LAUSR

e20703 Background: Trial results from KEYNOTE-407 have recently led to the FDA approval for pembrolizumab + carboplatin + paclitaxel/nab-paclitaxel (pembrolizumab+chemo) in previously untreated metastatic squamous NSCLC. This is the only first-line indication for squamous NSCLC regardless of tumor expression status. Our objective was to evaluate the cost-effectiveness of pembrolizumab combination therapy in this setting from the US payer perspective. Methods: Using data from KEYNOTE-407, we developed a partitioned survival decision model to estimate the lifetime costs and effectiveness of pembrolizumab+chemo vs. chemo alone in the first-line treatment of metastatic squamous NSCLC. The base case used a Weibull curve selected based on minimum AIC/BIC and best graphical fit to extrapolate in-trial survival to a lifetime horizon. First- and second-line therapy resource use and adverse event (AE) rates were derived from KEYNOTE-407. Utility data and AE management were obtained from published literature and national sources. Direct medical costs were adjusted to 2018 US dollars, and future costs and outcomes were discounted at 3% per year. We estimated life years (LY), quality-adjusted life years (QALYs), and costs over a lifetime horizon. One-way and probabilistic sensitivity analyses were also conducted. Results: In the base case, pembrolizumab+chemo resulted in 0.51 more LYs, 0.36 more QALYs, and $233,246 in healthcare costs vs. chemo alone. Costs per LY and QALY gained were $216,180 and $309,004, respectively. One-way sensitivity analyses indicated that the results were most sensitive to survival and pre-progression utility inputs. In a threshold analysis, we found that the cost of pembrolizumab+chemo would need to be reduced by 24% per course of therapy ($176,175) in order to be cost-effective at $150,000/QALY. Conclusions: Based on current available data, our analysis suggests first-line pembrolizumab-based combination therapy in metastatic squamous NSCLC is unlikely to be cost-effective relative to implied willingness to pay in cancer in the U.S. (ie < $150,000 per QALY). Future studies should reassess cost-effectiveness as trial data mature.