LAUSR

BACKGROUND The diagnostic implications of lymphatic invasion, venous invasion, perineural invasion, and tumor budding in rectal cancer treated with neoadjuvant chemoradiotherapy are unknown. OBJECTIVE This study was designed to identify the prognostic impact of lymphatic invasion, venous invasion, perineural invasion, and tumor budding in locally advanced rectal cancer treated with neoadjuvant chemoradiotherapy. DESIGN This study was a retrospective cohort study. SETTINGS This study was conducted at the Samsung Medical Center. Grouping was performed based on lymphatic invasion, venous invasion, perineural invasion, and tumor budding status: no-risk group with 0 factors (n = 299), low-risk group with any 1 factor (n = 131), intermediate-risk group with any 2 factors (n = 75), and a high-risk group with 3 or 4 risk factors (n = 32). PATIENTS A total of 537 patients who underwent neoadjuvant chemoradiotherapy, followed by radical operation for locally advanced rectal cancer from January 2010 to December 2015 were included. MAIN OUTCOME MEASURES The main outcome measures were disease-free survival and overall survival. RESULTS The median follow-up period was 77 months, and the 5-year disease-free survival and the 5-year overall survival varied significantly between the groups in stage III (p < 0.001, p < 0.001). The 5-year disease-free survival in stage I differed between the no-risk group and the intermediate-risk group (p=0.026). In stage II, the 5-year disease-free survival and 5-year overall survival differed between the no-risk group and intermediate-risk group p = 0.010, p = 0.045). In multivariable analysis, risk grouping was an independent prognostic factor for both disease-free survival (p < 0.001) and overall survival (p < 0.001). LIMITATION The inherent limitations are associated with the retrospective single center study design. CONCLUSION Lymphatic invasion, venous invasion, perineural invasion, and tumor budding are strong prognostic factors for disease-free survival and overall survival in locally advanced rectal cancer treated with neoadjuvant chemoradiotherapy. Therefore, adjuvant chemotherapy is strongly recommended in patients with positive lymphatic invasion, venous invasion, perineural invasion, and tumor budding. See Video Abstract at http://links.lww.com/DCR/B919.