Check Up #9 - Markers of cancer

Cancers can be detected through the presence, in the tumours or bodily fluids, of so-called molecular biomarkers – in other words, of biological molecules (proteins, genes, etc.) found in blood or tissues that are a sign that a person has cancer. One well-known cancer biomarker is the PSA protein, whose rapid rise in the blood may indicate the presence of prostate cancer. 

Biomarker molecules have many potential applications in oncology, two of which are their use in prognosis (determining the likely outcome of a patient’s disease) and the prediction of a patient’s cancer response to a given treatment. 

A prognostic biomarker informs about a likely cancer outcome (recurrence, progression, death) independently of the treatment received. Examples of prognostic biomarkers are the PSA level at the time of prostate cancer diagnosis, and the presence of mutations in a gene called PIK3CA in the tumours of women with so-called HER2–positive metastatic breast cancer. (Mutations in this gene lead to defects in a protein that can cause cells to multiply uncontrollably.) Yet another prognostic biomarker for breast cancer is Mammaprint, based on the 70 most important genes associated with breast cancer recurrence (or relapse).

A predictive biomarker gives information about treatment benefits. More to the point, that means there is a difference in a given treatment’s effect depending on the presence or the absence of the biomarker. So a predictive biomarker allows for choosing and planning the most adequate treatment. The estrogen receptor (ER), the progesterone receptor (PR) and the human epidermal growth factor receptor 2 (HER2) are the most commonly used biomarkers in clinical practice for making treatment plans for breast cancer patients.

Clinically useful cancer biomarkers are sometimes hard to come by. That is why, in part, it is so hard to make an early diagnosis of pancreatic cancer, which could save many patients’ lives. The fact is that, although some potential markers have been identified, they still have to prove their clinical usefulness.

Which brings us to the importance of rigorous evaluation of predictive biomarkers. As Fátima Cardoso, director of the Champalimaud Foundation’s Breast Unit, explains, “a wrongly evaluated biomarker would lead to wrong treatment decisions”. This could not only deprive patients of potentially more effective treatments, but even do them harm.

Sources

https://www.ncbi.nlm.nih.gov/
https://www.cancer.gov/
https://www.nytimes.com/
https://ascopubs.org
https://www.sciencedirect.com/journal/seminars-in-diagnostic-pathology
https://febs.onlinelibrary.wiley.com/journal/18780261

By Ana Gerschenfeld, Health & Science Writer of the Champalimaud Foundation.

Reviewed by: Professor António Parreira, Clinical Director of the Champalimaud Clinical Center.