Do men with mCRPC need to stay on ADT along with their abiraterone acetate?

On and off over the past few years your sitemaster has raised the question of whether there is any real clinical benefit to maintaining men on standard androgen deprivation therapy (ADT) once they become castrate resistant and are switched to treatment with newer drugs like abiraterone acetate (Zytiga) or enzalutamide (Xtandi).

Apparently a group of German researchers decided it was time to address this question, so they organized a pilot study (the SPARE trial) to look into it.

Ohlmann et al. recently reported on the design of the SPARE trial in a paper in BioMed Central. The full text of the paper is available on line, so people can get most of the details there.

Basically the SPARE trial was designed to randomize about 60 to 70 chemotherapy-naive patients with progressive, asymptomatic or mildly symptomatic, metastatic, castrate-resistant prostate cancer (mCRPC) to treatment with

  • Either abiraterone acetate + prednisone alone (and stopping their prior ADT)
  • Or abiraterone acetate + prednisone + an LHRH agonist (i.e., the current standard of care)

For the purposes of this study, patients can be included even if their only metastatic disease is a lymph node metastasis, but such a metastasis must be at least 2 cm in diameter.

The study then tracks patients for 12 months from the start of their therapy, and the primary study endpoint will be radiographic progrogression-free survival (rPFS) after 12 months on therapy. In  other words, the primary question being asked is whether the men who have stopped their prior ADT and are treated with abiraterone acetate alone progress any faster than the men who stay on their ADT along with the abiraterone acetate.

The research group is also tracking a number of other factors — such as the patients’ PSA levels, objective response rates (based on the RECIST criteria), Bone Scan Indexes, and biochemical levels of luteinizing hormone (LH), luteinizing hormone-releasing hormone (LHRH), follicle stimulating hormone (FSH), testosterone (T), and dihydrotestosterone (DHT).

We look forward to hearing the early results of this pilot trial. We have been advised that the trial was fully enrolled as of May this year, and so the research team will be able to start the final analysis of the trial results in May 2018. Prof. Ohlmann and his colleagues are hoping to be able to present the results of this trial at the annual meeting of the European Society for Medical Oncology (ESMO) in October next year (appropriately enough, at Munich in Germany).

Editorial note: The “New “Prostate Cancer InfoLink thanks Prof. Carsten Ohlmann of the Department of Urology, Saarland University, for his prompt response to our questions about the current status of the trial and when we might expect to hear any results.

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