Why is my tumour marker not measured at every visit?

Tumour markers are not stable values; they fluctuate depending on certain circumstances. For example, an infection or a recent operation will increase your tumour marker. Testing your tumour marker too often shows small fluctuations, while only the overall picture of stabilisation or a steady rise or fall is important.

The main way to monitor the evolution of your disease is a radiological examination, such as a CT or MRI scan. The tumour marker is considered an indicator to check in between whether a treatment seems to be working. It is also used during follow-up to assess whether the disease is still under control. However, decisions are almost always made on the basis of a scan.