Tumor Marker CA 19-9

We have deliberately included the topic of tumour markers as a main topic in this issue. Time and again we are asked in consultations and group meetings:

• What are tumour markers?
• Are they important?
• What do they mean?

We at TEB recommend all affected persons to have the tumour marker checked monthly, once it has been established that it is positive; in order to better monitor the course of the illness. Not all doctors share this view - we are aware of that.
From the feedback we get, we know that affected persons and their relatives watch the tumour marker to check if it moves - whether it goes up, moves up and down or stands still. But, to do that, it has to be drawn on a monthly basis.
Affected persons are often told that the costs for a monthly blood sample extraction are too high and would not be paid for by the health insurance, whereupon they often pay for the additional costs themselves.

Many people tell us that they are not scared of the results, contrary to what many doctors claim. They are more afraid that the increase may not be noticed, and that their treating oncologist will not be able to intervene in time and possibly change the chemotherapy. They are scared of losing valuable time.

In the case of tumour markers, the measured values are strongly dependent on the test kit used by the respective laboratory.

While we can argue about whether individual affected persons can cope with and need to know the results of the tumour marker, we are, however, of the opinion that the tumour marker is meaningful and important. It is a fact that the tumour marker often shows a result more quickly than imaging methods and so indicates possible recurrences or metastases earlier.   Regular checking of the tumour marker CA 19/9 (for pancreatic carcinoma) has been incorporated into the medical guidelines.

Tumor marker

The importance and value of tumour markers are often subject to great uncertainty and misunderstandings. Therefore an explanation of tumour markers is following - what are they and what significance do they have.

Measurable substances

Tumour markers are measurable substances in blood, urine or tissue – mostly proteins, peptide etc. which occur in a high concentration when cancer is present. These substances are either produced by the cancer itself or as a reaction of the body to the cancer. Rises in the results of tumour markers can, however, also indicate other illnesses (with few exceptions), for example, infections, so that a diagnosis cannot be made only on the basis of the results of the tumour marker. This is called low specificity.

However, tumour markers are important for monitoring the course of disease, for the evaluation of cancer therapy and for the assessment of relapses (recurrence). Another advantage of tumour markers is that they indicate the presence of a tumour or a relapse much earlier than imaging methods. Some Tumour markers, e.g. Calcitonin, PSA, AFP, have a relatively high organ specificity (= indication of a tumour in a certain organ), this organ specificity is however less with other tumour markers (e. g. CA 19-9). The relevant tumour marker for our affected persons, CA 19-9, is neither tumour nor organ specific, so shows higher results with infections or other types of cancers (liver carcinoma, gall bile duct carcinoma, stomach cancer etc.).

In this respect the tumour marker can give wrong “positive” results on the one hand ( a rise due to infections, cell damage caused by radiation or chemotherapy, slower metabolism during renal insufficiency, liver dysfunction) as well as wrong negative results (synthesis blocked by Lewis- a/b negative persons, inadequate secretion, tumour mass too small etc.) The determination of tumour markers is therefore only one component within the diagnosis and the evaluation of the results of a tumour marker should always be viewed within the context of clinical examination, imaging methods (ultra-sound, CT, MRT) and other laboratory tests. However, there are now newer tumour markers, which are not organ-specific but very tumour-specific. They could perhaps also be consulted.

However, the determination of the respective tumour markers is also necessary if, for example, there is a clinical or imaging suspicion of cancer, as well as before, during and after tumour therapy (surgery, radiation, chemotherapy) or for follow-up control. Especially during chemotherapy, the tumour marker can provide a decisive indication of whether the chemotherapy is successful (tumour marker drops) or unsuccessful (tumour marker rises), and should therefore be changed. In this respect, the tumour markers should always be determined at regular intervals during chemotherapy in order to be able to change chemotherapy if necessary in time in case of failure of the previous therapy.
The sensitivity of the tumour marker CA 19-9 lies between 70 - 95% with a diagnostic specificity (= target reliability) of 70 - 90%. However, there is no direct correlation between CA 19-9 concentration and tumour mass.

The measured values of tumour markers are strongly dependent on the test kit used by the respective laboratory. This becomes problematic if different laboratories with different test kits are used in the course control. It is therefore always important to ensure that the values are determined by the same laboratories with comparable test kits wherever possible.

Further developments of tumour markers

In addition to tumour markers, genetic diagnostics are now also being used. If a tumour shows certain genes (e. g. HER 2 gene in breast cancer), this is of crucial importance for course and choice of therapy. In addition, scientists are working intensively on the further development of tumour markers. “Liquid Biopsy ", the blood-based nucleic acid analysis for the detection of tumour cells or tumour DNA in the blood, etc. is only mentioned here. To date, however, these methods are still purely experimental.

Joachim Horcher