Tumor markers are just what they sound like, a way to mark a tumor. In other words, they can tell us, ideally, what a tumor is doing: growing or not growing.
You noticed I said, Ideally.
Exactly… there’s nothing ideal about the current tumor marker tests. But they’re all we’ve got right now and they are definitely better than nothing.
Let me explain the science behind them to make it a little clearer.
Most, if not all, cancers produce substances into our bodies. Some cancers produce proteins, some actually shed tumor cells. These substances can be found in either our blood, our urine, or in other body tissues. Tumor markers are tests to determine how much of these substances are floating around our body. The more tumor substance found in the body then it stands to reason, that the more active the cancer is. “Ideally.”
Unfortunately these tests are still a long way from being foolproof. There can be false positives and false negatives. Many other factors can alter the marker results, so most doctors use them as just one test among many to stage cancers and determine growth and advancement of the disease.
The most common tumor marker for pancreatic cancer is the CA 19-9. It was first developed to detect colon cancer, but has been found to also be sensitive for pancreatic cancer.
Ca 19-9 is a substance that is released into the blood by the pancreatic cancer cells. This marker test is performed by taking a small amount of blood and testing it.
A normal Ca 19-9 in a healthy individual can range from 0-37 U/ml. So anything higher than 37 should prompt a more thorough investigation. It sounds like a perfect screening test doesn’t it? Unfortunately, by the time blood levels are high enough to be consistently detected by this blood test, the cancer is usually in advanced stages. So, no, not a great screening test.
On the other hand, the Ca19-9 test is fairly accurate in evaluating how a patient is responding to the cancer treatment or chemotherapy. If the chemo is knocking back the cancer and slowing the growth, then the tumor won’t be shedding so much of the substance, resulting in lower Ca 19-9 figures. If the chemo is not working then obviously the tumor will be more active, shedding more substance, and having higher Ca 19-9 numbers.
One word of caution here. Don’t get caught in the trap of worrying over every spike in the marker test. Doctors generally are looking for trends over a period of time rather than one elevated test to determine success or failure of your treatment.
A second word of caution. There are a small number of people whose pancreatic cancers do not shed the Ca 19-9 substance. Their tumor marker test for Ca 19-9 will always come back low, irregardless of whether the cancer is growing or gone. If you fall into this group, your doctor will most likely opt for more frequent CT scans and evaluations to monitor your progress.
And finally, a third word of caution. (see what I mean? This tumor marker test is definitely not foolproof!). It’s important to know that the Ca 19-9 test can be elevated for other reasons besides pancreatic cancer. Among these are gallstones, pancreatitis (inflammation of the pancreas, not related to cancer), cirrhosis, and cholecystitis.
Mom is a good example of the erratic behavior of the Ca19-9 test. Her numbers have gone up and down like a roller coaster. Her initial tumor marker test was 404. Chemotherapy and radiation have gotten the test down at one point to a low of 84. But it’s been as high as 1474, after a 2 month hiatus from chemo due to a nasty gall bladder surgery. Her doctor uses the CA 19-9 test mainly to see how treatment is progressing. So far, the Gemzar keeps knocking the tumor marker back down. When the marker doesn’t respond to the chemo, we will know it’s time to move on to another treatment.
We’re thankful there are ways of monitoring mom’s cancer, even if the marker test is a tad unreliable. Certain cancers don’t even have that.
Funny, a year ago, being thankful for a blood test for cancer wasn’t even on my radar screen. So glad it was on the researcher’s. Who knows? In another decade maybe we’ll be light years ahead in detecting and monitoring pancreatic cancer. Praying that it will be so…
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