Background: Nowadays, the (SARS-CoV-2 or COVID19) is an ongoing worldwide pandemic. Substantial changes in the management of metastatic breast cancer patients have been required worldwide in response to the COVID-19 pandemic. This study is focused to evaluate the adoption of the new guidelines for MBC patients who had been treated with CDK4/6 inhibitors. Methods: We had 2 groups of Metastatic BC ER+ HER2- patients who started the CDK4/6 inhibitors during 2 periods, from 1st June 2019 to 30th June 2020 and from 30th June 2020 to 31th October 2020, this includes 45 and 42 patients respectively. The international ESMO COVID-19 & national (NICE) guidelines were implemented. All changes to treatment were conducted in view of delay, omission or reduction of the dose to assess what were the most frequent implications of these changes. Toxicities assessed based on CTCAE 4.0. Data was compared between first and second wave of the pandemic in the UK. The evidence reported reflects the experience matured at our Trust. Results: Two groups of total of 87 patients were enrolled in the study who started treatment with CDK4/6 inhibitors during both waves of the COVID-19 pandemic. Comparison of the 2 groups revealed that 95.3% of patients were females. 45 and 42 patients had Palbociclib and abemaciclib. 13 of them aged > 75 years old. In the first wave: 33.3% had dose reduction. 8 Patients had progression. 15.6% had toxicity required admission. 57.8% continued the treatment without significant toxicities. In the second wave: 52.4% had dose reduction, of those 38.1% due to toxicities. DP in 4 patients. 23.8% had toxicity admission. 88.1% continued the treatment with non significant toxicities. The mortality was 4% in second group in comparison to 11.9% in the first one. No Covid-19 related death reported. Conclusions: The data comparing the oncological outcomes in patients who had their treatment during both waves of the pandemic confirmed the safety of the delivery of the CDK4/6 inhibitors during COVID-19. The Dose reduction has led to more tolerability and does not affect the efficacy. The neutropenia associated with CDK4/6 inhibitors is unlikely to increase the risk of Covid-19 infection. Legal entity responsible for the study: The authors. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.
243P CDK4/6 inhibitors in clinical practice during COVID-19 pandemic: Comparative analysis of the clinical impact of the pandemic for metastatic breast cancer patients during first and second waves in the UK