Cancer screening

today • Wednesday 27 May 2015
40
health
Know what tests to go for
Screening for cancer: Is more always better?
Unnecessary tests may do more
harm than good, say experts
Eveline Gan
eveline@mediacorp.com.sg
SINGAPORE — Holly wood actress
Angelina Jolie’s double mastectomy
and oophorectomy (ovary removal surgery) to minimise her risks
of breast and ovary cancers raised
eyebrows and discussions on cancer
screening. So did singer-songwriter
Taylor Swift’s advocating for early
screening since her mother’s cancer
diagnosis last month.
While catching and treating cancer
in its early stages improves survival
outcomes, is Hollywood’s jumping on
the cancer-prevention bandwagon
causing more anxiety than good?
It might be so in some cases. Take
breast cancer, for example. Studies
from the United States and Scandinavia have found that at least one-fifth
of breast cancers detected via screening tests are over-diagnosed, said
Dr Crystal Ng, medical director of
Executive Health Screeners at Parkway Shenton.
A n over- diagnosis is when a
screening test detects small tumours
that might never have progressed to
cause symptoms or death in a person’s
lifetime, said Dr Ng.
“The over-screening and over-diagnosis of cancer can expose a woman to the risks of cancer treatments.
They include surgical deformity or
toxicity from radiation, hormone and
chemotherapy, as well as the late effects of radiation,” she said.
An over-diagnosis may also occur when other screening tools such
as ultrasound and tumour markers
(blood test screening) are used indiscriminately, said Associate Professor
Over-diagnosis
At least a fifth
of breast cancers
detected are overdiagnosed, meaning
the screening
tests picked up
small tumours that
might never have
progressed to
cause symptoms or
death, according
to studies from the
United States and
Scandinavia.
Angelina Jolie, with husband Brad Pitt, had her breasts and ovaries removed after tests
showed she carried a mutated gene, which increases her risk of cancer. Photo: Getty Images
Philip Iau, senior consultant at Division of Surgical Oncology (Breast Surgery) at National University Cancer
Institute, Singapore (NCIS).
According to Assoc Prof Iau, an
ultrasound should be used in breast
cancer screening only when a physical
examination or mammogram picks up
something abnormal.
Continued on page 42
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health
today • Wednesday 27 May 2015
Screening for cancer: Is more always better?
Continued From page 40
“Ultrasound should not be used as
a first-line screening tool for breast
cancer. Ultrasound is over-sensitive
and may pick out masses that can be
indistinguishable from cancer, even in
normal breasts.
“This leads to over-biopsy, anxiety
and often, insurance discrimination”,
said Assoc Prof Iau.
FALSE ALARMS
Then, there’s the issue of false-positive results. This happens when a test
shows that a disease is present, even
though it is not.
Said Dr Ng: “Such test results can
cause anxiety, and are usually followed
by additional tests and procedures that
can potentially harm the patient.”
At the National Cancer Centre
Singapore (NCCS), Associate Professor Koo Wen Hsin, senior consultant at the Division of Medical Oncology, has encountered patients who
were referred to the centre because
their blood tests showed high levels of
CA 19.9, a tumour marker for pancreatic cancer.
However, Assoc Prof Koo noted,
WHICH CANCER SCREENING TESTS
SHOULD YOU CONSIDER having?
Dr Crystal Ng, medical director of Executive Health
Screeners at Parkway Shenton, shares the tests available.
Consult your doctor for further advice.
Basic screening tests
Screening test
Screen for
Recommended for
Screening
frequency
Faecal Immunochemical
Test (FIT)
Colorectal
cancer
50 years old and
above
Yearly
Colonoscopy
Colorectal
cancer
50 years old and
above
Every decade
Additional tests for women
Pap smear
Cervical
cancer
25-69 years old,
who have
had sexual
intercourse
Every three
years
Mammogram
Breast
cancer
50 to 69 years
old
Every two
years
Source: parkway shenton
These patients
have gone
for extensive
endoscopy,
CT scans and
MRI scans.
None of them
had cancers.
All stopped
checking after
several years
but the fear
lingered.
Associate
Professor
Koo Wen Hsin
Senior consultant
at National Cancer
Centre Singapore, on
patients who were
given false-positive
test results
other non-cancer conditions, including
infection or inflammation in the gastrointestinal tract, liver, gall bladder
and pancreas, can also lead to higher
levels of CA 19.9.
Said Assoc Prof Koo: “These
patients have gone for extensive
endoscopy, CT scans and MRI scans.
None of them had cancers. All stopped
checking after several years but the
fear lingered.”
Another anxiety-inducing example is the use of tumour marker
CA 125 to screen for ovarian cancer in
women who have no symptoms. This
test is often included as part of executive-health screening packages, said
Associate Professor A Ilancheran, senior consultant at Division of
Gynaecologic Oncology at NCIS.
