4CPS-085 Evaluation of the incidence of hepatitis B virus reactivation in patients treated with pembrolizumab

<h3>Background and Importance</h3> Recent studies have found that patients with anti PD-L1 treatment, as in the case of pembrolizumab, the incidence of hepatitis B virus reactivation has been increased in those patients with positive HbcAb (hepatitis B core antibody), recommending the use of prophylaxis to avoid it. <h3>Aim and Objectives</h3> To evaluate the incidence of hepatitis B virus reactivation and the use of prophylaxis under real conditions in patients on pembrolizumab treatment. <h3>Material and Methods</h3> Retrospective observational study between January 2014 and July 2024. Patients over 18 years of age who initiated treatment with pembrolizumab were included. Demographic variables such as sex, age, weight, and height were collected. The clinical variables were HbsAb (hepatitis B surface antigen antibody), HbcAb, were collected in a previous period of 6 months before the start, during and up to 1 year after the end of treatment, the data were obtained from the patients‘ medical records. Serology interpretation: <h3>Results</h3> The study included 263 patients, 174 men (64%) and 89 women (34%), with a mean age of 64.7 + 11 years, mean weight of 69 + 14 kg, mean height of 166 + 10 cm. Previous to treatment, 98 (37%) patients underwent hepatitis B serology obtaining: There were 18 patients (18%) with a positive serology for HbsAb and HbcAb indicating that the infection has passed and the virus can be reactivated. Three patients (3%) with positive HbcAb alone indicate that they may be infected, and nine patients (9%) with positive HbsAb alone indicate that they are vaccinated. <h3>Conclusion and Relevance</h3> The results obtained in this study show that reactivation of the virus did not occur in any patient, and despite the recommendations, in no case was prophylaxis prescribed to prevent it. Hepatitis B serology was not performed in 165 patients (63%), which may pose a risk to the patient‘s health. <h3>References and/or Acknowledgements</h3> Ding Z-N, Meng G-X, Xue J-S, Yan L-J, Liu H, Yan Y-C, <i>et al</i>. Hepatitis B virus reactivation in patients undergoing immune checkpoint inhibition: systematic review with meta-analysis. <i>J Cancer Res Clin Oncol</i>. 2023;<b>149</b>(5):1993–2008 <h3>Conflict of Interest</h3> No conflict of interest