Working Procedures

B. SCIENTIFIC REVIEW AND EVALUATION

7. Evaluation

Evaluations of the screening procedures
An evaluation of the degree of evidence of the efficacy and of the effectiveness of each screening procedure is formulated according to the following definitions.

Sufficient evidence for the efficacy and effectiveness of a cancer-preventive activity will apply when screening interventions by a defined procedure are consistently associated with a reduction in mortality from the cancer and/or a reduction in the incidence of invasive cancer, and chance and bias can be ruled out with reasonable confidence.

Limited evidence for the efficacy and effectiveness of a cancer-preventive activity will apply when screening interventions by a defined procedure are associated with a reduction in mortality from the cancer and/or a reduction in the incidence of invasive cancer or a reduction in the incidence of clinically advanced cancer, but bias or confounding cannot be ruled out with reasonable confidence as alternative explanations for these associations.

Inadequate evidence for the efficacy and effectiveness of a cancer-preventive activity will apply when data are lacking, or when the available information is insufficient or too heterogeneous to allow an evaluation.

Sufficient evidence that the screening procedure is not efficacious in cancer prevention will apply when any of the following cases hold:

  • The procedure does not result in earlier diagnosis than with standard methods already in use;
  • The survival of cases detected at screening is no better than that of cases diagnosed routinely;
  • The screening interventions are consistently associated with no reduction in mortality from or incidence of invasive cancer, and bias can be ruled out with reasonable confidence.

In the case of limited or inadequate evidence, the Working Group should highlight those aspects of the procedure for which information is lacking, and which led to the uncertainty in evaluation. This will provide indications of research priorities.

Overall evaluation
The body of evidence for each screening procedure is considered as a whole, and summary statements are made about the cancer-preventive effects of the screening intervention and other beneficial or adverse effects, as appropriate. The overall evaluation is usually in the form of a narrative. The data on the effectiveness of the screening intervention are summarized, including the factors that determine its success and failure under routine conditions. Finally, the balance between expected benefit and harm is described.

 

Posted 27 May 2014