5PSQ-146 ‘Real life’ effectiveness and safety assessment of foscarnet

Background and importance Cytomegalovirus (CMV) infection is an important cause of mortality, especially in haematological patients. Foscarnet has been used to treat ganciclovir resistant CMV infections. Only a few studies assessing safety and effectiveness of foscarnet have been reported so far. Aim and objectives To evaluate the effectiveness and safety of foscarnet in the treatment of CMV infection in a third level hospital. Material and methods A retrospective observational study was conducted in patients who received foscarnet as treatment for CMV viraemia from January 2018 to April 2020. Variables collected were: age, sex, pathology, time of treatment, pattern, basal (start of foscarnet) and final (when foscarnet was suspended) viral load (VL), basal and nadir glomerular filtrate (GF) and metabolic toxicity (basal and nadir serum electrolytes). The results were obtained from the electronic history and prescription software (Farmatools). Results 39 patients, 22 men, were included, and mean age was 55.8±14.9 years (26–82). 71.8% were haematological patients, of whom 41.0% had received bone marrow transplantation. Mean time in treatment was 11±6.6 days (1–27). The dosage pattern was 90 mg/kg/12 hours in 69.2%. 23.0% started treatment as prophylaxis with undetectable VL. In the remaining patients, median basal VL was 1135 IU/mL (3.34–65400), final VL was undetectable in 46.1% and in those who did not negatively affect the median final VL was 215 IU/mL (34.5–6690). Mean reduction in VL was 90.4±17.9% (18–100). There was a 64.1% reduction in GF (mean reduction of 25.6±21.2% and 36.7±22.0% over >65 years). Metabolic toxicity, according to the CTCAE classification (V.4.0), hypokalaemia (grade 1 in 10.2% patients, grades 2 and 3 in 33.3%, grade 4 in 5.1% and the rest were not altered) and hypophosphataemia (grade 1 in 10.2%, grades 2 and 3 in 33.3% and grade 4 in 2.5%) were studied. In addition, hypomagnesaemia (grade 1 in 12.8%) and hypocalcaemia (grade 2 in 28.2% and grade 3 in 33.3%) were also observed. 41.0% of patients died during or immediately after treatment with foscarnet. Their average age was 61±14.4 (27–82) years and 81.2% presented haematological pathologies. Conclusion and relevance Despite the high mortality observed, foscarnet effectively reduced viraemia due to CMV infection, with a high rate of viral negativisation. Further studies are needed to extend the toxicity data and improve the quality of care. References and/or acknowledgements Conflict of interest No conflict of interest