Predictors and survival outcomes of having less than 12 harvested lymph nodes in proctectomy for rectal cancer

Background: Current recommendations suggest that a minimum of 12 lymph nodes (LNs) should be harvested during curative rectal cancer resection. We aimed to assess predictors and survival outcomes of harvesting < 12 lymph nodes in rectal cancer surgery. Methods: A retrospective case–control analysis of factors associated with harvesting < 12 LNs in rectal cancer surgery was conducted. Data were derived from the National Cancer Database 2010–2019. Univariate and multivariate binary logistic regression analyses were performed to determine predictors of harvesting < 12 LNs. Association between harvesting < 12 LNs and 5-year overall survival (OS) was assessed using Cox regression and Kaplan Meier statistics. Results: 67,529 patients (60.8% male; mean age: 61.2 ± 12.5 years) were included. Median number of harvested LNs was 15 (IQR: 11–20); 27.1% of patients had < 12 harvested LNs. Independent predictors of harvesting < 12 LNs were older age (OR: 1.016;p < 0.001), neoadjuvant systemic treatment (OR: 1.522;p < 0.001), neoadjuvant radiation treatment (OR: 1.367;p < 0.001), longer duration of radiation therapy (OR: 1.003;p < 0.001) and abdominoperineal resection (OR: 1.071;p = 0.017). Higher clinical TNM stage and tumor grade, pull-through coloanal anastomosis, and minimally invasive surgery were independently associated with ≥ 12 harvested LNs. < 12 harvested LNs was independently associated with lower 5-year OS (HR: 1.24;p < 0.001) and shorter mean OS (96.7 vs 102.8 months;p < 0.001) than ≥ 12 harvested LNs. Conclusions: Older age, open resection, and neoadjuvant therapy were independent predictors of < 12 harvested LNs. Conversely, higher clinical TNM stage and tumor grade, coloanal anastomosis, and minimally invasive surgery were predictive of ≥ 12 harvested LNs. < 12 LNs harvested was associated with lower OS.