A Claire Watkins

MD, MS

Stanford University

Assistant Clinical Professor

NLST (Learn more about this study)

NLST-638

Feb 19, 2020

Evaluation of Thoracic Aortic Aneurysm Mortality with Low-Dose Computed Tomographic Screening.

Thoracic aortic aneurysms (TAA) are commonly diagnosed when acute, catastrophic complication occurs. Surgical therapy for incidentally diagnosed, asymptomatic thoracic aortic disease carries significantly better outcomes compared to acute aortic rupture or dissection. The opportunity to diagnose and treat TAA prior to development of symptoms or complication would greatly reduce morbidity and mortality from the disease. Clinical screening for aortic disease has used varied methods and presented equivocal results. The most recent guidelines from the American Heart Association recommend screening for thoracic aortic disease through medical history only.
The US Preventive Services Task Force recommends one-time ultrasound screening for abdominal aortic aneurysm (AAA) in males age 65-74 years old who have ever smoked. Similar one-time screening recommendations are in practice in the United Kingdom and Sweden. A single ultrasound screening for AAA has been shown to half the mortality rate due to AAA in men aged 65-74 years. However, nearly half of deaths from ruptured abdominal aneurysms in the United States occur in patients outside these limited screening criteria. Additionally, screening has not been extended to thoracic aortic disease.
Established risk factors for TAA include male sex, prior and active smoking, hypertension, emphysema, and familial history. Lung cancer and TAA share many of these same risk factors and can both be detected on a chest X-ray or non-contrast, low-dose CT scan. Through analysis of existing imaging studies, we hope to define the incidence of thoracic aortic disease among lung cancer screening patients, those aged 55-75 years, with at least 30 pack year smoking history and who actively smoke or have quit within the past 15 years. Clinical data available in the National Lung Cancer Screening (NCLS) trial includes many variables relevant to this study, including significant cardiovascular abnormalities found on imaging, participant demographics and risk factors, long-term mortality and cause of death, as well as non-cancer ICD-10 diagnosis codes. Our primary outcomes will be thoracic aortic disease detected on lung cancer screening imaging and cardiovascular mortality among those with and without detected aortic disease.
Our research group includes 3 aortic surgeons, a cardiovascular radiologist, statistician and research information technologist. We have the resources and institutional support to perform an analysis similar to that done by the NLCS Trial research team. A positive result in this data may justify a larger screening trial targeted at thoracic aortic disease, while a negative result will offer further insight to the topic. The ability to identify a thoracic aortic disease prior to aortic catastrophe would not only prevent aortic-related mortality but would decrease complications and improve the quality of life for aortic patients. The NLCS trial was a monumental improvement in the care of lung cancer patients. We hope to use this data to similarly advance the care of aortic patients.