Introduction A coronary artery calcium (CAC) CT scan can identify calcified plaque and predict risk of future cardiac events. Cancer survivors undergoing thoracic radiotherapy routinely undergo a planning CT scan, which presents a unique opportunity to use already obtained medical imaging to identify those at the highest risk of cardiac events. While radiation therapy is an important modality for many cancer treatments, radiation dose to the heart in thoracic radiotherapy leads to cardiotoxicity and may accelerate pre-existing atherosclerosis. The primary aims of this study are to investigate the feasibility of using CAC scores calculated on thoracic radiotherapy planning CT scans to identify a subset of cancer survivors at an increased risk of future cardiac events, and to establish and evaluate a referral pathway for assessment and management in a cardio-oncology clinic. An optional substudy aims to investigate using abdominal aortic calcification (AAC) as a practical, low-radiation alternative to CAC to evaluate and monitor vascular health. Methods and analysis This is an observational, prospective study in a minimum of 100 cancer survivors commencing radiotherapy. Participants will have CAC scored from thoracic radiotherapy planning CT scans. Those identified as high risk (CAC score>0) will be referred to a cardio-oncology clinic. Feasibility, determined by adherence to the recommended pathway, and impact on quality of life and anxiety measured via questionnaire, will be assessed. Participants in Western Australia will be invited to participate in a 12-month observational pilot substudy, investigating lifestyle behaviours and the use of a dual-energy X-ray absorptiometry machine to measure musculoskeletal health and AAC. Ethics and dissemination Ethics approval has been obtained from St Vincent's Hospital, Sydney (Project number 2021/ETH11847), GenesisCare and Edith Cowan University (2022-03326-DALLAVIA). Study results will be reported in peer-reviewed academic journals, at scientific conferences, and at clinical forums, irrespective of the results observed. Trial registration number ACTRN12621001343897.