Background: The COVID-19 pandemic is negatively affecting patient enrollment, therapy administration, and patient visits in breast cancer clinical trials worldwide. COVID-19 may have a lasting impact on how clinical trials are conducted, and guidelines are necessary to inform trial design and patient safety. While many groups and journals have recently published guidelines, including NCCN, ESMO, IQVIA, and Lancet Oncology, there is no consensus on how to treat patients in the current environment. Understanding and quantifying the impact of the pandemic on clinical study sites will help inform the rational development of a consensus approach. The goal of this survey was to gather site-level data on the impact of COVID-19 from clinical sites participating in the POLARIS study (NCT03280303), an ongoing, prospective, real-world, noninterventional study in patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer receiving palbociclib plus endocrine therapy. Methods: Two rounds of questionnaires were sent to investigators at POLARIS study sites: 1 via email March 26-27, 2020, and 1 via telephone from April 30-May 20, 2020. The questions on COVID-19 impact and management are shown in the Table. Results: Eighty of 122 POLARIS study sites contacted responded to the March questionnaire, and 86 responded to the April-May questionnaire. In March, 33% (26/80) of the surveyed population were working predominantly remotely, 26% (21/80) were working both onsite and remotely, and 31% (25/80) were working onsite. Approximately 24% of sites reported delayed data entry. The option of telemedicine or office visits was offered to subjects at approximately 73% (58/80) of sites, and 11% (9/80) of sites were restricted to telemedicine visits. In April-May, 36% (31/86) of respondents reported an impact on study management and 64% (55/86) reported no impact. Approximately 94% (81/86) of surveyed sites felt they were able to maintain clinical studies despite the challenges due to COVID-19, and 79% (68/86) of sites had the option for telemedicine and/or office visits, while 18% (16/86) had no telemedicine alternative. In April-May, 38% of sites reported an impact on patient visits. Conclusion: Although these findings must be interpreted with caution due to the limitations of survey studies, the results suggest that approximately 1/3 of the study sites will experience an impact on their responsiveness to correspondence, timely data entry, and subject management due to the COVID-19 pandemic. Telemedicine may be used to mitigate the effect of the pandemic on clinical trial execution. Pfizer (NCT03280303) Citation Format: Debu Tripathy, Joanne L Blum, Gabrielle Rocque, J. Daniel Cuevas, Jennifer Specht, Steven Corso, Jawad E Francis, Stephanie Mendez, Veneta Pope, Joseph Cappelleri, Yao Wang. Impact of COVID-19 on study sites: Survey analysis from the noninterventional POLARIS study [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr SS2-10.