Early detection of many cancers offers the potential
to reduce cancer morbidity and mortality. Cancer screening is a means
to detect disease at an early stage of development and subsequently
to improve outcomes. This section will provide an overview of cancer
screening practices, techniques used in the diagnosis of cancer, and
1 method of classifying the extent of most cancer at the time of diagnosis.
Screening
Cancer screening should be considered for individuals
known to be at high risk for the development of disease.367 Individuals
with rheumatoid arthritis, inflammatory bowel disease, and psoriasis
are at an increased risk of developing certain cancers and should
consider cancer screening appropriate to their underlying disease.
Periodic screening on asymptomatic individuals can identify cancer
in its earliest stages. Early detection, diagnosis, followed by early
treatment intervention are the best ways to improve clinical outcomes.367
Factors that should be considered in the screening
process include but are not limited to age, medical and familial history
of the patient, the accuracy of the test, the risks associated with
the test, necessary follow-up care, convenience, and the cost to the
patient.8021 Many
cancers are detected through direct or assisted visual observation
or palpation during a physical examination. 8035 Other
cancers require procedures, such as x-rays, magnetic resonance imaging,
ultrasound, pap smears, or blood tests, for detection.8035
Breast self-exam, mammography, and clinical breast
exam are useful tools in the early detection of breast cancer.382 According to the American Cancer Society, all females 40
years of age or older should have an annual mammogram and clinical
breast examination.359 The
American Cancer Society also recommends screening for males and females
who are at average risk for colorectal cancer starting at age 50.
These recommendations include annual fecal occult blood test or fecal
immunochemical test with sigmoidoscopy repeated every 5 years. Alternative
approaches include colonoscopy repeated every 10 years if normal and
double-contrast barium enema every 5 years if normal. 359 While the American Cancer Society does not currently recommend
routine testing for prostate cancer, it does recommend that health
care professionals discuss the potential benefits and limitations
of prostate cancer early detection testing with men before any testing
begins. This discussion should include an offer for testing with the
prostate-specific antigen blood test and digital rectal exam yearly,
beginning at age 50, to males who are at average risk of prostate
cancer and have at least a 10-year life expectancy. Earlier discussions
are recommended for males at high risk of developing prostate cancer,
including African American males and males who have a first-degree
relative (father, brother, or son) diagnosed with prostate cancer
at an early age (younger than age 65) or those with several first-degree
relatives who had prostate cancer at an early age.11814
The US Preventive Services Task Force, American
Cancer Society, the Screening and Prevention Editorial Board, and
other professional societies have developed guidelines for cancer
screening. The National Cancer Institute also publishes peer-reviewed
cancer screening information references (e.g., Physician Data Query
or PDQ®).8010,8036,8037
Diagnosis
Screening is not diagnostic. On the basis of
positive screening results, additional tests are generally required
to determine the presence of cancer. Blood and urine tests, in addition
to imaging procedures, may be used to evaluate patients.373 For
most patients with positive findings, a biopsy will be performed to
make an accurate cancer diagnosis. During a biopsy, a small piece
of tissue is removed from the suspicious mass or area of abnormality.
If the area is small enough, the entire mass is typically removed
during the biopsy. After removal, the tissue is processed and evaluated
by a pathologist.373 Tissue
expression of specific molecular markers can provide additional information
about the prognosis and decisions regarding appropriate treatment
regimens.374
Staging
Staging is the process of describing the extent
and location (i.e., above and below the diaphragm) of cancer at the
time of diagnosis.8008 The clinical stage of cancer is defined
by the primary tumor’s size, location, and extent of metastasis
of the primary tumor. Most importantly, staging helps to determine
the prognosis and, potentially, the type(s) of therapy that would
be most effective in fighting any particular cancer.359 Physical exams, lab reports, surgery reports, pathology reports,
and imaging tests all contribute to determining the stage of disease.375
The Tumor-Node-Metastasis (TNM) method, which
is accepted by the International Union Against Cancer and the American
Joint Committee on Cancer, is the most common method of staging cancer.375 It
categorizes cancer based on the size of the primary tumor (T), the
degree of lymph node involvement (N), and the presence of metastases
(M). The criteria used to define each T, N, and M descriptor varies
according with each type of cancer. The TNM combinations are then
used to define the stage of cancer: Stage 0 (in situ) through Stage IV (distant organ
metastasis).375 For intermediate stages, Stages I, II,
and III, the higher number indicates more extensive disease, greater
tumor size, or lymph node or surrounding organ involvement. Disease
stage is determined at diagnosis and does not change throughout the
life cycle of the cancer.374,375Within each TNM category, as the tumor burden throughout the
body increases, the prognosis of the patient worsens.374
Content on this page was last reviewed
on
January 31, 2010.
Content on this page was last changed on
January 12, 2010.
Rubin EH, Hait
WN. Principles of cancer treatment. In: Dale DC, Federman DD, eds.
ACP Medicine Online.
Based on: Dale DC, Federman DD, eds.
ACP Medicine.
New York, NY: WebMD, Inc.; 2003.
http://www.acpmedicine.com.
Accessed June 29, 2007.
Davidson
NE. Breast cancer. In: Dale DC, Federman DD, eds.
ACP Medicine
Online.
Based on: Dale DC, Federman DD, eds.
ACP
Medicine.
New York, NY: WebMD Professional Publishing; 2004.
http://www.acpmedicine.com.
Accessed June 29, 2007.
National Cancer Institute. PDQ cancer information summaries:
screening/detections (testing for cancer). National Cancer Institute
website.
http://www.cancer.gov/cancertopics/pdq/screening
. Updated
2008. Accessed April 3, 2008.
United States Department of Health and Human Services.
Guide to clinical preventive services. Agency for Healthcare Research
and Quality website.
http://www.ahrq.gov/clinic/cps3dix.htm#cancer
. Accessed April 14, 2008.
Rubin EH, Hait
WN. Principles of cancer treatment. In: Dale DC, Federman DD, eds.
ACP Medicine Online.
Based on: Dale DC, Federman DD, eds.
ACP Medicine.
New York, NY: WebMD, Inc.; 2003.
http://www.acpmedicine.com.
Accessed June 29, 2007.
Davidson
NE. Breast cancer. In: Dale DC, Federman DD, eds.
ACP Medicine
Online.
Based on: Dale DC, Federman DD, eds.
ACP
Medicine.
New York, NY: WebMD Professional Publishing; 2004.
http://www.acpmedicine.com.
Accessed June 29, 2007.
National Cancer Institute. PDQ cancer information summaries:
screening/detections (testing for cancer). National Cancer Institute
website.
http://www.cancer.gov/cancertopics/pdq/screening
. Updated
2008. Accessed April 3, 2008.
United States Department of Health and Human Services.
Guide to clinical preventive services. Agency for Healthcare Research
and Quality website.
http://www.ahrq.gov/clinic/cps3dix.htm#cancer
. Accessed April 14, 2008.