Peripheral Vascular Disease as a Clinical Trigger for Opportunistic Lung Cancer Screening Referral: An Implementation Study

The study aims to determine whether patients with peripheral vascular disease who attend the vascular clinics are eligible for lung cancer screening. This is because long-term cigarette smoking exposure is associated with peripheral vascular disease, and smoking is again the main risk factor for lung cancer.

These clinical encounters provide a potential opportunity to identify individuals who may qualify for lung cancer screening but are not routinely assessed for screening eligibility. Integrating systematic screening eligibility assessment within vascular clinics could therefore represent an effective strategy for identifying high-risk individuals and improving referral for lung cancer screening.

Additionally, peripheral arterial disease is commonly diagnosed using the ankle-brachial index (ABI), a non-invasive measure that compares systolic blood pressure between the ankle and brachial arteries. An ABI value below 0.90 is widely recognised as diagnostic of peripheral arterial disease and reflects the presence of systemic atherosclerosis.

ABI has been increasingly recognized as a marker of cumulative exposure to cardiovascular risk factors, particularly long-term tobacco smoking. Tobacco smoking contributes to endothelial dysfunction, chronic inflammation, and atherosclerotic plaque formation, mechanisms that are also implicated in lung carcinogenesis.

Because both lung cancer and peripheral vascular disease share major risk factors, ABI may serve as a clinical proxy indicator of cumulative smoking-related vascular damage. Individuals with lower ABI values may therefore represent a subgroup with higher cumulative tobacco exposure and potentially elevated lung cancer risk.

Evaluating the association between ABI severity categories and lung cancer diagnosis may provide insights into whether vascular disease severity could help identify individuals who may benefit from targeted screening interventions. If an association is observed, ABI could potentially be used as a simple, routinely measured clinical indicator to prompt lung cancer screening assessment in vascular care settings.

Therefore, this study will determine the proportion of the vascular disease patients who fall under the high-risk group for lung cancer screening and refer them to low-dose CT scan and follow-up them for the results and the adherence.