. However, it remains unclear whether tumor budding is a predictor of poor prognosis for rectal cancer patients regardless of neoadjuvant chemoradiotherapy (nCRT). This study analyzed 2888 rectal cancer patients who underwent radical surgery from 2007 to 2014. Among these patients, 939 underwent nCRT while 1949 did not receive nCRT. Tumor budding was defined as positive if the number of isolated tumor cells or small clusters of up to five tumor cells at the invasive front of the tumor was five or more. If the number was less than five, it was defined as negative. Patients were categorized according to tumor budding status. We used 1:1 propensity score matching to adjust for potential baseline confounders between the two groups. Among 2888 patients, 939 received nCRT while 1949 did not receive nCRT. A total of 418 patients who received nCRT were matched (209 in each group). A total of 1024 patients without nCRT were also matched (512 in each group). In matched patients, 5-year overall survival (OS) and 5-year disease-free survival (DFS) rates for the positive budding group were significantly lower than those in the negative budding group regardless of nCRT. On multivariate analysis of prognostic factors, positive budding was associated with poorer disease-free survival independent of nCRT. Tumor budding positivity is a prognostic indicator of poor outcomes in rectal cancer patients regardless of neoadjuvant chemoradiotherapy.