Active and latent tuberculosis infections in patients treated with immune checkpoint inhibitors in a non-endemic tuberculosis area

Background: Immune checkpoint inhibitors (ICIs) blocking inhibitory immune pathways (e.g., programmed cell death protein-1/-ligand1 [PD-1/PD-L1]) have revolutionized cancer therapy for numerous malignancies. There have been an increasing number of cases of active tuberculosis (TB) reported in association with ICI use, and recent data suggest alterations in immune responses in TB by ICI. The aim of this study was to characterize the frequency of latent tuberculosis infection (LTBI) and active TB in a large cohort of ICI-treated patients in a low TB incidence area. Methods: We conducted a retrospective review of all ICI-treated patients tested for TB between January, 1997 and August, 2018. Data extracted included patient demographics, TB risk factors, latent/active TB diagnosis and treatment, tumor type, ICI used, immunosuppressive medications, and mortality related to TB. Results: We identified 1844 ICI-treated patients, including 30 abnormal TB test results. Two patients were diagnosed with active TB, both prior to starting ICI therapy. One patient was treated for TB prior to starting ICI and the other patient was successfully treated concurrently. Seven patients were diagnosed with LTBI and none developed active TB. Twenty patients had indeterminate interferon gamma release assays (IGRA). Conclusion: Despite recent reports of TB in patients taking ICI, we found no patients developing TB during ICI therapy in our large retrospective cohort of ICI-treated cancer patients in a non-endemic TB area. The high rate of indeterminate IGRA results suggests the need for prospective research with better diagnostics to quantify the actual risk of TB in this patient population.