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Cancer screening
Dr V.Mehrzad
Hematologist&Oncologist
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Cancer screening is synonymous with secondary
prevention, in which earlier therapeutic intervention
is possible through screening an asymptomatic
population to identify cancer at an earlier stage
than it would have been diagnosed in the absence
of screening
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The expectation is that early diagnosis and
treatment lead to a reduction in mortality from the
disease and/or a reduction in the severity of the
disease
Principles of Screening
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1-The disease should be an important public health
problem in terms of its frequency and/or severity
2-The natural history of the disease presents a
window of opportunity for early detection
3-An effective treatment should be available that
favorably alters the natural history of the disease
4-A suitable screening test should be available, that
is, one that is accurate, acceptable to the
population, fairly easy to administer, safe, and
relatively inexpensive
Methods of Screening for Colorectal
Cancer
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Colorectal cancer screening is unique in that there
are at least five screening methods that are
recommended in existing guidelines
Fecal Occult Blood Testing
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Although it remains the only method to have been
proven effective in replicated randomized trials
against usual care, after years of increasing, the
rates of screening by FOBT have been declining in
general
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These immunochemical tests have been studied in
case-control studies, particularly in Japan, and by
comparing them to the older guaiac-based tests in
general have shown themselves to have lower rates
of false positivity and equal or greater sensitivity
for polyps
Stool DNA Testing
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such methods will need to be evaluated in large
populations to determine efficacy relative to
already accepted methods of screening
Endoscopy
Rigid Proctoscopy/Sigmoidoscopy
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It is estimated that flexible sigmoidoscopy will find
60% to 83% of cancers and polyps found by
colonoscopy
Colonoscopy, which allows a complete examination
of the rectum and colon to the cecum, has become
the screening method for colorectal cancer
preferred by gastroenterologists and many other
physicians and public health experts
NCCN consensus guidelines
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The National Comprehensive Cancer Network (NCCN), a
multispecialty panel, issued revised screening guidelines for
CRC in January 2010
These guidelines recommend colonoscopy every ten years,
when available, as the preferred screening strategy
Suggested alternatives are annual stool testing with guaiac
or immunochemical reagent; or sigmoidoscopy every five
years with or without annual stool testing
The NCCN advises barium enema only when colonoscopy
cannot be performed and did not come to consensus
regarding CT colonography or fecal DNA as screening
modalities
Screening for breast cancer
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Major risk factors for breast cancer in women are
age, genetic predisposition and estrogen exposure
IMAGING STUDIES
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Mammography remains the mainstay of screening for
breast cancer
Ultrasonography is commonly used for diagnostic
follow-up of an abnormality seen on screening
mammography, to clarify features of a potential lesion
The role of magnetic resonance imaging (MRI) for
breast cancer screening is emerging; currently MRI
screening, in combination with mammography is
targeted to high risk patients
Newer tests, such as tomography, are under evaluation
Full-field digital mammography
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Full-field digital mammography is similar to
traditional film-screen mammography except that
the image is captured by an electronic detector and
stored on a computer
film mammography remains an acceptable
screening modality for all women
Digital mammography, when available, may offer a
small screening advantage in women younger than
50 years old
Frequency of mammography
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An observational study comparing mammogram
screening annually or every two years for
predominantly Caucasian women aged 50 to 69
years in Vermont, US (annual) and Norway
(biennial) found no significant difference in breast
cancer detection rate or prognostic stage
Screening with mammography
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The American Cancer Society , American College of
Radiology , American Medical Association , the
National Cancer Institute , the American College of
Obstetrics and Gynecology and the National
Comprehensive Cancer Network
(NCCN) recommend starting routine screening at
age 40
The American Academy of Family Physicians
recommends screening mammography every one to
two years for women ages 40 and older
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The USPSTF recommends biennial mammography
