Positive and Negative Consequences of Screening

Every medical activity has positive and negative consequences, and screening is no exception.  Potential benefits include improved prognosis for those with screen-detected cancers, the possibility of less radical treatment, reassurance for those with negative test results, and resource savings if treatment costs are reduced because of less radical treatments.  The optimal outcome is a reduction in cancer mortality.  Potential negative effects of screening include physical, economic, and psychological consequences of false-positive and false-negatives, the potential for over diagnosis, the potential carcinogenic effects of screening, and the labeling phenomenon.  The last refers to the fact that telling individuals that they have cancer may change how they see themselves or how others see them.  In addition, Baines has noted the largely unexplained increase in cancer among the unscreened group as a negative consequence of screening.
Physicians should engage patients in discussions of the risk and benefits of cancer screening.  Because most people overestimate the risks for certain type of cancers (eg. Breast), they may inflate the need for screening and the potential benefits.  For some cancers, such as colorectal cancer, people may under estimate their personal susceptibility and may need encouragement to consider screening, with positive as well as negative consequences.  In the case of prostate cancer, for which the evidence is still equivocal and population-based screening is not recommended, it is especially important that men understand the limitations of screening and make informed decisions with full understanding of the potential downstream effects of positive and negative test results.  Informed decision making increasingly is becoming a paradigm with the potential to be achieved in contemporary clinical practice.  Informed decision making occurs when an individual understands the disease or condition being addressed and also comprehends what the clinical service involves, including its benefits, risks, limitations, alternatives, and uncertainties; has considered his or her own preferences, as appropriate; believes he or she has participated in decision making at a level that he or she desires; and makes a decision consistent with his or her preferences.  Decision aids are tools used to help patients examine the nature of screening tests and their benefits and limitations.
Ausoker outlined topics that should be included when helping patients to make informed decisions about cancer screening.  These include the purpose of screening; the likelihood of positive and negative findings and the possibility of false-positive or false-negative results; the uncertainties and risks involved; any significant medical, social, or financial implications of screening; and follow-up plans.