Association between immunotherapy and hypothyroidism in a Latin American population: An analytical study of cases and controls from 2019 to 2023.

Abstract

e24135 Background: In different clinical studies worldwide, the use of immunotherapy has been related to the development of hypothyroidism; However, there is no data on this association in Latin American population. Methods: An analytical observational case-control study conducted in a 3-year follow-up cohort at an oncology institute of cancer patients treated with immunotherapy who developed hypothyroidism in Colombia. The aim of the study was to evaluate the development of new hypothyroidism cases after immunotherapy. Cases and controls were randomized in a ratio of 1:3. A multivariate analysis was performed to identify risk factors for developing hypothyroidism and an inferential analysis was performed over time between levothyroxine dose vs TSH levels. Results: 112 patients were included, 57% men and 42% women with a mean age of 63 years. 21% developed hypothyroidism after immunotherapy, while 12% presented with thyrotoxicosis as first alteration and 9% with central hypothyroidism. During the first semester 54% of patients developed hypothyroidism, 84% in the first year and 100% at 2 years . Pembrolizumab and nivolumab were used most frequently with 58% and 29% respectively developing hypothyroidism. The most common underlying pathology was lung cancer with 33% and kidney at 38%. In the multivariate analysis, female were found as a protective factor compared to men (OR:0.10 CI: 0.05-0.63 95% p = 0.02), and the use of pembrolizumab was associated with a higher risk trend, but this result was not statistically significant (OR:2.49 CI: 0.5-2.7 p = 0.2). The average initial dose of levothyroxine was 1.4 mcg/kg, at 3 months of 1.2 mcg/kg and 6 months of 0.82 mcg/kg. Average TSH levels at diagnosis were 23.3, uUI/ml, achieving target values for 100% of patients after 9 months of substitution. After two years of follow-up, patients continued with an average dose of levothyroxine of 0.8 mcg/kg. Conclusions: The incidence of hypothyroidism in our population is similar to that reported worldwide. Male patients who start immunotherapy should have their thyroid profile monitored strictly given that they present a higher risk. Additionally, monthly monitoring of the thyroid profile should be done within the first year. In Latin American population, more conservative initial doses of levothyroxine (1.0 - 1.1 mcg/kg) could be used and titrated.