CT Lung Cancer Screening

In June 2011, the New England Journal of Medicine published results from the National Lung Cancer Screening Trial (NLST) that showed a 20% mortality reduction in a high-risk population who had been screened using low-dose CT as compared to a control group screened using chest radiography. NLST is the first lung cancer screening trial to demonstrate such a mortality benefit.

In October 2011, the National Comprehensive Cancer Network (NCCN) issued guidelines recommending low-dose CT screening for lung cancer.

Stanford Medicine Imaging will be offering this screening test to patients who meet the criteria used either in NLST or recommended in the NCCN guidelines. (See Exam Eligibility)

Radiation dose reduction and optimization

At Stanford Medicine Imaging, we understand that radiation exposure is a concern to referring physicians and patients. We are committed to reducing radiation exposure and follow radiation safety principles. CT lung cancer screening will be a low-dose CT exam, with a radiation dose of approximately 1.5 mSv (millisieverts), equivalent to approximately half of the naturally occurring background radiation that a person receives for one year at sea level. This exam does not require intravenous contrast. 

False positives

Left: 65 year-old woman

Right: Eight months later

Over the period that NLST participants were screened, approximately 40% of individuals had a positive CT result, usually consisting of small indeterminate pulmonary nodules considered suspicious for lung cancer, on at least one of the three annual tests. These findings required diagnostic follow-up, mostly with further imaging, and in some cases invasive procedures such as bronchoscopy or percutaneous biopsy. Of these initial findings, 96.4% were false positives.

The rate of complication during follow-up of the CT group was 1.4%. The rate of major complication was 0.06% in the false positive group and 11.2% in those with lung cancer. Of the cancers detected, most were adenocarcinomas, many of which were detected at stage I or II. The death rate from any cause in the CT screening group was reduced by 6.7%, compared to the radiography group. One death from lung cancer was prevented per 320 participants in screening.

Suspicious nodules

If a suspicious nodule is identified on a screening CT, patients and their referring physician can be provided a list of Stanford physicians with expertise in the further evaluation and management of such nodules – including pulmonologists and thoracic surgeons. The patient may then make an appointment with one of these individuals to determine any appropriate additional steps to be taken.


Currently, CT screening for lung cancer is not covered by insurance. Eligible patients must be referred by a physician. Active smokers undergoing screening CT should enter a smoking cessation program. Screening is not an alternative to smoking cessation.