Download USMLE Step2 CK Lecture Notes 2020 pdf Easily In Format For Free
Learning Objectives
❏ Describe appropriate screening methods as they apply to neoplasms of the colon,
breast, cervix, and lung
❏ Describe epidemiological data related to incidence and prevention of common
infectious disease, chronic illness, trauma, smoking, and travel risks
CANCER SCREENING
A 39-year-old woman comes to the clinic very concerned about her risk of developing
cancer. Her father was diagnosed with colon cancer at age 43, and her mother was
diagnosed with breast cancer at age 52. She is sexually active with multiple partners
and has not seen a physician since a car accident 15 years ago. She denies any
symptoms at this time, and her physical examination is normal. She asks what is
recommended for a woman her age.
Screening tests are done on seemingly healthy people to identify those at increased risk of disease. Even if a diagnostic test is available, however, that does not necessarily mean it should be
used to screen for a particular disease.
• Several harmful effects may potentially result from screening tests.
• Any adverse outcome that occurs (large bowel perforation secondary to a colonoscopy) is
iatrogenic.
• Screening may be expensive, unpleasant, and/or inconvenient.
• Screening may also lead to harmful treatment.
Finally, there may be a stigma associated with incorrectly labeling a patient as “sick.”
For all diseases for which screening is recommended, effective intervention must exist, and the
course of events after a positive test result must be acceptable to the patient. Most important, the
screening test must be valid, i.e., it must have been shown in trials to decrease overall mortality in
the screened population. For a screening test to be recommended for regular use, it has to be
extensively studied to ensure that all of the requirements are met.
The 4 malignancies for which regular screening is recommended are cancers of the colon,
breast, cervix, and lung.
Colon Cancer
In the patient with no significant family history of colon cancer, screening should begin at age
50. The preferred screening modality for colon cancer is colonoscopy every 10 years. Other
choices include annual fecal occult blood testing and sigmoidoscopy with barium enema every
5 years.
In the patient with a single first-degree relative diagnosed with colorectal cancer before
age 60 or multiple first-degree relatives with colon cancer at any age, colonoscopy should
begin at age 40 or 10 years before the age at which the youngest affected relative was
diagnosed, whichever age occurs earlier. In these high-risk patients, colonoscopy should
be repeated every 5 years. The U.S. Preventive Services Task Force (USPSTF) does not
recommend routine screening in patients age >75.
Breast Cancer
The tests used to screen for breast cancer are mammography and manual breast exam.
Mammography with or without clinical breast exam is recommended every 1–2 years from age
50–74. The American Cancer Society no longer recommends monthly self-breast examination
alone as a screening tool. Patients with very strong family histories of breast cancer (defined as
multiple first-degree relatives) should consider prophylactic tamoxifen, discussing risks and
benefits with a physician. Tamoxifen prevents breast cancer in high-risk individuals.
Cervical Cancer
The screening test of choice for the early detection of cervical cancer is the Papanicolaou smear
(the “Pap” test). In average risk women, Pap smear screening should be started at age 21,
regardless of onset of sexual activity. It should be performed every 3 years until age 65.
As an alternative, women age 30–65 who wish to lengthen the screening interval to every
5 years can do co-testing with Pap and HPV testing. In higher risk women, e.g., HIV, more
frequent screening or screening after age 65 may be required.
Lung Cancer
Current recommendations for lung cancer screening are as follows:
• Annual screening with low-dose CT in adults age 55–80 who have a 30-pack-year
smoking history and currently smoke or have quit within past 15 years
• Once a person has not smoked for 15 years or develops a health problem substantially
limiting life expectancy or ability/willingness to have curative lung surgery, screening
should be discontinued
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