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• Overview of Cancer
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Cancer can sometimes be detected in asymptomatic patients via regular physical examinations and screening tests.

Physical examinations for cancers of the thyroid, oral cavity, skin, lymph nodes, testes, prostate, and ovaries should also be done during routine medical care.

Screening tests are done in asymptomatic patients at risk. The rationale is that early diagnosis may decrease cancer mortality by detecting cancer at an early and curable stage. Early detection may allow for less radical therapy and reduce costs. Risks, however, include false-positive results, which necessitate confirmatory tests (eg, biopsy, endoscopy) that can lead to anxiety, significant morbidity, and significant costs; and false-negative results, which may give a mistaken sense of security, causing patients to ignore subsequent symptoms.

Screening for cancer should be done in the following circumstances:

• When distinct high-risk groups can be identified (eg, people with certain infections, exposures, or behaviors)
• When the disorder has an asymptomatic period during which treatment would alter outcome
• When the morbidity of the disorder is significant
• When an intervention is available that is acceptable and effective at changing the natural history of the disorder

The screening tests themselves should satisfy the following criteria:

• Cost and convenience are reasonable.
• Results are reliable and reproducible.
• Sensitivity and specificity are adequate.
• The positive predictive value (probability that a person with a positive test result has or will develop a disorder or condition—see Clinical Decision Making: Testing) is high in the population screened, and few false-negative results occur.
• The test or procedure is acceptable to patients.

Recommended screening schedules are constantly evolving based on ongoing studies (see Table 4: Overview of Cancer: Screening Procedures in Average-Risk Asymptomatic People As Recommended by the American Cancer Society*).

Table 4
Screening Procedures in Average-Risk Asymptomatic People As Recommended by the American Cancer Society* Type of Cancer Procedure Frequency Breast cancer Breast self-examination (BSE) Monthly or periodically after age 20 Clinical breast examination Every 3 yr between ages 20 and 39, then yearly Mammography Yearly, starting at age 40 MRI Yearly (in addition to mammography), starting at age 40 for women at high risk or with dense breasts seen on mammogram and as directed by their health care practitioner Cervical cancer Papanicolaou (Pap) test sometimes with the human papillomavirus test Yearly (or every 2 yr if the newer liquid-based test is used) in all women within 3 yr of first vaginal intercourse but no later than age 21† After age 30, every 3 yr if ≥ 3 consecutive examinations are normal and risk is not high Cervical, uterine, and ovarian cancers Pelvic examination Every 1 to 3 yr between ages 18 and 40, then yearly Prostate cancer Blood test for prostate-specific antigen Yearly after age 50 (or age 45 for men at high risk)‡ Rectal and colon cancer Fecal occult blood or Yearly, starting at age 50 Flexible sigmoidoscopy or Every 5 yr, starting at age 50 Colonoscopy Every 10 yr, starting at age 50 *Examinations for cancers of the thyroid, oral cavity, skin, lymph nodes, testes, and ovaries should also be done during routine medical care. †Most women > 70 yr need Pap tests less often or can stop electively. ‡Patient and physician should determine the schedule for prostate cancer screening. Modified from the American Cancer Society Guidelines for the Early Detection of Cancer

Last full review/revision August 2008 by Bruce A. Chabner, MD; Elizabeth Chabner Thompson, MD, MPH

Content last modified August 2008