Resected irradiated rectal cancers: Are twelve lymph nodes really necessary in the era of neoadjuvant therapy?

BACKGROUND: Our study aims to identify the minimum number of lymph nodes (LN) associated with improved survival in patients who underwent NRT for stage II-III rectal cancer. METHODS: Adults with clinical stage II and III rectal adenocarcinoma in the National Cancer Data Base were stratified by NRT. Multivariable Cox regression modeling with restricted cubic splines was used to determine the minimum number of LNs associated with improved survival. RESULTS: Of 38,363 patients, 76% received NRT. After adjustment, a LNY≥12 was associated with improved survival among patients receiving NRT (HR 0.79, p < 0.0001) and those without NRT (HR 0.88, p = 0.04). Among patients receiving NRT, factors independently associated with LNY≥12 were younger age, private insurance, low comorbidity score, a recent year of diagnosis, higher T stage and grade, APR resection, and academic institution. CONCLUSIONS: A minimum LNY of 12 confers a survival benefit for rectal cancer patients regardless of receiving neoadjuvant radiation therapy.