CDK4/6 inhibitors can enhance the effectiveness of hormonal therapy in women with metastatic hormone receptor-positive breast cancer. Each year, around 1,700 women in the Netherlands are eligible for this treatment. The internationally treatment guidelines prescrib these inhibitors as a frontline treatment. However, it remained uncertain whether this approach yielded superior outcomes, despite the disadvantages of intensified treatment with increased side effects and hospital visits.
Hormonal therapy alone can be effective as well. Therefore, the key question was whether immediate initiation of the combination therapy yielded better results or if delayed administration was equally effective.
SONIA study
The SONIA study was initiated by oncologists Dr. Agnes Jager (Erasmus MC), Dr. Inge Konings (Amsterdam UMC - Cancer Center Amsterdam), and Prof. Dr. Gabe Sonke (Antoni van Leeuwenhoek / Netherlands Cancer Institute). The results were presented on Monday, June 5th, at the American Society of Clinical Oncology (ASCO) conference in Chicago.
In the study, all patients were treated with a CDK4/6 inhibitor. Participants were randomly assigned to one of two groups: one group received immediate CDK4/6 inhibitor combination treatment, while the other received it later when the initial hormonal therapy became less effective. The study design involved collaboration with the patient association (BVN) and numerous oncologists in the Netherlands. The SONIA study commenced in October 2017 and involved 1,050 patients across 74 hospitals in the Netherlands over a timespan of four years. The outcomes in both groups have now been compared.
Timing of combination therapy
Starting treatment later and administering CDK4/6 inhibitors for a shorter duration yield equally favorable outcomes for patients with advanced hormone receptor-positive breast cancer compared to prolonged combination treatment.
The period of disease control, known as progression-free survival, was found to be comparable between the two groups. However, patients who received immediate CDK4/6 inhibitor treatment used the medication on average for an additional 16.5 months compared to those who received it as a second-line treatment. Consequently, the former group experienced significantly more side effects, such as reduced blood cell counts, liver abnormalities, and fatigue. The smarter utilization of the CDK4/6 inhibitors resulted in 42% fewer side effects and saved approximately 35,000 euros per patient compared to the internationally established standard treatment.
The SONIA study concluded that treatment effectiveness was unaffected by the timing of CDK4/6 inhibitors.
For more information, contact Dr. Inge Konings, or read the press release (in Dutch) here.
Powered by collaboration
The SONIA study was initiated by oncologists Dr. Agnes Jager (Erasmus MC), Dr. Inge Konings (Amsterdam UMC Cancer Center Amsterdam), and Prof. Dr. Gabe Sonke (Antoni van Leeuwenhoek / Netherlands Cancer Institute) on behalf of the Dutch breast cancer oncologists collaborating in the Breast Cancer Research Group (BOOG), in close collaboration with the Dutch Breast Cancer Association (BVN), the Netherlands Comprehensive Cancer Organisation (IKNL), and the Institute for Policy and Management in Health Care (iMTA). The Dutch Ministry of Health, Welfare and Sport (VWS) and Health Insurers Netherlands (ZN) provided funding for this research.