Patient-specific Adaptive vs. Continuous Abiraterone or eNZalutamide in Metastatic Castration-resistant Prostate Cancer

• Status: Not yet recruiting
• Trial end date: 2027-08-01

Summary

Abiraterone and enzalutamide (AA/ENZ) are drugs which are being used to treat metastatic prostate cancer. These drugs are a form of additional hormonal therapy and have been used for many years. For most patients, these drugs work well and the prostate cancer stays under control for several months to years. In all patients, there will be a moment when the prostate cancer doesn't respond anymore to the treatment. This is called resistance. This leads to increasement of PSA, tumor growth on the CT-scan and/or bone scan or decline of condition. The investigators want to establish if it is possible to delay the development of resistance by using the drugs differently. It is now recommended to use AA/ENZ daily until the prostate cancer doesn't respond anymore to the treatment. During treatment, all cancer cells sensitive to treatment will die and all cells resistant for treatment will survive. Based on evolutionary principles, this might not be a wise strategy. The groups of resistant cancer cells will prevail and will grow faster and faster. This will lead to increasement of PSA, tumor growth on the CT-scan and/or bone scan or decline of condition. The investigators want to establish if it is better to not take the treatment drugs daily, but to pause the treatment on regular basis. The theory of the investigators is that, due to just in time pausing the treatment, a part of the treatment sensitive cells will remain alive. These treatment sensitive cancer cells will compete with the treatment resistant cells for limited space and nutrients. In this way, the treatment sensitive cancer cells prevent the accelerating growth of the treatment resistant cancer cells. Due to this phenomenon, the investigator hypothesis is the prostate cancer will respond longer to treatment. It will take longer until a new treatment is necessary or until a patients develops complaints. When the treatment is paused, patients might experience less side effects. It is easy to establish whether the prostate cancer responds to treatment by measuring PSA. Therefore, prostate cancer is suitable to this theory.

The study will include 168 men with metastatic castrate resistant prostate cancer in the Netherlands and Australia. Patients will be randomly 1:1 assigned between the control group and the experimental group. In the control group, patients will take the treatment with AA/ENZ every day until the prostate cancer doesn't respond anymore to the treatment. In the experimental group, patients will start with daily AA/ENZ until the PSA has declined for >50%. The treatment will then be paused and monthly PSA measurements will be performed. The treatment will be re-initiated when the PSA has increased to the level of before starting treatment. The treatment will be continued daily until the PSA has again dropped for >50%. This pause/restart cycle will be repeated until the prostate cancer doesn't respond anymore to the treatment.

The primary objective of the study is to investigate whether the patient-specific adaptive treatment with AA/ENZ leads to a longer time to treatment failure (TTTF) while on treatment, compared to daily treatment with AA/ENZ. Secondary/tertiary objectives are to compare time to PSA progression, time to radiological progression, quality of life and cost-effectiveness between the experimental and de control group.

• Phase: Phase 2

Details

• Lead Sponsor: dr. Tom van der Hulle
• Collaborators: Anticancer Fund, Belgium; Australian and New Zealand Urogenital and Prostate Cancer Trials Group
• Treatments: Abiraterone Acetate