Screening - examinations & tests done on patient with no symptoms to detect early disease.
The Pros & Cons
Potential Benefit: Screening may reduce cancer morbidity since treatment for earlier-stage cancers is often less aggressive.
Potential harms:
- Small risks of serious complications resulting from screening tests. This may be immediate (e.g., perforation with colonoscopy) or delayed (e.g., potential carcinogenesis from radiation).
- Another harm is the false-positive test result, which will lead to anxiety and unnecessary invasive diagnostic procedures.
- Also, a false-negative screening test may falsely reassure an individual with subsequent clinical signs or symptoms of cancer and thereby actually delay diagnosis.
Key Elements of Screening
- Screening is a means of detecting disease early in asymptomatic people.
- Positive results of examinations, tests, or procedures used in screening are usually not diagnostic but identify persons at increased risk for the presence of cancer. Further evaluation is needed following a positive screening result.
- Diagnosis is corfirmation of disease by biopsy or tissue examination in the work-up.
Note: Procedure & Tests done (i.e. investigations) on symptomatic patients is not screening
Detection methods
- Visual observation (direct or assisted) is the most widely available examination for the detection of cancer. It is useful in identifying suspicious lesions in the skin, retina, lip, mouth, larynx, external genitalia, and cervix.
- Palpation is the second most available detection procedure to detect lumps, nodules, or tumors in the breast, mouth, salivary glands, thyroid, subcutaneous tissues, anus, rectum, prostate, testes, ovaries, and uterus and enlarged lymph nodes in the neck, axilla, or groin.
- Examinations and tests for internal cancer (e.g., endoscopy, colonoscopy, x-rays, magnetic resonance imaging, or ultrasound). Laboratory tests, such as the pap smear or the faecal occult blood test are used for detection of specific cancers.
When to start, What tests , How often?
The type, periodicity, and commencement of screening will depend on whether the asymptomatic patient has a normal risk or higher risk of having cancer. Example: Patients with family history of Cancer colon, need to be tested at an earlier age and more often.
Screening Guidelines for some common cancers ( Adapted from American Cancer Society)
1. Breast Cancer
- Yearly mammograms starting at age 40 and continuing for as long as a woman is in good health.
- Clinical breast exams (CBE) should be part of a periodic health exam, about every three years for women in their 20s and 30s and every year for women 40 and over.
- Women should report any breast change promptly to their health care providers. Breast self-exam (BSE) is an option for women starting in their 20s.
- Women at increased risk (e.g., family history, genetic tendency ) should talk with their doctors about the benefits and limitations of starting mammography screening earlier, having additional tests (e.g., breast ultrasound or MRI), or having more frequent exams.
2. Colon and Rectal Cancer
Beginning at age 50, both men and women at average risk for developing colorectal cancer should follow one of these five testing schedules:
- yearly faecal occult blood test (FOBT)* or fecal immunochemical test (FIT)
- flexible sigmoidoscopy every 5 years
- yearly FOBT* or FIT plus flexible sigmoidoscopy every 5 years**
- double-contrast barium enema every 5 years
- colonoscopy every 10 years
*For FOBT, the take-home multiple sample method should be used.
**The combination of yearly FOBT or FIT plus flexible sigmoidoscopy every 5 years is preferred over either of these options alone.
All positive tests should be followed up with colonoscopy.
People should begin colorectal cancer screening earlier and/or undergo screening more often if they have any of the following colorectal cancer risk factors.
- a personal history adenomatous polyps, chronic inflammatory bowel disease
- a strong family history of colorectal cancer or polyps (cancer or polyps in a first-degree relative younger than 60 or in two first-degree relatives of any age)
Note: a first degree relative is defined as a parent, sibling, or child.
3. Cervical Cancer
- All women should begin cervical cancer screening about 3 years after they begin having vaginal intercourse. Screening should be done every year with the regular Pap test or every 2 years using the newer liquid-based Pap test.
- Beginning at age 30, women who have had 3 normal Pap test results in a row may get screened every 2 to 3 years with either the conventional (regular) or liquid-based Pap test. Women who have certain risk factors such as diethylstilbestrol (DES) exposure before birth, HIV infection,or a weakened immune system due to organ transplant, chemotherapy, or chronic steroid use should continue to be screened annually.
- Another reasonable option for women over 30 is to get screened every 3 years (but not more frequently) with either the conventional or liquid-based Pap test, plus the HPV DNA test (new)
- Women 70 years of age or older who have had 3 or more normal Pap tests in a row and no abnormal Pap test results in the last 10 years may choose to stop having cervical cancer screening. Women with DES exposure before birth, HIV infection or a weakened immune system should continue to have screening as long as they are in good health.
- Women who have had a total hysterectomy (removal of the uterus and cervix) may also choose to stop having cervical cancer screening, unless the surgery was done as a treatment for cervical cancer or precancer. Women who have had a hysterectomy without removal of the cervix should continue to follow the guidelines above.
4. Endometrial (Uterine) Cancer
The American Cancer Society recommends that all women should be informed about the risks and symptoms of endometrial cancer, and strongly encouraged to report any unexpected bleeding or spotting to their doctors.
5. Prostate Cancer
- Beginning at age 50, men who have at least a 10-year life expectancy - the prostate-specific antigen (PSA) blood test and digital rectal examination (DRE) should be offered annually.
- Men at high risk (a strong family of one or more first-degree relatives (father, brothers) diagnosed at an early age) should begin testing at age 45.
- Men at even higher risk, due to multiple first-degree relatives affected at an early age, could begin testing at age 40. Depending on the results of this initial test, no further testing might be needed until age 45.
