The study is unique in that practical research on metastatic breast cancer treatment is rarely carried out on a large scale. The studies that are carried out tend to include only a small sample of the patient population (approximately 5%) and focus on testing new drugs. The remaining 95% of these studies tend to stay under the radar. This present study examined all patients with metastatic breast cancer in the southeast Netherlands – 815 in total – over a specific period of time. The added value of an observational study like this one is that it reveals how different sub-groups in patient populations with metastatic breast cancer respond to different treatments.

Subtype

The researchers found that a specific subtype, namely patients with hormone-sensitive breast cancer, often respond better if the treatment starts with hormone therapy instead of chemotherapy. Of the group that was first treated with hormone therapy, 33% more patients were alive two years later compared to the group that started with chemotherapy. These results could not be explained entirely by differences in prognoses: many of the patients who were first treated with chemotherapy had more extensive disease activity (metastases in the liver, bones and lungs), which made their prognosis inherently worse.

Clinical application

According to breast cancer specialist Vivianne Tjan-Heijnen of Maastricht UMC+, it's important to translate these findings into clinical applications as soon as possible. 'Not only patients with bone metastases respond well to hormone therapy, patients with metastases in organs such as the liver and lungs also show a positive response. Many of these patients are currently receiving chemotherapy, while they would respond much better to hormone therapy.' In addition, hormone therapy has fewer side effects than chemotherapy.

At present, there is no cure for patients with metastatic breast cancer. The purpose of the treatment is to prolong their life and improve and maximise their quality of life. 'A growing group of patients is living far longer,' adds Tjan-Heijnen. 'Many reach the five-year mark and some live for ten years or longer.'

Cooperation

This study on the treatment of metastatic breast cancer was a collaboration between eight hospitals in the southeast Netherlands known as the Zuidoost-Nederlands Borstkanker Consortium ('Southeast Netherlands Breast Cancer Consortium'). The study – lead by Professor Vivianne Tjan-Heijnen a medical oncologist at Maastricht UMC+ – was carried out by Dorien Lonnezoo, an internist-in-training at Máxima Medical Centre who received her PhD on 10 November from Maastricht University. Dr Wouter Dercksen, a medical oncologist at Máxima Medical Centre, and Dr Adri Voogd, an epidemiologist at Maastricht University, were also involved in the project.

The study was made possible with a grant from ZonMW and Roche.