5PSQ-038 Safety of cyclin dependent kinase inhibitors in the treatment of breast cancer with positive hormonal receptors and negative human epidermal growth factor receptor 2

Background and importance Cyclin dependent kinase (CDK) inhibitors are an innovative therapeutic target for the treatment of locally advanced or metastatic breast cancer with positive hormonal receptors (HR) and negative human epidermal growth factor receptor 2 (HER2). Some adverse reactions have been reported than can decrease a patient’s functional status or even lead to suspension of this line of therapy. Aim and objectives To analyse the frequency of the main drug adverse reactions described for the different CDK inhibitors used for the treatment of patients with locally advanced or metastatic breast cancer in a third level hospital. Material and methods A retrospective observational study was performed in patients who had started treatment with a CDK inhibitor between 1 June 2018 and 30 September 2019. Demographic and clinical features were obtained from the electronic patient clinical history (DIRAYA) and the electronic prescription programme (PRISMA) and recorded in an Excel worksheet. Adverse reactions recorded were diarrhoea, digestive disturbances, mucositis, asthenia, neutropenia, leucopenia, anaemia, thrombopenia, nausea and vomiting, anorexia and elevated transaminase blood levels. Results Forty-two patients were found (41 women): 18 received palbociclib, 15 received ribociclib and 9 received abemaciclib. Average age was 56.8±10.0 years. Average length of treatment was 135.4±92.5 days, with an average number of cycles of 3.8±3.4. In 19% of patients, treatment was discontinued due to death (50%), progression (25%) or toxicity (25%). The most frequent drug adverse reactions were neutropenia (52.4% of patients), asthenia (40.5%) and anaemia (26.2%), followed by thrombopenia (19%), nausea and vomiting (19%), diarrhoea (16.7%) and elevated transaminase levels (9.5%). In some cases, digestive disturbances (4.8%), mucositis (4.8%), anorexia (2.3%) and leucopenia (2.3%) were reported. Between the different drugs, diarrhoea and asthenia were the most prevalent adverse reactions in patients receiving abemaciclib (55.6% in each), and neutropenia in those receiving palbociclib (66.7%) and ribociclib (53.3%). Conclusion and relevance According to our results, the main adverse reactions should have been expected, in accordance with the drug data sheets. Knowledge of possible RAM allows us to improve patient safety. Nevertheless, it is necessary to expand the study to have more information on the frequency of these reactions during long term treatments. References and/or acknowledgements No conflict of interest.