The PDQ Screening and Prevention Editorial Board summarizes its understanding of the level of the evidence for the magnitude of the effect (including absolute and relative risks) for both the benefits and the harms of implementing cancer screening and prevention interventions. The Editorial Board uses the term "Level of Evidence" to refer to the certainty of its estimate of the health effects of implementing the intervention in question.
Varying levels of evidence support each PDQ screening or prevention summary. Evidence that indicates, within a narrow range, the direction and magnitude of the effect on health outcomes is termed "solid" evidence. Evidence that allows an estimate of the direction and magnitude of the health outcomes within a broader range, but still allows a reasonably certain estimate, is termed "fair." Evidence that allows either no estimate at all or only an estimate that is very broad is termed "inadequate".
Coenzyme Q10 (commonly known as CoQ10) is a compound that is made naturally in the body. The body uses it for cell growth and to protect cells from damage that could lead to cancer (see Question 1).
Animal studies have shown that CoQ10 helps the immune system work better and makes the body better able to resist certain infections and types of cancer (see Question 5).
Clinical trials have shown that CoQ10 helps protect the heart from the damaging side effects of doxorubicin, a drug...
The highest Level of Evidence ("solid") is that obtained from several well-designed and well-conducted randomized controlled trials (RCTs) in generalizable settings with generalizable populations that report evidence about both benefits and harms. It is, however, not always practical to conduct such trials to address every question within the field of screening and prevention. Thus, the PDQ Editorial Board does consider "fair" evidence in estimating the benefits and harms of an intervention in the general population. When the evidence for the benefits and/or harms of an intervention is "inadequate," the Board states this finding.
The PDQ Editorial Board evaluates evidence in 2 steps. The first step is to describe the evidence within 5 domains (see below); the second is to judge the overall "level" of evidence as "solid," "fair," or "inadequate." The Board conducts the same process separately for potential benefits and potential harms of each intervention. The PDQ Editorial Board does not explicitly assess the "net benefit" (i.e., benefits minus harms) of interventions, nor does it make recommendations.
The question at issue for the Board is to determine the direction and magnitude of important health effects from introducing the intervention into the general population. This is a question of effectiveness rather than of efficacy only, and the Board seeks evidence about effectiveness as well as efficacy. When only efficacy evidence is available, the Board must judge the additional uncertainty involved with estimating the actual health impact of widespread implementation.
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WebMD Public Information from the National Cancer Institute
May 28, 2015
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