Background: Malpractice cases may contain valuable information to inform safety improvement efforts in cancer care. No analyses of malpractice cases have been published focusing on medical oncologists as the primary defendant. The recent development of a new safety incident taxonomy for medical oncology enabled us to classify malpractice cases and identify patient safety improvements.¹. Methods: We conducted a qualitative analysis of case vignettes naming medical oncologists as the primary defendant. Case vignettes were obtained from CRICO’s Candello database. Of 452 cases against medical oncologists, a random sample of 100 cases was selected. Cases were coded for the type of safety incident, and whether a system solution could plausibly reduce the risk of a future event. Coding was performed by 3 physicians with experience caring for patients with cancer. Two reviewers reviewed each case; discrepancies were resolved by the third reviewer. Results: Ninety-nine cases were included in the final analysis; 1 was determined to be misassigned to medical oncology as the primary defendant when the case vignette was entirely about radiation oncology treatment and side effects. The most frequent cancer types were breast (16%), acute leukemia (9%), aggressive lymphoma (8%), and gynecologic malignancies (7%). The most common safety incidents identified were provider clinical management errors (41%), adverse drug reactions (20%), relational issues among providers, patients, and other healthcare staff (13%), and prescriber ordering errors (6%). 47 case vignettes described safety incidents that might have been prevented by a systems intervention. The most common interventions were “tumor board or expert review of rare or uncertain cases” (19%), “pharmacist review for safe prescribing of chemotherapy” (17%), “cancer navigator for appointment scheduling in high-risk settings” (9%), “closed loop communication with radiology” (6%), and “electronic patient portal access to all test results” (6%). Conclusions: Using a new medical oncology-focused incident coding taxonomy, we were able to classify all 99 malpractice cases. Human factors issues accounted for the majority of claims. We determined that more comprehensive use of existing improvement interventions might substantially reduce the risk of future events. ¹ Jacobson, J. et al. Development of a taxonomy for characterizing medical oncology-related patient safety and quality incidents: A novel approach. BMJ Open Quality. [Manuscript in press]. Accepted June 10, 2022. DOI 10.1136/bmjoq-2022-001828.R2.