Effect of postradiotherapy neck dissection on nonregional disease sites

IMPORTANCE After chemoradiation for head and neck cancer, more than 90% of patients who achieve a complete clinical response on imaging have their disease regionally controlled without postradiotherapy neck dissections (PRNDs). Because several groups have reported that lymph node involvement also predicts failure at both the primary and distant sites, the extent to which PRND affects nonregional sites of disease remains unclear. OBJECTIVE To evaluate how PRND affects local control (LC) and distant control in patients who achieve a complete clinical response. DESIGN, SETTING, AND PARTICIPANTS We retrospectively reviewed 287 patients (74 of whom underwent PRND) from the University of Illinois at Chicago Medical Center who were treated for stage III/IV disease with definitive chemoradiation from January 1, 1990, through December 31, 2012. INTERVENTIONS Chemoradiation followed by lymph node dissection or observation. MAIN OUTCOMES AND MEASURES End points evaluated included LC, regional control, freedom from distant metastasis, progression-free survival (PFS), and overall survival using first-failure analysis. RESULTS Patients with advanced nodal disease (stage N2b or greater; n = 176) had improved PFS (74.6%vs 39.1%; P < .001), whereas patients with lesser nodal disease had similar PFS. For patients with advanced nodal disease, PRND improved 2-year LC (85.5%vs 53.5%; P < .001), locoregional control with PRND (78.9% vs 45.7%; P < .001), freedom from distant metastasis (79.5%vs 67.5%; P = .03), and overall survival (84.5%vs 61.7%; P = .004) but not regional control (96.9%vs 90.1%; P = .21). The benefit in LC (87.4%vs 66.2%; P = .02) and PFS (80.7%vs 53.4%; P = .01) persisted for those with negative posttreatment imaging results who underwent PRND. On univariate analysis, PRND, alcohol use, nodal stage, and chemoradiation significantly affected 2-year LC and/or PFS. On multivariate analysis, PRND remained strongly prognostic for 2-year LC (hazard ratio, 0.22; 95%CI, 0.07-0.54; P < .001) and PFS (hazard ratio, 0.42; 95%CI, 0.23-0.74; P = .002). CONCLUSIONS AND RELEVANCE Postradiotherapy neck dissection improved control of nonregional sites of disease in patients with advanced nodal disease who achieved a complete response after chemoradiation. Thus, PRND may affect the control of nonnodal sites through possible mechanisms, such as clearance of incompetent lymphatics and prevention of reseeding of the primary and distant sites.