Evaluating different adoption scenarios for TIL-therapy and the influence on its (early) cost-effectiveness.

First, 14 adoption scenarios for TIL-therapy were drafted using a Delphi approach with a group of involved experts. Second, the likelihood of the scenarios taking place within 5 years was surveyed among international experts using a web-based questionnaire. Third, based on the questionnaire results and recent literature, scenarios were labeled as being either "likely" or "-unlikely". Finally, the cost-effectiveness of TIL treatment involving the "likely" scored scenarios was calculated.

Incorporating possible future developments, TIL-therapy was calculated to be cost-effective compared to ipilimumab in the majority of "likely" scenarios. These scenarios could function as facilitators for adoption. Contrary, TIL therapy was expected to not be cost-effective when sold at commercial prices, or when combined with ipilimumab. These scenarios should be considered in the adoption decision as these may act as crucial barriers.

Twenty-nine experts from 12 countries completed the questionnaire. The scenarios showed an average likelihood ranging from 29 to 58%, indicating that future developments of TIL-therapy were surrounded with quite some uncertainty. Eight of the 14 scenarios were labeled as "likely". The net monetary benefit per patient is presented as a measure of cost-effectiveness, where a positive value means that a scenario is cost-effective. For six of these scenarios the cost-effectiveness was calculated: "Commercialization of TIL production" (the price was assumed to be 3 times the manufacturing costs in the academic setting) (-€51,550), "Pharmaceutical companies lowering the prices of ipilimumab" (€11,420), "Using TIL-therapy combined with ipilimumab" (-€10,840), "Automatic TIL production" (€22,670), "TIL more effective" (€23,270), "Less Interleukin-2" (€20,370).

Treatment with tumor-Infiltrating Lymphocytes (TIL) is an innovative therapy for advanced melanoma with promising clinical phase I/II study results and likely beneficial cost-effectiveness. As a randomized controlled trial on the effectiveness of TIL therapy in advanced melanoma compared to ipilimumab is still ongoing, adoption of TIL therapy by the field is confronted with uncertainty. To deal with this, scenario drafting can be used to identify potential barriers and enables the subsequent anticipation on these barriers. This study aims to inform adoption decisions of TIL by evaluating various scenarios and evaluate their effect on the cost-effectiveness.