ItemImmune-related thyroid dysfunction in lung cancer patients treated with PD-1/PD-L1 checkpoint inhibitors.(2023-04) Bulusu, Venkata; Jessop, Susan; Paul, Sherin; Chapman, Timothy; Aslam, Shahzeena; Jeffs, Yvonne; Punnen, Geethu; Geetha, Anil; Hutka, MargaretIntroduction: Thyroid dysfunction as an immune related adverse event (IrAE) is the most commonly occurring endocrine IrAE. We present our experience with Thyroid IrAE in lung cancer patients treated from 2017-2022 at the Primrose Oncology Unit. Method(s): Clinical records of lung cancer patients treated with PD-1PD-L1 inhibitors in the Primrose Oncology Unit were reviewed. Demographics, histology, serial thyroid test results, type of PD-1PD-L1 inhibitor and endocrine interventions were collected. Time kinetics of thyroid dysfunction were plotted against the total number of PD-1/PD-L1 cycles received. Result(s): Number of patients treated with PD-1/PD-L1 inhibitors 140. Number of patients who had thyroid dysfunction N=62 (44%). Male: Female 32:30. Median age 66 years (range 35-80). Histology: 37 Adenocarcinoma, 20 squamous cell carcinoma, 2 small cell lung cancer and 3 pleomorphic/poorly differentiated. PD-1/PD-L1 drugs administered: Durvalumab 1, Nivolumab 1, Atezolizumab 8 and Pembrolizumab 52. Biochemical/subclinical hyperthyroidism was observed in 25/62 (40%), hypothyroidism 31/62 (50%) and hyperthyroidism followed by hypothyroidism in 6/62 (10%). No specific thyroid dysfunction related symptoms/signs were noted. 10 patients were treated with levothyroxine. The time kinetics of thyroid dysfunction are shown in Fig. 1. Thyroid dysfunction most commonly occurred in the first 3 cycles (56%) and 85% of the events occurred in the first 12 cycles. 5% of the patients experienced thyroid dysfunction after completion of PD-1/PD-L1 treatment programme. No deaths were attributable to thyroid dysfunction. [Figure presented] Conclusion(s): In our cohort treated with PD-1/PD-L1 inhibitors, thyroid dysfunction was the most common IrAE. Thyroid IrAE is characteristically early with majority of the events occurring within the first 12 cycles. There was no gender predilection. All thyroid IrAE were subclinical and only 10% had thyroxine supplementation. The cohort is too small for any exploratory hypotheses. Disclosure: No significant relationships.