screening for women who are screened
Most other North American groups recommending
screening for women in their 40s have tended to
shift towards annual examinations because of the
evidence of more rapid tumor growth in younger
women
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The American Cancer Society recommends clinical breast
examination every three years from age 20 to 39, and
annually thereafter
The US Preventive Services Task Force concludes that
evidence is insufficient to assess additional benefits of
clinical breast examination beyond mammography, and the
Canadian Task Force on Preventive Health Care
recommends clinical breast examination with mammography
every one to two years beginning at age 40 and 50,
respectively
The World Health Organization does not recommend
clinical breast examination
No group recommends clinical breast examination alone
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Guidelines from the National Comprehensive Cancer Network (NCCN)
recommend annual breast MRI in addition to mammography for women with
a strong family history or genetic predisposition The criteria specified
include:
BRCA 1 or 2 mutation carriers
Untested women who have a first degree relative with a BRCA 1 or 2
mutation
Lifetime risk of breast cancer of 20 to 25 percent or more, defined by
models that are largely dependent on family history (eg, BRCAPRO and
others)
Received radiation treatment to the chest between ages 10 and 30
Genetic mutation in the TP53 or PTEN genes
Cervical cancer
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Cervical cancer screening guidelines in the US are
issued by three major organizations: the US
Preventive Services Task Force (USPSTF) , the
American Cancer Society (ACS) , and the American
College of Obstetricians and Gynecologists
(ACOG)
Starting age
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All three organizations strongly recommend
screening for cervical cancer
2009 ACOG guidelines recommend initiating
screening at age 21; older guidelines from the
USPSTF and ACS recommend initiating screening at
age 21 or three years after the onset of sexual
activity, whichever comes first
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The USPSTF recommends stopping screening at age
65, and the ACS suggests stopping at age 70 for
women who have had adequate recent screening
with normal Pap smears and are not otherwise at
high-risk; ACOG states it is reasonable to
discontinue screening in women at 65 to 70 years of
age who have had three or more consecutive
normal smears, and no abnormal results in the
previous ten years
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The USPSTF recommends screening at least every
three years; ACS advocates annual screening
(biennial if using liquid-based testing) and ACOG
biennial for women under age 30 and reducing the
frequency to every two to three years for women
aged 30 and older who have had three consecutive
normal Pap tests, or no more than every three years
if they also are tested for HPV DNA
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Both ACS and ACOG allow for screening using liquid
based cytology or a combination of cytology plus HPV
testing (the latter for women 30 and older)
When screening is performed with combination of
cytology and HPV test, both ACS and ACOG
recommend that the screening interval be no more often
than every three years
The USPSTF makes no recommendation for or against
liquid-based technology or HPV testing, due to
insufficient evidence
prostate cancer
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The American Cancer Society (ACS) emphasizes the
need for involving men in the decision whether to screen
for prostate cancer
Men need to have sufficient information regarding the
risks and benefits of screening and treatment to make
an informed and shared decision; providing them with a
decision aid may facilitate the decision-making process
For men who decide to be screened, the ACS
recommends PSA testing with or without DRE for
average-risk men beginning at 50 years of age
Screening should not be offered to men with a life
expectancy less than 10 years
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Men whose initial PSA level is greater than or
equal to 2.5 ng/mL should undergo annual testing;
men with a lower initial level can be tested every
two years
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The guidelines also recommend beginning screening
discussions at age 40 to 45 in patients at high-risk
of developing prostate cancer (eg, black men and
men with a first-degree relative with prostate
cancer diagnosed before age 65)
The guideline also recommends keeping the biopsy
referral threshold at 4.0 ng/mL
Screening for ovarian cancer
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Clinical studies of ultrasonography and the CA 125
radioimmunoassay have so far been too small to
provide sufficient support to justify a policy of
routine ovarian cancer screening for most women
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No definitive large randomized controlled trials
have been completed to show whether any
screening strategy decreases mortality from ovarian
cancer
