Saigal, Christopher S.

395 Background: Patients with BCG-unresponsive carcinoma in situ (CIS) are treated with radical cystectomy (RCx) or salvage intravesical chemotherapy (SIC). Recently, the FDA approved pembrolizumab for BCG-unresponsive CIS +/- papillary tumors. Given the costs and toxicities of pembrolizumab, it remains unclear whether its benefits are sufficient to warrant widespread use for BCG-unresponsive CIS. To that end, we conducted a cost-effectiveness analysis comparing pembrolizumab with RCx and SIC (using gemcitabine-docetaxel as the prototypical regimen) for patients with BCG-unresponsive CIS. Methods: A decision-analytic Markov model compared pembrolizumab, SIC (with gemcitabine-docetaxel), and RCx for patients with BCG-unresponsive CIS +/- papillary tumors who are RCx candidates (index patient 1) or are unwilling/unable to undergo RCx (index patient 2). Each treatment option was a Markov node containing distinct variations of the following health states: surveillance, recurrence, progression to MIBC, progression to metastasis, treatment toxicity, and death. Incremental Cost-Effectiveness Ratios (ICERs) were compared using a willingness-to-pay threshold of $100,000/Quality-adjusted life year (QALY). The model used a US Medicare perspective with a 5-year time horizon for the base case. One-way and probabilistic sensitivity analyses were performed for all model parameters. Results: For index patient 1, pembrolizumab was not cost-effective vs. RCx (ICER $1,403,008) or SIC (ICER $2,011,923). One-way sensitivity analysis revealed that pembrolizumab only became cost-effective relative to RCx with a > 93% price reduction. Relative to RCx, SIC was cost-effective for time horizons < 5 years and nearly cost-effective at 5 years (ICER $118,324). One-way sensitivity analysis revealed that SIC became cost-effective relative to RCx if its risk of recurrence or metastasis at 2 years was less than 55% or 5.9%, respectively. For index patient 2, pembrolizumab required > 90% price reduction to be cost-effective vs. RCx (ICER $1,073,240). Probabilistic sensitivity analyses revealed that pembrolizumab was unlikely to be cost-effective even at high willingness-to-pay thresholds. Further sensitivity analyses found that no two-way combination of extrapolated values resulted in pembrolizumab being favored over RCx or SIC for either index patient. Conclusions: Based on decision-analytic Markov modeling of treatment options for patients with BCG-unresponsive CIS, pembrolizumab was unlikely to be cost-effective without a > 90% price reduction. While both RCx and SIC were more cost-effective than pembrolizumab, further studies may validate the cost-effectiveness of gemcitabine-docetaxel relative to RCx if the recurrence and metastasis thresholds are met. Overall, our model supports the preferential use of RCx and SIC over pembrolizumab for BCG-unresponsive CIS.