Who Should Get Lateral Pelvic Lymph Node Dissection after Neoadjuvant Chemoradiation?

BACKGROUND: Despite the use of neoadjuvant chemoradiation and total mesorectal excision for rectal cancer, lateral pelvic lymph node recurrence is still an important problem. OBJECTIVE: This study aimed to determine the indication for lateral pelvic lymph node dissection in post neoadjuvant chemoradiation rectal cancer. DESIGN: This is a retrospective analysis of a prospectively collected institutional database. SETTINGS: This study was conducted at a tertiary care cancer center from January 2006 through December 2017. PATIENTS: Patients who had rectal cancer with suspected lateral pelvic lymph node metastasis, who underwent total mesorectal excision with lateral pelvic lymph node dissection, were included. MAIN OUTCOME MEASURES: The primary outcome measured was pathologic lateral pelvic lymph node positivity. INTERVENTIONS: The associations between lateral pelvic lymph node size on post-neoadjuvant chemoradiation imaging and pathologic lateral pelvic lymph node positivity and recurrence outcomes were evaluated. RESULTS: A total of 64 patients were analyzed. The mean lateral pelvic lymph node size before and after neoadjuvant chemoradiation was 12.6 ± 9.5 mm and 8.5 ± 5.4 mm. The minimum size of positive lateral pelvic lymph node was 5 mm on post neoadjuvant chemoradiation imaging. Among 13 (20.3%) patients who had a <5 mm lateral pelvic lymph node after neoadjuvant chemoradiation, none were pathologically positive. Among 51 (79.7%) patients who had a ≥5 mm lateral pelvic lymph node after neoadjuvant chemoradiation, 33 patients (64.7%) were pathologically positive. Five-year overall survival and disease-specific survival were higher in the histologic lateral pelvic lymph node negative group than in the lateral pelvic lymph node positive group (overall survival 79.6% vs 61.8%, p = 0.122; disease-specific survival 84.5% vs 66.2%, p= 0.088). After a median 39 months of follow-up, there were no patients in the <5 mm group who died of cancer. There were no lateral compartment recurrences in the entire cohort. LIMITATIONS: Being a single-center retrospective study may limit generalizability. CONCLUSIONS: Post-neoadjuvant chemoradiation lateral pelvic lymph node size ≥5 mm was strongly associated with pathologic positivity. No patients with size <5 mm had pathologically positive lymph nodes. Following lateral pelvic lymph node dissection, no patients with a positive lateral pelvic lymph node developed lateral compartment recurrence. Therefore, patients who have rectal cancer with clinical evidence of lateral pelvic lymph node metastasis and post-neoadjuvant chemoradiation lateral pelvic lymph node size ≥5 mm should be considered for lateral pelvic lymph node dissection at the time of total mesorectal excision. See Video Abstract at http://links.lww.com/DCR/B3.