OBJECTIVES: PD1/PD-L1 blockers are regarded as new SoC for certain cancer types. We aimed to project the potential national number of cancer patients who would be eligible for PD1/PD-L1 inhibitors in Taiwan and also to estimate additional total life years gained with these therapies. METHODS: The indications of PD1/PD-L1 inhibitors approved by Taiwan FDA as 07-09-2018 were reviewed to finalize the scope of projection. Newly diagnosed cancer patients were identified in the 2012-14 dataset of National Cancer Registry for these indications. Using the ID codes of these patients, their individual treatment history data was extracted from the 2012-15 dataset of National Health Insurance Database. Patient level data was analyzed to estimate the number of patients remained in each treatment line. The population census and historical growth rate of patient number was estimated and applied together with PDL1 prevalence rate for projection of eligible patient numbers. The reported incremental median overall survival gain for PD-1/PD-L1 inhibitors was applied accordingly to each projected patient number by indication to estimate the additional total life years gained. RESULTS: Based on the real world datasets, the annual number of patients who are eligible for PD1/PD-L1 inhibitors from 2019 to 2023 were projected to be 101 to 115 for MEL 1L; 1,200 to 1,520 for NSCLC 1L with TPS≥50%; 1,556 to 1,849 for NSCLC 2L; 1,440 to 1,574 for HNSCC 2L, 285 for GC 3L; and 152 to 193 for UC 2L. A total gain of additional 2,499 to 3,073 life-years was estimated for treatment with PD-1/PD-L1 inhibitors instead of chemotherapies for eligible patients in Taiwan. CONCLUSIONS: This study informs an annual total of 4,734 to 5,536 cancer patients who were estimated to be eligible for PD-1/PD-L1 inhibitors in Taiwan. This projection will be useful in future related research and policy planning such as resource and budget allocation.