Comparison of conventional unstained lymph nodal harvesting vs methylene blue-stained lymph nodal harvesting in colorectal specimen in staging left-sided colorectal carcinoma: a randomized controlled trial.

ABSTRACT

BACKGROUND: The management and prognosis of colorectal carcinomas (CRCs) are related to the stage of the disease, which, in turn, relies on the lymph node harvest from the surgical specimen. The guidelines recommend that at least 12 lymph nodes are required, which is not achieved in most resections. In this study, we propose a method to improve the lymph node yield in such cases. This study aimed to determine whether ex vivo injection of methylene blue into the inferior mesenteric artery or its branches improves lymph node retrieval in left-sided CRCs. METHODS: This study was conducted as a single-center, double-blinded, superiority randomized controlled trial. Patients who underwent elective surgery for left-sided CRCs with curative intent were randomized into 2 groups stained and unstained. The sample size was calculated as 66. In all patients, details of disease stage, history of neoadjuvant therapy, and number of isolated lymph nodes were recorded. RESULTS: The mean number of lymph nodes extracted from the stained group was significantly higher than that from the unstained group (15.9 ± 5.2 vs 9.1 ± 5.7, respectively; P < .001). Among the patients who had received neoadjuvant therapy, the yield was higher in the stained group (P < .001). The yield was found to be greater in patients who had undergone upfront surgery than in those who had undergone neoadjuvant therapy, even in the stained group (100% vs 66.7%, respectively). CONCLUSION: The use of methylene blue injection into resected specimens of left-sided CRCs significantly improved the lymph node yield.