​obesity and metastatic melanoma: A national perspective from the pre-immune checkpoint inhibitor era.

Abstract

e21032 Background: There is an ongoing debate about correlation of obesity with favorable outcomes in patients with metastatic melanoma receiving treatment. Our study measured the differences in in-hospital outcome parameters such as length of stay (LOS), cost and mortality in patients with metastatic melanoma with respect to obesity. Methods: We used National Inpatient Sample (NIS) dataset from 2008 to 2014 to identify the diagnosis of Metastatic melanoma (ICD-9 code:172.9) among hospitalized patients. Data was matched and weighted to obtain a nationally representative sample for analysis. The AHRQ comorbidity measure of obesity was utilized to identify obesity as a coexisting medical condition that is not directly related to the principal diagnosis. Categorical and continuous variables were tested using Chi-square test and Student t-test respectively. Multivariate hierarchical regression was used for the analysis of primary outcomes of interest. Results: We identified a total of 1,809 cases of metastatic melanoma from 2008 to 2014. Among them, 908 (50.19%) were obese and 901 (49.80%) non-obese. 195 out of the 1,809 (10.77%) patients were treated with high dose infusion of IL-2. Overall, the mean LOS (≈6.03 days [non-obese] vs ≈5.72 days [obese], p = 0.949) and mean cost of hospitalization (16720.28$ vs 17639.95$, p = 0.428; mean difference of 919.67$) was not significantly different based on obesity as a comorbid condition. The mortality rate was found to be significantly lower in obese patients (41% vs. 59%, p = 0.017), but did not reach statistical significance on logistic regression analysis (OR:0.95, p = 0.130). Further subgroup analysis of patients with metastatic melanoma who received high dose IL-2, we found no significant differences in mean LOS (5.03 vs 7.03, p = 0.14) as well as mean cost of hospitalization (27432.72$ vs 41881.13$, p = 0.485) between non-obese and obese patients. However, the in-hospital mortality for patients undergoing high dose IL-2 therapy could not be studied given no cases of in-hospital mortality occurred in this subgroup. Conclusions: Our study demonstrates that there are no significant differences in in-hospital outcomes for patients with metastatic melanoma with respect to obesity, even in the subgroup of patients treated with IL-2 immunotherapy. Thus, there is a need for further studies to adequately understand the exact biological mechanism of obesity in metastatic melanoma, the influence of obesity on immunotherapy outcomes and its translation into patient care outcomes.