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Background Immune checkpoint inhibitors (ICIs) have redefined treatment for high-burden cancers such as melanoma, non-small cell lung, kidney, and bladder cancers, offering significant survival gains in high-income countries (HICs). 1–3 However, the extent to which these advances have translated globally remains uncertain. The mortality-to-incidence ratio (MIR) serves as a validated proxy for cancer survival and system effectiveness.4–6 We examined global MIR trends over three decades and assessed whether ICI adoption has influenced survival equity across income groups.Methods We extracted age-standardized incidence and mortality estimates for four ICI-indicated cancers (melanoma, kidney, bladder, and lung) from the Global Burden of Disease database (1990–2021), stratified by World Bank income groups. MIR was calculated as mortality divided by incidence. Annual percent change (APC) in MIR was analyzed using linear regression for pre- and post-ICI approval periods. 4 A difference-in-differences (DiD) approach tested MIR slope changes across income groups. Stomach cancer was included as a negative control.Results MIRs for all four ICI-indicated cancers declined from 1990 to 2021 across all income groups, indicating gradual improvements in survival. However, absolute disparities remained substantial. For instance, in 2021, kidney cancer MIR was 0.45 in high-income countries (HICs) versus 0.67 in low-income countries (LICs); melanoma MIR dropped to 0.36 in HICs but remained elevated at 0.87 in LICs. Although some LICs showed notable post-ICI MIR improvements (e.g., melanoma: –9%), these changes did not translate into meaningful reductions in survival disparities ( figure 1). In fact, difference-in-differences (DiD) analysis confirmed no significant narrowing in MIR equity gaps post-ICI (table 1), suggesting that structural access barriers limited the population-level impact of immunotherapy in lower-resource settings.5–8 Conclusions Immune checkpoint inhibitors have transformed cancer treatment in high-resource settings, but their global impact remains unequal. While some low-income countries exhibited modest improvements in MIRs post-ICI, absolute survival gaps relative to HICs persisted, and in many cases widened. DiD analysis confirm no significant narrowing of MIR disparities between income groups in the post-ICI era. These findings highlight the urgent need for equitable investment in diagnostic infrastructure, drug accessibility, and systems delivery to ensure that the promise of immuno-oncology reaches patients worldwide, not just those in wealthy nations. 6–8 References Bray F, Ferlay J, Soerjomataram I, et al. Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide. CA Cancer J Clin. 2021;71(3):209–249.Ribas A, Wolchok JD. Cancer immunotherapy using checkpoint blockade. Science. 2018;359(6382):1350–1355.Sharma P, Allison JP. Immune checkpoint targeting in cancer therapy: toward combination strategies with curative potential. Cell. 2015;161(2):205–214.GBD 2021 Cancer Collaborators. Global burden of 29 cancer groups, 1990 to 2019. JAMA Oncol. 2022;8(3):420–444.Sung H, Ferlay J, Siegel RL, et al. Global cancer incidence and mortality in 185 countries. CA Cancer J Clin. 2021;71(3):209–249.Torre LA, Bray F, Siegel RL, et al. Global cancer incidence and mortality: major patterns and trends. CA Cancer J Clin. 2015;65(2):87–108.Atun R, et al. Expanding global access to cancer medicines. Lancet Oncol. 2015;16(9):1153–1186.Pramesh CS, et al. Delivering affordable cancer care in low-income and middle-income countries. Lancet Oncol. 2014;15(3):e119-e128.Abstract 1209 Figure 1Trends in mortality-to-incidence ratios (MIRs) for ICI-indicated cancers by World Bank income group, 1990–2021. MIRs declined across all income strata for bladder, kidney, melanoma, and lung cancers between 1990 and 2021. However, reductions were most pronounced in high-income countries (HICs), while low-income countries (LICs) showed minimal improvementAbstract 1209 Table 1Impact of Immune Checkpoint Inhibitors on MIR Trends and Equity Gaps by Cancer Type and Income Group. Post-ICI changes in mortality-to-incidence ratios (MIRs) are shown for four major cancers across World Bank income groups