What blood trace element levels can reveal about breast cancer and treatment outcomes

Authors: The team of the Fundamental and Applied Research Projects (FLPP) study ‘Prospective study of trace elements in breast cancer risk and treatment response’

Breast cancer is the most common form of malignant tumour among women worldwide, yet it is still not entirely clear why two women with a similar genetic predisposition to breast cancer can have very different outcomes: one develops breast cancer, while the other does not. Genes can tell us a great deal about cancer risk, but they do not explain everything. Lifestyle, diet and environmental factors may also play a role.

Researchers at Rīga Stradiņš University (RSU) are currently investigating one piece of this complex puzzle. A new study* will measure the blood levels of six elements: selenium, copper, zinc, arsenic, lead and cadmium. The researchers aim to discover whether levels of these elements are associated with breast cancer risk and treatment outcomes.

Can trace elements be classified as “good” or “bad”? At first glance, it might seem possible to divide the six elements under investigation into two groups. Studies have linked arsenic, cadmium and lead to an increased risk of breast cancer, while evidence suggests that selenium and zinc may be associated with better treatment outcomes or survival. However, such a simple distinction would be misleading.

Selenium – more is not always better

Selenium is one of the most extensively studied trace elements. In a study conducted in Poland involving 546 women with breast cancer, blood samples were collected after diagnosis but before treatment. In that study, normal selenium levels were associated with better long-term survival: five years after diagnosis, 82.5% of patients in the group with normal serum selenium levels were still alive, compared with 68.1% in the group with lower selenium levels.

In addition, when it comes to selenium, the principle that “more is better” does not apply. Research suggests that selenium levels in the body, diet and genetic factors may all play a role. The available evidence therefore does not support the conclusion that taking selenium supplements reduces breast cancer risk or improves treatment outcomes.

Taken together, these findings show why researchers need to assess not only each element individually, but also the relationships between them.

Why balance matters as much as quantity

For copper and zinc, the balance between the two elements in the body may be as important as their individual levels. Studies conducted in Sweden and Poland found that patients with a lower serum copper-to-zinc ratio had better long-term outcomes following a breast cancer diagnosis. In the Polish study, 82.1% of patients in the group with the lowest copper-to-zinc ratio were alive ten years after diagnosis, compared with 58.3% in the group with the highest ratio.

However, the available evidence is not yet sufficient to establish what copper-to-zinc ratio might protect against breast cancer.

Why this study is needed in Latvia

Previous studies in this field have involved populations in countries such as Sweden and Poland, and findings from other countries cannot necessarily be applied directly to people in Latvia.

Environmental conditions also vary between regions of the world. For example, European soils contain considerably less selenium than those in North America and Asia.

The new RSU study will measure the levels of selenium, copper, zinc, arsenic, lead and cadmium in the blood, while simultaneously collecting information on the participants' lifestyle and diet. The study aims to recruit 400 women newly diagnosed with breast cancer, 200 healthy women carrying inherited variants in the BRCA1 or BRCA2 gene that increase breast cancer risk, and 400 healthy women for comparison.

Although the findings so far are promising, they are not yet sufficient for trace element levels to be used in routine clinical practice to predict breast cancer risk or treatment outcomes in a given population. Studies that follow women’s health over a longer period are therefore needed. The new study may help determine how relevant the associations observed to date are specifically for women in Latvia.

Why the control group matters

To determine whether the differences in trace element levels observed among patients are associated with breast cancer, researchers also need data from women who do not have the disease. Comparing trace element levels in women with breast cancer and those without it may reveal differences that would not be apparent if only patients were studied. Information on diet and lifestyle will also help researchers account for other factors that may influence trace element levels. The researchers plan to invite women to join the control group soon. Details of how to apply and participate will be published later.

Why taking part in cancer research is important

Every new medicine, medical technology or algorithm can only be introduced into clinical practice because patients and healthy women around the world have agreed to take part in research. We therefore thank all the women who have responded to calls for participation and whose involvement has helped improve cancer treatment outcomes here in Latvia.

Over the past 20 years, approximately 40,000 patients and people without cancer have taken part in various studies conducted by the RSU Institute of Oncology and Molecular Genetics. The research team is also grateful to the 200 women who have already agreed to take part in this trace element study, complete a questionnaire about their daily diet and provide blood samples. Thanks to the participants, researchers can collect the data needed to address the study’s central question: are blood levels of trace elements associated with breast cancer risk and treatment outcomes?

The study ‘Prospective study of trace elements in breast cancer risk and treatment response’ (No. lzp-2025/1-0414) is being carried out under the Fundamental and Applied Research Projects programme administered by the Latvian Council of Science.

Read the full version of the article (in Latvian) on the Latvian public media news portal LSM.lv