BACKGROUND: The adverse outcomes and costs of immunotherapy (IT) have yet to be fully explored. Our study aims to assess the association between the use of IT in patients with metastatic renal cell carcinoma (mRCC) and the burden of illness (BOI), including coagulopathy, arrhythmia, and disparities. METHODS: The study used US national data to investigate the association between the use of IT in the mRCC and the BOI. The BOI was measured by total charges and length of stay (LOS). Additionally, we examined coagulopathy, arrhythmia, and disparities in these outcomes. This investigation was conducted using generalized linear models (glm). RESULTS: Of 28,535 patients who had mRCC, 230 had previously received IT. In the adjusted glm, after accounting for other variables, "IT" was found to be associated with higher total charges- (coeff = 7.67
95% CI 4.86 - 12.09). There was no association with IT and LOS. Coagulopathy (aOR = 5.61
95% CI 2.40 - 13.14) and arrhythmia (aOR = 4.34
95% CI 2.20 - 8.55) were associated with IT treatment. Moreover, compared to males, females had a lower cardiac arrhythmia risk (aOR 0.83, 95% CI 0.72-0.98). Non-whites, compared to Whites, had a higher total charge (1.21, 95% CI 1.13-1.29), higher coagulopathies (aOR 1.25
95% CI 1.01-1.54), but lower cardiac arrhythmia risk (aOR 0.57
95% CI 0.47-0.69). CONCLUSION: Although IT has become increasingly important in treating mRCC, this is the first time real-world data on the costs, negative consequences, and disparities of IT are examined. The results may have important implications for creating innovative, supportive care models for this population.