All participants were expected to receive three annual screening exams (T0, T1, T2) for lung cancer. Participants were randomized into two study arms at the time of enrollment, with each arm receiving a different type of screening exam. Half of NLST participants were randomized to receive low-dose helical (spiral) CT exams, and half to receive chest radiograph (CXR) exams.

Radiologists were required to review the images in two ways: looking at the image without reference to historical images (isolation read), and then looking at the image again with reference to historical images (comparison read). An exam was considered positive (i.e., suspicious for lung cancer) if the radiologist observed a non-calcified nodule or mass with diameter ≥ 4 mm (always positive) or if other abnormalities appeared suspicious for lung cancer (in the radiologist's judgment). For the T1 and T2 comparison reads, the radiologist was required to record whether a positive exam displayed any significant change relative to prior images. The radiologist had discretion at T2 to classify as negative an exam that met the criteria for a positive exam but displayed no significant change relative to the previous two exams. The comparison read yielded the official screening result reported to participants and used to determine follow-up recommendations.

After reviewing the screening images, radiologists provided recommendations for follow-up procedures.

Summary

• ~75,000 CT exams, ~73,500 CXR exams
• Comparison read is the official result
• Data contained in several datasets
  • Participant dataset: both arms
  • SCT Screening and XRY screening datasets: one record per screening exam received
  • SCT Abnormalities and XRY Abnormalities datasets: one record per abnormality observed on either the isolation or comparison read
  • SCT Comparison Read Abnormalities and XRY Comparison Read Abnormalities datasets: one record per abnormality noted on comparison read (all significant abnormalities from current image, whether or not they were also visible in older images)
• Spiral CT data were collected on the following forms:
  • LSS SCT (PDF - 171 KB)
  • ACRIN C2 (ACRIN NLST CRF Set)
  • ACRIN I9 (ACRIN NLST CRF Set)
• Chest x-ray data were collected on the following forms:
  • LSS XRY (PDF - 189 KB)
  • ACRIN DR (ACRIN NLST CRF Set)
  • ACRIN I8 (ACRIN NLST CRF Set)

Available Data

• In participant dataset
  • Screening result (isolation and comparison reads)
  • Days from randomization to screen
• In screening datasets
  • Technical parameters
  • Reader ID
  • Recommendations for diagnostic follow-up
• In abnormality datasets
  • Type of abnormality
  • Characteristics of non-calcified nodules / masses
• In comparison abnormality datasets
  • Type of abnormality
  • Changes since previous historical image
• CT images may be obtained as described on the Images page