LAUSR

Background: CDK4-6 inhibitors are now considered the standard of care for advanced ER-positive HER2-negative advanced breast cancer (ABC) in combination with endocrine therapy (ET). During the first wave of the COVID-19 pandemic, clinicians were uncertain what impact CDK4-6 inhibitor-induced immunosuppression may have on the risk of contracting COVID-19 or the severity of infection. Some clinicians pre-emptively reduced doses, altered schedules, or even withheld treatment, continuing ET alone. There is currently no evidence that CDK4-6 inhibitors increase the risk or severity of COVID-19 infection, although there have reports of protracted illness. We describe our experience of 203 patients receiving CDK4-6 inhibitors during the first wave and demonstrate the safety of continuing treatment during this period. Methods: Epidemiological and clinical data were collected prospectively for patients at the Royal Marsden Hospital (RMH) and one network hospital with a ER-positive HER2-negative ABC that were receiving a CDK4-6 inhibitor between April 1st and June 30th 2020. Results: 200 patients received a CDK4-6 inhibitor in combination with ET, of which of 65/200 fulfilled local criteria to be screened with COVID-19 PCR testing and 6/65 were swab-positive. Two patients required hospital admission but there were no ICU admissions or COVID-19-associated deaths. Only 12 patients (6%) had treatment adjustments in the form of dose reduction (3/12), regime adjustment (2/12), or temporary interruption (7/12). In 9/12 cases this was a prophylactic measure due to additional risk factors;age (n=1), co-morbidities(n=3), patient choice (n=1) or overall concerns (n=4) to reduce the risk of contracting COVID-19. Results on dispensing >2 cycles at a time, telephone clinics, deferred CT scans and complications relating due to remote monitoring will also be reported. Conclusions: Based on this snapshot during the first wave of the COVID-19 pandemic, we conclude that continuation of CDK4-6 inhibitors appears safe. This project is helping to drive a UK-wide review of CDK4-6 inhibitor treatment continuation, adjustment during the pandemic, assessing the risk of acquiring clinically severe COVID-19 infection, and subsequent cancer-related outcomes for these patients. Legal entity responsible for the study: The authors. Funding: Has not received any funding. Disclosure: S.R.D. Johnston: Advisory/Consultancy: Eli Lilly;Advisory/Consultancy, Speaker Bureau/Expert testimony: AstraZeneca;Advisory/Consultancy, Research grant/Funding (institution): Puma Biotechnology;Advisory/Consultancy, Speaker Bureau/Expert testimony, Research grant/Funding (institution): Pfizer;Advisory/Consultancy, Speaker Bureau/Expert testimony: Novartis;Speaker Bureau/Expert testimony: Eisai;Research grant/Funding (institution), Clinical Trials: Roche/Genentech;Research grant/Funding (institution), Clinical Trials: Eli Lilly;Research grant/Funding (institution), Clinical Trials: Pfizer;Research grant/Funding (institution), Clinical Trials: AstraZeneca;Research grant/Funding (institution), Clinical Trials: Novartis;Research grant/Funding (institution), Laboratory studies: Pfizer;Research grant/Funding (institution), Laboratory studies: Puma Biotechnology. A. Okines: Research grant/Funding (self): Pfizer;Honoraria (self): Leo Pharma;Speaker Bureau/Expert testimony: Seagen;Advisory/Consultancy: Roche;Research grant/Funding (self): Roche;Honoraria (self): AstraZeneca;Advisory/Consultancy: Seagen. S. McGrath: Speaker Bureau/Expert testimony: Pfizer. All other authors have declared no conflicts of interest.