In my waiting room, I often hear patients comparing their cancer markers with one another. "Wah, my cancer marker is so much higher than yours," some would lament.
This comparison among patients is inappropriate. Some patients may have a small cancer with very high cancer markers and the converse is also true. One should use the markers for comparison only with oneself.
The reason is that the same cancer, both in type and stage, can produce different amounts of protein.
Cancer markers are proteins produced by the cancer cells, which are detected and measured in the blood.
When used correctly, these markers tell us a lot. For example, cancer markers are very useful in following up the progress of patients with known cancer. The marker is often, but not always, a good indicator of whether the treatment is working. It is also useful in helping to detect cancer recurrence.
The use of cancer markers to follow up patients with breast cancer is not a standard recommendation. Some would consider this "over-servicing" of the patient.
I beg to differ.
There are so many anecdotes of patients who have benefited from routine testing of cancer markers.
One such story is that of Madam Indriati, who has been under my care since 2001. She had stage two breast cancer with spread to her axillary lymph nodes.
This group of patients tends to have a poorer long term outlook as the risk of recurrence tends to be higher than those whose cancer has not spread to the lymph nodes.
In her case, eight years have passed and all has been well. She still sees me once in four months. When she saw me in January, all was well except that one of her cancer markers called CA19-9 was about 100 (the normal being less than 37).
There are many cancer marker types and CA19-9 is a notoriously sensitive yet non-specific marker.
In the course of my work, I see many patients and get calls from many colleagues asking for advice on what to do with seemingly healthy individuals who have raised CA19-9 levels.
When this level is very high - in the thousands - one would seriously consider the possibility of a cancer in the pancreas or some other part of the gastrointestinal tract.
Even so, one patient, a good friend of my father's who I have been seeing for almost two years, has no cancer even though his CA19-9 has gone as high as 2,000. It eventually settled down to a normal level without treatment.
This cancer marker can also be raised when there is an infection or inflammation. It is not uncommon to find it raised in patients with arthritis (inflammation of the joints) or in patients with bowel problems.
Anyway, I reassured Madam Indriati that there was nothing to worry about and ordered a repeat test when she came back for her regular follow-up last month.
I can, of course, order a barrage of tests for any patient with raised CA19-9, to try to explain why the marker is raised.
However, that would incur unnecessary cost as the large majority of patients would have no significant findings.
But to my horror, Madam Indriati's CA19-9 rose to more than 1,000 when I saw her last month. I requested a positron emission tomography-CT scan (which can pinpoint the location of the cancer) immediately and she was found to have cancer in the liver.
The scan showed that this was a solitary lesion in the liver. The cancer was successfully removed by a liver surgeon several days later.
It was eventually confirmed to be a cancer cell thatoriginated from the bile ducts within the liver.
In other words, this was a form of primary liver cancer and the surgery was potentially curative.
There is no question that the finding of raised cancer markers can lead to tests and more tests, when there may in fact be nothing wrong with the patient.
That is why it is important to assess each patient individually and exercise good clinical judgment on how far to go with the tests.
If I were to have a raised cancer marker, I would definitely want to find out about it and give myself the option of just monitoring it or carrying out further tests.
In Madam Indriati's case, we are simply thankful we detected a new cancer at a stage when there is the chance of a cure.
Almost certainly, I shall be watching her cancer markers like a hawk.
Dr Ang, the medical director of Parkway Cancer Centre, has been treating cancer patients for 23 years. In 1996, he was awarded Singapore's National Science Award for his outstanding contributions to medical research.
