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Approximately 77,000 participants were randomized into the intervention arm. Each was expected to comply with two flexible sigmoidoscopies (FSGs): one at baseline (T0 FSG) and another 3 or 5 years later (T3/5 FSG). The T3 FSG was expected for participants randomized prior to October 1994. The T5 FSG was expected for those randomized on/after December 7th, 1995. For randomization between these dates, T3 FSG was scheduled, but if that screen was missed, T5 FSG was offered. Overall, about 107,000 screening FSGs (65,000 at baseline and 42,000 at T3 or T5) were conducted among 67,000 participants who complied with at least one screen. 39,000 participants had FSGs both at baseline and at the return visit.

FSG cancer screening results are contained in the data as a summarized/qualitative result (i.e., negative, abnormal suspicious, abnormal non-suspicious, inadequate). Additional findings (e.g., lesion size, number of lesions) are also captured.

In the data, an FSG result in a study year is almost always given as the result of one FSG done during one visit to the screening center. However, there are some exceptions. For one, about 3700 FSGs had an accompanying quality assurance (QA) FSG. For these screens, if the QA result was more severe than that of the scheduled protocol screen (severity: abnormal suspicious > abnormal non-suspicious > negative > inadequate) then the FSG result for that year is that of the QA screen. This occurred in about 230 of the 3700 FSGs with QA. Another exception includes 660 inadequate FSGs reattempted at a later visit that same year. In about 550 participants (83%), a reattempted FSG yielded an adequate result, and so the FSG result for that year is that adequate result.

For most purposes, screening data can be obtained within the Colorectal dataset. Additional details are contained within the Colorectal Screening dataset (one record per screening study year per person) or the Colorectal Screening Abnormalities dataset (one record per lesion per screen per person).

Summary Available Data
  • Intervention arm only
  • Data summarized for each study year
  • FSG data for T0 and T3/5 (T5 exams introduced in 1995)
  • FSG data collected on FSG (Flexible Sigmoidoscopy Screening Examination) forms:
  • Screening protocol group
  • Days from randomization to screens
  • FSG results by study year
  • Count of lesions seen
  • Lesion location and size
  • Available in screening and abnormality datasets:
    • QA / Protocol screens as separate data
    • Multiple visits to screening center as separate data
    • Examiner ID
    • Reason for inadequate FSG
    • Other FSG findings