Routine screening for ovarian cancer in the average-risk population is
discouraged because there is currently no effective screening strategy for
it, said Associate Professor Jeffrey
Low, head and senior consultant of
the Division of Gynaecologic Oncology at NCIS.
According to Assoc Prof Ilancheran, professional gynaecologic oncology societies have specifically recommended that CA 125 not be used for
ovarian-cancer screening in women
with no symptoms.
Assoc Prof Low explained that
tumour markers like CA 125 are not
specific enough. The test can show
elevated levels even when there is no
cancer, because of conditions such as
menstruation and ovulation.
“However, the test may also indicate normal levels in half of earlystage ovarian cancer cases. Therefore,
an elevated CA 125 is usually a false
alarm but a normal CA 125 is not reassuring either,” he said.
Tumour markers are substances
that are made by cancer cells. However, they can also be produced by normal cells in the body in response to
non-cancerous conditions, although
they are produced at much higher levels when there is cancer, said Dr Ng.
“Not everyone with a particular
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health
today • Wednesday 27 May 2015
Screening tests recommended
for high-risk groups
The decision to screen is made on an individual level, based on the
person’s risk factors such as family history of hereditary or chronic
diseases, as well as exposure to factors, such as smoking, that can
lead to disease.
Screening test
Screen for
Recommended for
Screening
frequency
Every 5 years
if CT colonography is
negative.
Otherwise,
as advised by
your doctor.
Computed
Tomography
(CT) Colonography
Colorectal
cancer
Those aged
above 50, and
those not going for
colonoscopy
or FIT
AlphaFoetoProtein
(AFP) and
Ultrasound
Hepatobiliary
System
Liver
cancer/
Hepatocellular
carcinoma
(HCC)
Hepatitis B
carriers and
those with liver
cirrhosis
Annually for
each test
Nasoscopy
and tumour
marker for
NPC
Nasopharyngeal
carcinoma
(NPC)
Individuals with
a strong family
history of NPC
As advised by
your doctor
ProstateSpecific
Antigen
(PSA)
Prostate
cancer
Men aged 50
to 75 and those
with a strong
family history
of prostate
cancer
Yearly or as
advised by
your doctor
Magnetic
Resonance
Imaging
(MRI) Breast
Breast
cancer
BRCA carriers
Yearly
Transvaginal
Ultrasound
Ovarian
cancer
BRCA carriers
and women at
high risk of
BRCA mutation
As advised by
your doctor
Source: parkway shenton
type of cancer will have a higher level of tumour marker associated with
that cancer. Moreover, tumour markers have not been identified for every
type of cancer,” she said.
Even so, that does not mean these
tests do not pick up cancers, said
Assoc Prof Koo.
Dr Ng recalled a woman who had
insisted on including all available tests
for tumour markers in a health check
package for her parents, who were in
their 50s.
“She wanted peace of mind although her parents did not have any
significant family history and medical
concerns. Her father’s tumour marker
alpha fetoprotein was at an exceedingly high level. We got the family back to
do further diagnostic tests and confirmed it was liver cancer,” said Dr Ng.
Sometimes, MORE IS BETTER
For colorectal cancer, early screening is always better even when there
is no family history of the cancer, said
Dr Cheong Wai Kit, senior consultant
at the Division of Surgical Oncology
(Colorectal Surgery) at NCIS.
“Screening detects polyps that
must be removed before they turn malignant. The earlier the stage of the
colorectal cancer detected and treated, the higher the chance of survival.
However, this screening is presently underutilised in Singapore,” said
When early
screening helps
This is especially
so for colorectal
cancer, even when
there is no family
history of the
cancer, say experts.
Screening can
detect polyps which
can be removed
before they turn
malignant.
According to
oncologists, cervical
cancer is another
preventable cancer
that can be picked
up by Pap smear.
Its precancerous
stage can be easily
treated before
cancer forms.
Dr Cheong. The same goes for cervical cancer, which is the most preventable cancer and fulfils the World
Health Organization (WHO) criteria
for screening and prevention, said Assoc Prof Low.
Said Dr Ida Ismail Pratt, associate
consultant at the Division of Gynaecologic Oncology at NCIS: “Cervical
cancer is the only cancer that can be
effectively screened to stop the disease from developing all together. This
is the only cancer where the cause is
known (due to the human papillomavirus) and can be detected with a Pap
smear — a sensitive, easy-to-use test.
The precancerous stage is also easily
treated before cancer develops.”
She recommended women aged 25
to 69 years old, who have had sexual
activity, to go for regular Pap smears
every three years.
Whether a person should consider
screening beyond the recommended
basics (see tables on left) also depends
on his/her individual risk factors.
“For the general population with
no risk factors, basic screening tests
that are inexpensive and low-risk
will do. For those who have high-risk
factors like a strong family history
or existing illness linked to cancer,
more sophisticated, costly and invasive tests are recommended,” said
Assoc Prof Koo.
It is best to speak to your family
doctor, who can advise you on the
screening tests to go for based on your
risk profile, said Dr Ng.