Hormone-lowering therapies, also called endocrine therapies, have long been used after oncological surgery to reduce the risk of breast cancer cells spreading, but it’s not clear how long the treatment provides protection after that. Many cancers are at risk of recurring for a short time, usually within a few years.
However, for patients with hormone-sensitive breast cancer, the risk of recurrence often extends over several decades. About 80 percent of all people with breast cancer have estrogen receptor-positive breast cancer, which means that estrogen stimulates the cell to divide so that the tumor grows. Since many women are diagnosed with breast cancer at a relatively young age, knowing the long-term effect of treatment is very important.
Less risk of distant metastases
Building on a previous study, conducted between 1990 and 1997, researchers at Karolinska Institutet have now investigated the benefit of long-term treatment of hormone-reducing therapy in 584 premenopausal women with estrogen-receptor-positive breast cancer. The study also included a control group that did not receive any hormone-lowering treatment.
We can see that after 20 years, the risk of distant metastases, that is, spread to other organs, was reduced among women who received hormone-lowering therapy with tamoxifen, goserelin, or a combination of the two, compared to women who received hormone-lowering therapy. She has not received any hormone-lowering treatment, says Anneli Johansson, a postdoctoral fellow in the Department of Oncology Pathology, Karolinska Institutet.
It is possible to predict future risks
In recent years, researchers have also analyzed patients’ tumors from the previous study using modern technology. For example, they investigated several markers of breast cancer, such as estrogen receptors and progesterone receptors, as well as tumor gene expression using a so-called genetic risk fingerprint.
The signature measures the activity of 70 different genes, which boils down to the degree of risk. It makes it possible to predict the future development of cancer cells at an early stage and thus classify patients into low and high genomic risk, respectively.
It is important to adapt the treatment
Tumors of patients with a high genetic risk usually have a higher rate of cancer growth. Therefore these patients are at risk of relapse early and therefore require more aggressive treatment, for example with goserelin, which rapidly and effectively reduces estrogen levels. On the other hand, patients with less aggressive disease appear to be at risk of relapse in the long term. In these cases, tamoxifen appears to provide better protection, Anneli Johansson says.
Although the study is relatively small, it highlights the importance of individualized treatment for hormone-sensitive breast cancer. For some patients, more aggressive treatment may be necessary for survival, while for others a milder treatment may be sufficient, reducing side effects and providing a better quality of life. However, follow-up studies are needed before major changes in treatment recommendations can be implemented.
To understand the long-term risks and benefits of treatment and the differences in relation to age, we will now apply machine learning methods to analyze images of breast cancer tumors to further investigate differences between tumors, says Linda Lindstrom, research group leader in the Department of Oncology and Pathology, Karolinska Institutet.
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