BACKGROUND: While there is increasing recognition of the morbidity of cardiovascular disease in cancer survivors, including accelerated atherosclerosis following thoracic radiotherapy, patients are frequently under-optimized for cardiovascular risk. METHODS: In this prospective single-arm cohort pilot study, patients were treated with high-dose thoracic radiotherapy and had early consultation with cardio-oncology. Twenty patients were enrolled. The primary endpoint was adherence to cardio-oncology consultation. Secondary endpoints were cardiovascular medication intervention rate and patient-reported intervention perspectives. Clonal hematopoiesis of indeterminate potential, a major cardiovascular risk marker enriched in patients with cancer and induced by radiation exposure, was measured as an exploratory endpoint. RESULTS: The cohort median age is 71 years. Most patients are female (13/20), have primary lung or esophageal carcinoma (16/20), and 7/20 have pre-existing cardiovascular disease. We show that cardio-oncology consultation adherence is high (19/20) and results in cardiovascular medication optimization changes in most patients (12/19), most commonly to initiate or intensify statin therapy (8/12). 8/12 patients with a primary cardiologist prior to enrollment have medication changes recommended. Most (12/17) participants are glad to learn about their heart health during cancer treatment. Clonal hematopoiesis is detectable prior to treatment in 8/20 patients and three develop new variants after treatment (1/3 de novo). CONCLUSIONS: We observe that early cardio-oncology consultation is feasible, leads to cardiovascular medication optimization in the majority (>
60%) of participants, most commonly to initiate or intensify statin therapy. New clonal hematopoiesis variants are detectable early after radiotherapy and the impact on post-treatment cardiovascular risk is worthy of further study.