Screening tests

Oxford American handbook of oncology. Second Edition. Oxford University Press (2015)

In screening, it is also important to have a target population at increased risk to avoid applying the test without benefit in individuals at low risk of cancer. In screening for the common cancers, where the incidence is highly age-dependent, the age range should be that in which the disease is relatively more common and yet in which the patients are likely to be fit enough for curative treatment.

Several other predictors of risk may be important, including family history, particularly now that we can detect specific genetic mutations and to use these to screen close relatives. Examples of this include mutations in the APC gene in familial adenomatous polyposis, DNA mismatch repair genes in hereditary non-polyposis colorectal cancer (Lynch syndrome), and BRCA1 and -2 in familial breast and ovarian cancer.

A screening test should be acceptable, safe, and reasonably inexpensive, so that it will be adopted by the target population. It must also be remembered that screening may cause psychological harm as well as physical harm. The benefits gained through cancer screening must outweigh such morbidity, and society must decide whether the health gain justifies any risk and the associated costs.

When a screening program is established, it is important that the diagnostic facilities are adequate. Similarly, treatment of early disease must be associated with minimal morbidity and mortality.

Randomized trials of screening programs have been done in breast and colorectal cancer, and in both instances screening has been shown to significantly reduce cancer mortality.

Although guidelines vary from one agency to another, current screening recommendations for early detection of cancer in asymptomatic individuals of average risk from the American Cancer Society include:

  • Breast cancer screening with breast self-exam and clinical breast exam in women starting at age 20 and annual mammography starting at age 40.
  • Colorectal cancer screening stating at age 50 in both men and women with annual fecal occult blood testing or a fecal immunochemical test and either flexible sigmoidoscopy or double contrast barium enema every five years or colonoscopy every 10 years.
  • Prostate cancer screening in men at age 50 with digital rectal examination and a prostate-specific antigen (PSA) annually.
  • Cervical cancer screening in women starting within three years of the start sexual activity and no later than age 21.

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