Nevertheless, a practical clinical approach to the
issue of screening can be based upon assessment of
an individual woman's risk of ovarian cancer
Women at average risk
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Screening for ovarian cancer with CA 125 or
ultrasound is not currently recommended for
premenopausal and postmenopausal women without
a family history of ovarian cancer
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The predictive value of either test alone (less than
3 percent) yields an unacceptably high rate of
false-positive results and attendant morbidity and
costs
Women at higher risk
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Postmenopausal women with this type of limited family
history may be reasonable candidates for screening
because of an elevated risk of developing ovarian
cancer
For women who desire screening, a strategy of annual
CA 125 testing with transvaginal ultrasound in women
with CA 125 levels above 30 U/mL is the approach
that is best supported by existing data
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Women with a suspected hereditary ovarian cancer
syndrome should be referred to a genetic counselor
for consideration of testing for BRCA1 and BRCA2
mutations
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Women who are found to have BRCA1 and/or
BRCA2 mutations should be referred to a
gynecologic oncologist for follow-up
Protocols in clinical use for surveillance of such
women include combinations of pelvic examinations,
CA 125 and other tumor marker measurements,
vaginal ultrasonography, and color Doppler
imaging
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The optimal interval for screening has not been
determined
Expert groups have recommended a six-month
interval , and this is a reasonable option
However, the evidence indicate limited
effectiveness of screening in this population, and
physicians and patients should not be falsely
reassured by negative screening test results
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Prophylactic oophorectomy at the completion of
childbearing or by age 35 has generally been
recommended for women with hereditary ovarian
cancer syndromes
Evidence from prospective and retrospective studies
of women with BRCA1 or BRCA2 mutations
demonstrated a substantial reduction in subsequent
ovarian and breast cancers in women who had
prophylactic oophorectomy compared with those
undergoing surveillance only
Screening for lung cancer
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Systematic screening with either CT or chest x-ray is
not unequivocally recommended by any major
professional organization
The US Preventive Services Task Force (USPSTF)
concluded that current evidence was insufficient to
recommend for, or against, screening for lung
cancer
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Lung cancer is the leading cause of cancer-related
death
Prevention (promoting smoking cessation) is likely to
have far greater impact on lung cancer mortality
than is screening
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Early trials of chest x-ray screening in males at high
risk for lung cancer found no mortality benefit for xray alone or x-ray plus sputum cytology
Screening CT scans in high risk groups identify a
high prevalence of stage 1 lung cancer and greater
than 50 percent prevalence of benign nodules
There are no data yet available from randomized
studies of CT scanning
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While awaiting results from ongoing randomized
control trials, we suggest not screening
asymptomatic individuals for lung cancer outside of
a clinical trial
Plain chest X-ray has been shown to be ineffective
for lung cancer screening
For individuals committed to screening for lung
cancer, we suggest screening with chest CT
Screening and early detection of
melanoma
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The clinician examination for skin cancer and
ascertainment of risk factors can be carried out in
tandem, taking only a few minutes, with a source of
bright light and a magnifying lens
Melanomas can occur anywhere on the skin surface,
but are frequently located on the back and other
areas that may be easy to miss with self-inspection
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The A, B, C, D, Es of melanoma recognition are valuable
for patient education and for all clinicians :
Asymmetry
Border irregularities
Color variegation (ie, different colors within the same
region)
Diameter greater than 6 mm
Enlargement or evolution of color change, shape, or
symptoms
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A seven point checklist was designed in England and is a sensitive
screening test for the early detection of melanoma. The checklist
includes three major features :
Change in size
Change in color
Change in shape
There are also four minor features :
Inflammation
Bleeding or crusting
Sensory change
Lesion diameter greater than 6 mm
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The American Cancer Society recommends that all
adults receive at least a baseline total body skin
cancer screening examination from a clinician, with
subsequent skin examinations at the clinician's
discretion as determined by risk status