Abiraterone Acetate Plus Prednisone Shows ‘Potential Activity’ After Inadequate ADT Response

Metastatic prostate cancer patients with an inadequate response to androgen deprivation therapy may benefit from abiraterone acetate plus prednisone

medwireNews: Abiraterone acetate plus prednisone might be an option for metastatic prostate cancer with a poor response to initial androgen deprivation therapy (ADT), suggest the S1014 trial researchers.

The patients, all of whom had a PSA of at least 4.0 ng/mL after 6–12 months of initial ADT, were given abiraterone acetate 1000 mg/day plus prednisone 5 mg twice daily; participants who had a falling PSA level at the time of enrolment were also allowed to continue with their original anti-androgen agent.

The phase II trial investigators admit that the primary endpoint of a prostate-specific antigen (PSA) level of 0.2 ng/mL or less was achieved in only five (13%) of the 40 participants and thus did not meet the prespecified number for success in six patients.

A further 33% achieved a partial response, defined as a PSA reduction below 4.0 ng/mL but above the 0.2 ng/mL threshold, while 40% had no PSA response and 15% were not assessed and assumed to be unresponsive.

However, the researchers say the “potential activity” of the combination in this poor prognosis group means “further testing of its upfront use in patients with metastatic prostate cancer should be considered.”

In particular, they describe the median overall survival of 25.8 months and the median progression-free survival of 17.5 months as “encouraging compared with historical controls”.

“The therapy was generally well tolerated, without any clear signal of any unexpected adverse effects”, write Thomas Flaig, from the University of Colorado in Aurora, USA, and co-authors.

There was one report of a grade 4 alanine aminotransferase elevation and one case of grade 4 rectal haemorrhage. Grade 3 events were reported in 11 patients, including hypertension, elevated aspartate aminotransferase, hyperglycaemia, hypokalemia, and nausea and vomiting.

They conclude: “Ongoing and future studies should evaluate the use of next-generation hormonal agents in the upfront setting and integration of such agents with chemotherapy for these patients.”

Reference

Flaig TW, Plets M, Hussain MHA, et al. Abiraterone acetate for metastatic prostate cancer in patients with suboptimal biochemical response to hormone induction. JAMA Oncol; Advance online publication 30 March 2017. doi:10.1001/jamaoncol.2017.0231

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