Abstract 859: Impact of obesity in melanoma outcomes: Analysis of data from a multinational randomized controlled sentinel lymph node trial
Authors: Kirchoff Daniel D. , Deutsch Gary B. , Stern Stacey L. , Lavotshkin Simon , Lee Delphine J. , Foshag Leland J. , Faries Mark B. 
Published: August 2015

Abstract
Introduction: In the United States and around the world, obesity rates have been rising. While rates of some cancers are higher in the obese population, the data related to melanoma incidence is conflicting. Furthermore, the impact of obesity on outcomes in melanoma is unknown. We aim to discern the impact of rising body mass index (BMI) on survival and surgical outcomes in melanoma.
Methods: The first Multicenter Selective Lymphadenectomy Trial (MSLT-I) is a multinational randomized controlled trial evaluating the role of sentinel lymph node biopsy in melanoma. We queried this prospective trial database for all patients with height and weight data at the time of enrollment into the trial. Patients were stratified by BMI as obese (BMI ≥30) or not obese (BMI&lt;30). Patient age, sex, Breslow thickness, and lymph node status were assessed for their impact on melanoma specific survival (MSS) and surgical complications. Pathologic data and primary site data were also analyzed with regards to obesity.
Results: A total of 1,839 patients were included in the analysis, 741 from the observation group (OBS, no sentinel lymph node biopsy), and 1098 from the sentinel node group (SLN). 376 patients (20%) were obese and 1,463 (80%) were not. MSS at 5 years was 88.8% (±1.7) for obese patients and 82.2% (±1.0) for non-obese patients (p = 0.0512, univariate). A small minority of patients were underweight (n = 27, 1.5%, BMI &lt; 18.5) and they experienced a trend towards worse survival than obese patients (5-yr MSS 79.0% ±8.4). We assessed BMI in a multivariable analysis as a continuous and categorical variable and found a consistent direct association with MSS (for BMI ≥30: HR 0.69 [0.52-0.91], p = 0.010). Multivariable analysis identified decreased BMI, male sex, older age, thicker Breslow level, lymphatic spread, and ulceration as significant predictors of worse survival. Despite a trend towards increased local complications in the obese (23.1% vs. 20.5%, p = 0.267), there was no significant difference in rate of complications based on BMI. The distribution of primary melanoma sites was not different among obese and non-obese populations and there was no difference in pathologic variables (Breslow thickness, ulceration, regression, number of lymph nodes excised, or presence of tumor infiltrating lymphocytes). Conclusions: In this prospective trial database, obesity offers a protective effect on survival without a significantly increased rate of complications. Future studies may look for obesity-related factors and mechanisms to explain the improved outcomes.
Citation Format: Daniel D. Kirchoff, Gary B. Deutsch, Stacey L. Stern, Simon Lavotshkin, Delphine J. Lee, Leland J. Foshag, Mark B. Faries. Impact of obesity in melanoma outcomes: Analysis of data from a multinational randomized controlled sentinel lymph node trial. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 859. doi:10.1158/1538-7445.AM2015-859