Abstract Background: Patients with lung cancer are at high risk from COVID19. Efforts are ongoing to limit exposure of patients with lung cancer to the health care system. As a result, the COVID19 pandemic has drastically changed cancer care, but the extent and type of these changes are unknown. The goal of this study was to evaluate the changes in lung cancer treatment during the peak of the COVID19 pandemic. Methods: We prospectively assessed the cancer management plan of all patients seen in the thoracic oncology clinic at our center between March 2 and April 30, 2020. Inclusion criteria for this study were a diagnosis of either non-small cell lung cancer or small-cell lung cancer. Those who had a diagnosis of COVID19 were excluded from the study. Primary endpoints were to describe the extent of changes in the cancer treatment plan and qualify the types of changes observed. Results: A total of N=289 patients were evaluated between March 2 and April 30, 2020. N=14 patients were excluded due to presence of other tumor histology, and 2 patients were COVID19-positive. Among the 275 patients included, median age was 68 and 47% were male. Among the 238 patients (86.5%) with non-small cell lung cancer, 172 (62.5%) had advanced disease. Among the 37 patients (13.5%) with small-cell lung cancer, 11 (4%) had extensive disease. 211 were receiving active treatment (76.5%), with 35.1% on chemotherapy, 21.8% on oral agents, 31.8% on immune checkpoint inhibitors, and 11.4% on combination therapy. 121 (57%) of patients experienced at least one change in their lung cancer treatment plan as a direct result of the COVID19 pandemic, with 19 (9.0%) patients experiencing more than one change. The majority of changes encompassed delay or cessation of palliative treatment, N=48 (39.7%), N=18 (14.9%), respectively. Mean time to resumption of palliative treatment was 36 days, and 3% of patients stopped palliative treatment permanently as a direct result of the pandemic. Changes in dosing and schedule occurred in N=32 (26.4%), which included changing pembrolizumab to q 6 weeks or durvalumab to q 4 weeks. A minority of patients experienced delays in adjuvant chemotherapy administration (N=3 (2.5%)) with a mean delay of 42 days. Lastly, 6.6% of patients experienced deferrals or cancellations of surveillance scans or visits due to COVID19. Other changes included the decision not to pursue palliative chemotherapy. Conclusion: Our study demonstrated that a significant proportion (57%) of patients experienced changes in their lung cancer management plan as a direct result of the COVID19 pandemic. Given the preliminary findings that active cancer treatment is not associated with increased complications from COVID19, lung cancer treatments and surveillance visits should continue to proceed with caution, and oncology care providers should continue to carefully proceed with evidence-based care in lung cancer. Citation Format: Suzanne Kazandjian, Nathaniel Bouganim, Arielle Elkrief. Changes in lung cancer treatment as a result of the COVID19 pandemic: A prospective observational study [abstract]. In: Proceedings of the AACR Virtual Meeting: COVID-19 and Cancer; 2020 Jul 20-22. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(18_Suppl):Abstract nr PO-010.