Diagnostic
Tests For Liver CancerAfter the initial examination by the doctor, the
doctor likely will want to order a number of liver blood tests as well as some
imaging studies. This is necessary to confirm the suspicion of liver
cancer and to rule other diseases in or out. Here is a list of blood tests that
often are ordered by physicians who just examined a patient with a possible liver
cancer. The purpose of the tests is to establish the present liver function and
whether or not the constellation of the test results supports the diagnosis of
liver cancer. Other causes of liver disease are also ruled out such as
pernicious anemia, which is due to vitamin B-12 deficiency. The traditional liver
function tests (transaminases etc.) help to distinguish whether there is an obstruction
of a biliary duct within the liver, whether there is cirrhosis of the liver, hepatitis
or normal liver function.
| Blood tests for liver
cancer work-up | | Blood
test type: | Explanation
why test is done: | | CEA
(=carcinoembryonic antigen) | tumor marker
| | AFP (=alpha-fetoprotein) | tumor
marker | | PT(=prothrombin
time) and PTT(=partial thromboplastin time) | measures
blood clotting manufacturing capability of liver |
| B-12 level | rule
out pernicious anemia | | liver
function tests: transaminases,alkaline phosphatase, lactic dehydrogenase
| these liver enzymes show whether
they leak into the blood and if bile ducts are blocked |
| platelets and white blood cells | decreases
in these cells indicate portal hypertension (see text) |
| hepatitis A,B,C, and D |
look for cause of chronic hepatitis, cirrhosis and risk for liver cancer |
| other tests | depending
on clinical situation | With hepatitis present
a further test can determine whether it is hepatitis B or C, both of which have
a higher risk of causing liver cancer. Finally, if platelets or white blood
cell counts are decreased, this is usually a sign that due to cirrhosis of the
liver there is obstruction of the flow of blood from the portal vein system and
the pressure is increased in it. Such a condition will lead to an enlargement
of the spleen, called "hypersplenism". The enlarged spleen filters out
platelets and white blood cells and they are missing in the blood stream, which
is shown in the test. The most common reason for cirrhosis of the liver is chronic
alcohol abuse. The next common cause of cirrhosis of the liver is chronic infection
with hepatitis B or C. There are newer serological tests that have been developed with
the goal in mind to develop a similarly specific and sensitive test for liver
cancer as the PSA test is in the case of prostate cancer. Radio-immuno-assays
for alpha-fetoprotein (AFP) are a promising first step. There are ethnic diffirences:
80%-90% are positive in Asian populations with liver cancer , but only 60%-70%
are positive in liver cancer patients in the US and Europe. Other tests are more
sensitive, but not specific enough. Only, when some of these tests are combined
with ultrasound investigations of the liver, will the sensitivity and specificity
reach 98% for liver cancer, not unlike in prostate cancer, where the combination
of rectal examination with a PSA blood test is recommended for screening. Other
diagnostic tests are done in the imaging department of the hospital or the X-ray
clinic. The first such test is an ultrasound
of the abdomen, gallbladder and liver, which serves as an initial screening test.
If this shows an abnormality in the liver, a CT
scan of the liver is then ordered, which can be improved in resolution
with by injecting contrast material. A socalled angioportography,
where contrast material is injected into an artery called "superior mesenteric
artery" that supplies the liver with blood, shows minute detail of the liver
tissue and is very useful as a test to look for the exact extent of the cancer
within the liver tissue. It also shows any local metastases. Alternatively
an MRI scan can also be ordered instead. However, people who
have metal foreign bodies in them from prior injuries are not allowed to undergo
MRI scanning, but can have CT scans. In the past before CT and MRI scanning arteriograms
were done where the pathological tumor vessels were depicted and used as a diagnostic
test. Occasionally this test is still done in special circumstances such as when
a partial resection of the diseased liver is planned. A nuclear
medicine liver
scan is done with Technetium 99m sulfur colloid
in a hospital. A variation of this using a rotating gamma camera allows for better
imaging with spacial orientation, called single-photon-emission CT (=SPECT
scan). These tests are all very useful to "round up the
cancer". But all the physician knows so far is that there is a biochemical
abnormality on the blood tests and that there is a shadow on the various images
of the imaging tests. But there is no histological proof (meaning a cell
test for proof of the presence of liver cancer) at this point to indicate that
indeed liver cancer is present. As I pointed out in the other cancer chapters,
cancer is a histological diagnosis. For this reason
a tissue sample has to be taken and sent to the pathologist for a definite tissue
diagnosis. This is done by either a percutaneous liver biopsy, an open
biopsy or a laparoscopic biopsy. However, it is wise to do all the other
tests mentioned above first, as there could be profuse bleeding in a case where
there is portal hypertension and where the blood is thinned due to missing clotting
factors. What approach the physician will finally take to obtain tissue for a
definite diagnosis of the patient's condition depends to a large extent on these
prior findings.
|
