What is
a cancer diagnosis?
Diagnosis is not the same as
detection. Cancer may be detected
when symptoms or abnormalities, such
as a lump or growth, are recognized
by a patient or doctor. After a
cancer is detected, it still must be
carefully diagnosed. A diagnosis
is an identification of a particular
type of cancer. When making a
diagnosis, the initial signs and
symptoms are investigated through a
variety of tests in order to
identify whether cancer is causing
them and, if so, what type of cancer
it is. For example, breast cancer
may be detected when a patient
notices a lump, but it must be
carefully evaluated with a number of
tests in order to determine an
accurate diagnosis. The diagnosis
describes what type of breast cancer
it is (i.e. 'ductal' if it started
in the ducts of the breast or
'lobular' if it started in the
lobes) and how advanced it is.
What is a cancer stage?
Following a diagnosis of cancer,
the most important step is to
accurately determine the stage of
cancer. Stage describes how far the
cancer has spread. (Some cancers,
such as leukemia, may not be
staged.) Each stage of cancer may be
treated differently. In order for
you to begin evaluating and
discussing treatment options with
your healthcare team, you need to
know the correct stage of your
cancer. There are many staging
systems, but TNM is the most common.
'T' refers to the size of the tumor,
'N' to the number of lymph nodes
involved, and 'M' to metastasis. TNM
staging measures the extent of the
disease by evaluating these three
aspects and assigning a stage, which
is usually between 0-4. Generally,
the lower the stage, the better the
treatment prognosis (outcome).
- Stage 0 - precancer -
Stage 1 - small cancer found only in
the organ where it started
- Stage 2 - larger cancer that may
or may not have spread to the lymph
nodes - Stage 3 - larger
cancer that is also in the lymph
nodes - Stage 4 - cancer
in a different organ from where it
started
How is
prognosis determined?
The probable course and/or outcome
of the cancer is called the
prognosis. Identifying factors that
indicate a better or worse prognosis
may help you and your doctor plan
your treatment. There are many
factors that help determine your
prognosis. Some of these include:
- Your age - Your level of
physical fitness - Size of
your cancer - Stage of
your cancer -
Aggressiveness of your cancer
(cancer cells that are growing and
dividing rapidly are considered more
aggressive)
Your doctor will
evaluate all possible factors to
determine your prognosis.
Recently, the genetic make-up of
cancer is being increasingly
recognized as an important
prognostic factor. For example, some
genes have been associated with an
aggressive course or tendency to
recur. Identification of these in an
early stage cancer may indicate a
poor prognosis. Some research
suggests that the genetic make-up of
the cancer may be even more
important for determining prognosis
than the stage of the cancer.
How
is cancer diagnosed?
Diagnosing cancer involves the use
of a variety of tests that provide
details about abnormal cells, which
may have been detected through
routine medical examinations,
self-examination, or reported
symptoms. More information about
these cells must be gathered in
order to identify them as malignant
(cancerous) or non-malignant
(non-cancerous), and if they are
malignant, to determine how serious
(aggressive) the particular cancer
cells are. Aggressive cancers grow
and spread more quickly than
less-aggressive or 'indolent'
cancers. There are many types of
tests specifically designed to
evaluate cancer:
- A
pathology report is based on
observation of abnormal cells under
a microscope. - Diagnostic
imaging involves visualization of
abnormal masses using high tech
machines that create images, such as
x-rays,
computed tomography (CT), positron
emission test (PET), magnetic
resonance imaging (MRI), and
combined PET/CT. - Blood
tests measure substances in the
blood that may indicate how advanced
the cancer is or other problems
related to the cancer. -
Tumor marker tests detect substances
in blood, urine, or other tissues
that occur in higher than normal
levels with certain cancers.
- Special laboratory evaluation of
DNA involves the identification of
the genetic make-up-the DNA-of the
abnormal cells.
How
does diagnosis determine treatment?
Historically, a combination of
pathological assessment (laboratory
evaluation using a microscope) and
diagnostic imaging has been used to
identify the type of cancer and its
stage, and then the treatment. Stage
indicates how extensive the cancer
is and how much it has spread.
Staging usually involves determining
the size of the primary tumor and
evaluating whether it has remained
in the tissue in which it started,
whether it has invaded other nearby
organs or tissues, and whether
cancer cells have spread to distant
locations in the body. The cancer is
then assigned a stage on a
predetermined scale of numbers and
letters, for example stage I, II,
IIIa, IIIb, IV, etc. The higher
number and letter combination
indicates more extensive spread, and
therefore a more serious condition.
Treatment is often selected based on
the stage of disease. Higher stage
cancers typically receive very
aggressive treatments and lower
stage disease less aggressive
treatment.
However, research
has indicated that identifying the
stage of disease may not be the most
accurate technique for determining
how aggressive it is. For example,
some early stage diseases may recur
or progress even after treatment,
while some late stage cancers may
stay in remission. These findings
suggest that there may be factors
other than how the cancer looks
under a microscope and how far it
has spread at the time of diagnosis
that may better indicate the
likelihood that a given cancer will
recur and/or progress. Human
genomics, which is the study of the
entire genetic material of humans,
has provided invaluable tools for
identifying the genetic components
of cancers. The mapping of the human
genome, which consists of 30,000 to
70,000 genes, has laid the ground
work for understanding the role
those genes play in human health and
disease. Cancer is many different
diseases; however, one aspect of all
cancers that is similar is damage to
the DNA resulting in uncontrolled
cell growth. Identifying the genes
for each cancer type that are
involved in the capacity grow and
spread may provide valuable
prognostic information.
As
improvements are made in the special
laboratory techniques used to
identify the genetic make-up of
cancers, this genetic information
may become a better predictor of
cancer aggressiveness and outcome
than stage, which has been the
diagnostic indicator of choice in
the past. Additionally, this genetic
information will likely play an
increasing role in directing
treatment. Specifically, the genes
involved in each cancer may indicate
more aggressive treatment for some
cancers and less aggressive
treatment for others.
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