Evaluation of serial interferon-gamma release assay testing in lung cancer patients treated with immune checkpoint inhibitors

<b>Background:</b> Infectious diseases, such as tuberculosis (TB), have been recognised as emerging concerns during immunotherapy with immune checkpoint inhibitors (ICIs). We aimed to evaluate the interferon-gamma releasing assay (IGRA) conversion rate and incidence of active TB during immunotherapy to understand the incidence of reactivation of TB after the induction of ICIs. <b>Methods:</b> We prospectively assessed IGRA in patients with NSCLC who received ICI monotherapy at the time of diagnosis and at 6 and 12 months after ICI treatment. We also assessed CT scan images for evaluating whether active TB occurred when patients demonstrated positive IGRA results at any time. <b>Results:</b> A total of 178 patients were prospectively recruited between January 2017 and December 2020. Of these, 123 patients completed serial IGRA. Among these 123 patients, 18 (14.6%) had a positive IGRA, 101 (82.1%) had a negative IGRA, and four (3.3%) had an indeterminate IGRA at baseline. Three (2.44%) patients demonstrated a negative conversion of IGRA, while three (2.44%) patients demonstrated a positive conversion of IGRA during immunotherapy. One patient with a positive conversion of IGRA and another with sustained negative IGRA exhibited the development of active pulmonary TB during immunotherapy. <b>Conclusions:</b> This study revealed that 2.44% of patients demonstrated positive conversion of IGRA, while 1.6% developed active TB. Of the three patients with the positive conversion of IGRA, the development of active pulmonary TB during immunotherapy was confirmed in one patient. Physicians should consider the development of TB during immunotherapy with ICIs.