Intensity Modulated Radiation Therapy Improves Survival in Early-Stage Supraglottic Larynx Cancer

Abstract

Early stage supraglottic larynx cancers treated with definitive radiotherapy (RT) require treatment of the bilateral neck because of high rates of regional spread. Compared to older techniques, modern intensity modulated radiation therapy (IMRT) has been shown to precisely target tumor and draining nodal regions with the potential to spare organs at risk including those essential for prevention of aspiration. However, previous hospital-based studies have demonstrated decreased survival associated with the use of IMRT compared to 3D and 2D radiotherapy techniques in glottic larynx. We used the National Cancer Data Base (NCDB) to study the impact of the IMRT technique on overall survival of supraglottic tumors. We searched the NCDB for cT1-T2 N0 supraglottic larynx cancer managed with definitive RT alone between 2004 to 2012. Mortalities within 3 months were excluded to minimize survivorship bias. All relevant demographic, tumor specific, and treatment data were recorded. Propensity score matching (PSM) was utilized to match 1:1 patients treated with IMRT with patients treated with 3D/2D techniques for all treatment and demographic variables. The overall survival (OS) benefit of IMRT over non-IMRT techniques was estimated using univariate (UVA) log-rank tests and multivariate (MVA) Cox models. Factors demonstrating significance of P<0.05 on UVA analysis were included in MVA analysis. A forward stepwise selection was used to confirm robustness of model parameters. From 2004 to 2012, a total of 2,429 patients with cT1-2N0 supraglottic larynx cancers who received definitive RT were identified, 907 of which were treated with IMRT. A total of 1,814 patients were identified within the PSM cohort, with a median follow-up of 39 months (range 3-129 months). After matching, patients who received IMRT (N=907) were more likely to be treated after 2008 than patients with no IMRT (44% vs. 71%). Otherwise there was no significant difference (p > 0.05) in any demographic or treatment factor between groups. In total there were 756 deaths, with a median survival of 81 months (95% CI 73–89 mos.) in the IMRT patients and 68 months (95% CI 63-73 mos.) for the non-IMRT patients. IMRT was significantly associated with improved OS in UVA (HR: 0.81 (0.70-0.94 p<0.001) analysis, along with age younger than 50, female gender, well differentiated disease, T1 stage, good performance status, income > $38K, and private insurance, treatment at academic center. In the MVA Cox proportional hazards models, IMRT remained significantly associated with improved overall survival (HR: 0.85 (0.73-0.98) p<0.001). All other factors entered remained significant in MVA except grade. This largest hospital-based-analysis indicates IMRT techniques are associated with improved OS in early-stage cancer of the supraglottic larynx when compared to 3D and 2D techniques.