ASCO 2019: TOPARP-B Trial of Olaparib in Castration-Resistant Prostate Cancer
Posted: Friday, June 28, 2019
For men with metastatic castration-resistant prostate cancers that have DNA repair defects, olaparib seems to exhibit antitumor activity and delay disease progression, according to the results of the phase II TOPARP-B trial, presented at the 2019 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago (Abstract 5005). BRCA1/2-aberrant tumors were most sensitive to olaparib, but responses were confirmed in patients with other alterations as well, concluded Joaquin Mateo, MD, PhD, of The Institute of Cancer Research and The Royal Marsden National Health Society (NHS) Foundation Trust, London, and colleagues.
“We have shown that by testing for DNA repair mutations, we can select those patients with a high chance of responding well and for a long time to the targeted drug olaparib,” said Johann S. De Bono, MD, PhD, also of The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, in an ASCO press release. “The next phase of the trial is now underway and, if the results look as good as we hope, we should see olaparib starting to reach the clinic for men with prostate cancer in the next couple of years.”
The authors enrolled 98 patients with metastatic castration-resistant prostate cancer with detected DNA damage repair genes. Patients received either 400 mg or 300 mg of olaparib twice daily.
The overall response rate for patients who received 400 mg was 54%, and for those in the 300-mg group, it was 37%. After a median follow-up of 17.6 months, the overall median progression-free survival in each cohort was 5.4 months. Overall, 47% of patients responded to olaparib, with a drug-delayed disease progression of a median of 5.5 months.
For patients with BRCA1/2-mutated prostate cancer, 80% responded to olaparib. Subgroup analyses also indicated a 57% response rate among patients with mutations in PALB2, 37% for those with mutations in ATM, and 25% for patients with mutations in CDK12.
Disclosure: The study authors’ disclosure information may be found at coi.asco.org.
