Prognostic Impact of Lymphatic Invasion, Venous Invasion, Perineural Invasion, and Tumor Budding in Rectal Cancer Treated with Neoadjuvant Chemoradiotherapy Followed by Total Mesorectal Excision

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 aimed 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 was a retrospective cohort study. SETTINGS: This study was conducted at the Samsung Medical Center. Grouping was performed on the basis of lymphatic invasion, venous invasion, perineural invasion, and tumor budding status: no-risk group with 0 factor (n = 299), low-risk group with any 1 factor (n = 131), intermediate-risk group with any 2 factors (n = 75), and high-risk group with 3 or 4 risk factors (n = 32). PATIENTS: 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 and overall survival. RESULTS: Disease-free and overall survival varied significantly between the groups in stage III (p < 0.001 and p < 0.001). Disease-free survival in stage I differed between the no-risk group and the intermediate-risk group (p = 0.026). In stage II, disease-free and overall survival differed between the no-risk group and the intermediate-risk group (p = 0.010 and p = 0.045). In multivariable analysis, risk grouping was an independent prognostic factor for both disease-free (p <0.001) and overall survival (p < 0.001). LIMITATIONS: The inherent limitations are associated with the retrospective single-center study design. CONCLUSIONS: Lymphatic invasion, venous invasion, perineural invasion, and tumor budding are strong prognostic factors for disease-free 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.