E324: A Cost-Effectiveness Analysis of Tumor Infiltrating Lymphocytes (TIL) versus Pembrolizumab for Metastatic Melanoma

Treatment for metastatic melanoma has evolved with immune checkpoint inhibition (CPI) infusions. In contrast, tumor-infiltrating lymphocytes (TIL) have been utilized as a novel therapeutic modality for malignant melanoma with durable, long-lasting effects from a single treatment. Recent data has shown that progression-free survival (PFS) is significantly longer for patients treated with TIL therapy than CPI monotherapy. Still, more is needed to know about the cost-effectiveness of this treatment modality, which is associated with high up-front costs and adverse events during the acute treatment phase. This study proposes a framework to assess cost-effectiveness by comparing checkpoint inhibition versus TIL therapy for metastatic melanoma.

Methods:

We performed a three-state Markov model (progression-free, progression, death) to compare the cost-effectiveness of pembrolizumab versus TIL therapy. Outcome data from the Keynote 006 trial and outcome data for TIL therapy were extracted from a recent multi-center randomized trial to create transition probabilities. The cost for TIL therapy was estimated from adoptive cell therapies, such as CAR-T, while costs for Pembrolizumab was determined from Centers for Medicare and Medicaid data. Utility and direct adverse event costs were estimated from published literature. Quality-adjusted life-years (QALYs), lifetime costs, and incremental cost-effectiveness ratio (ICER) were calculated at a willingness-to-pay threshold of $200,000 per QALY.

Results:

Pembrolizumab administration every three weeks was less costly than TIL therapy, with incremental QALY and ICER for TIL therapy favoring Pembrolizumab. Over a lifetime, TIL accrued a total cost of $412,975 (95% CI 403,392, 421,220) and a QALY of 19.66(95% CI 15.98, 23.57). Pembrolizumab monotherapy accrued a total cost of $211,600 (95% CI $193,600, $230,300). The incremental QALY for Pembrolizumab was 21.92 (19.43,24.64). At our willingness-to-pay threshold of $200,000, the ICER for TIL therapy was larger than that for immunotherapy.


Conclusions:

Cost-effectiveness analysis demonstrated pembrolizumab monotherapy for patients with metastatic melanoma was cost-effective to TIL therapy based on current cost assumptions similar to CAR-T. As cell therapy becomes a more prevalent treatment modality for melanoma upon commercialization, strategies to reduce costs will be critical for managing metastatic melanoma.