Approximately 100 men per year are diagnosed with breast cancer in the Netherlands, compared to more than 14,000 women.
In the vast majority of breast cancers, both in men and women, the tumour is hormone-sensitive.
This means that hormones, like estrogen, influence the DNA, causing the tumour to grow and eventually to spread.
Anti-hormonal therapy, aimed at blocking the female hormone estrogen, is therefore also often part of the treatment for men.
Often with effect but also with stressful side effects.
However, there was not yet a scientific basis for giving men the same treatment as women.
Researchers, led by Wilbert Zwart, have now mapped the hormonal function over the entire tumour DNA for the first time and compared men and women.
Their findings are published in Nature Communications.
The first conclusion was that by far most of the breast tumours in men and women are barely distinguishable from each other.
This provides a scientific basis for the current practice of giving men and women the same anti-hormonal therapy.
But as with women with hormone-sensitive breast cancer, there are also men whose cancer still comes back despite the treatment.
This group is therefore likely to benefit from a different or supplementary approach.
And it is precisely in this group of men that the DNA profiles of the tumour appear to be gender-specific.
Wilbert Zwart said “We had already seen that very specific patterns in women are predictive of the course of the disease. In patients with a less favourable course of the disease, other sites of the DNA are active under the influence of hormones. That says something about the therapy sensitivity of each individual tumour and this knowledge is essential when looking for a personalised therapy. In men, we also see specific patterns that are different than in women. If we are to work towards a personalised therapy for men, the selection of medicines may, therefore, have to be slightly different. But a lot of research is still needed for this.”