In the material that follows, we list cancers in alphabetical order; information from the USPSTF appears before that from the Canadian TF. For the USPSTF, the entries below come from the Web site of AHRQ, which supports the current USPSTF; the specific URLs are not listed here, but the general one is http://www.ahrq.gov/clinic/cps3dix.htm#cancer (accessed May 4, 2004). Harris et al. (2001) present more information on USPSTF methods. The general URL for material from the Canadian TF is http://www.ctfphc.org/ (accessed May 4, 2004).
The USPSTF uses specific grades for quality of evidence and recommendations. The definitions for the grades are noted below (http://www.ahrq.gov/clinic/3rduspstf/ratings.htm#irec, accessed May 4, 2004), and the recommendations themselves follow. After them is the older grading system used by the Canadian TF.
The USPSTF assigns one of three to the overall evidence for a service: good, fair, or poor:
“Good: Evidence includes consistent results from well-designed, well-conducted studies in representative populations that directly assess effects on health outcomes.
“Fair: Evidence is sufficient to determine effects on health outcomes, but the strength of the evidence is limited by the number, quality, or consistency of the individual studies, generalizability to routine practice, or indirect nature of the evidence on health outcomes.
“Poor: Evidence is insufficient to assess the effects on health outcomes because of the low number or power of studies, important flaws in their design or conduct, gaps in the chain of evidence, or lack of information on important health outcomes.”
The USPSTF assigns one of five grades (A, B, C, D, and I) to its recommendations to reflect the strength of evidence and magnitude of net benefit (benefits minus harms):
“A. The USPSTF strongly recommends that clinicians provide [the service] to eligible patients. The USPSTF found good evidence that [the service] improves important health outcomes and concludes that benefits substantially outweigh harms.
“B. The USPSTF recommends that clinicians provide [this service] to eligible patients. The USPSTF found at least fair evidence that [the service] improves important health outcomes and concludes that benefits outweigh harms.