MUNICH – Olaparib maintenance therapy significantly reduces risk of disease progression or death in women with BRCA-mutated advanced ovarian cancer who respond to chemotherapy, according to results from the SOLO-1 trial.
The benefit from olaparib was compelling; compared with placebo, more than twice the number of women were alive and without disease progression after 3 years.
Current guidelines recommend olaparib for relapsed ovarian cancer, but the SOLO-1 results support first-line application, said lead author,at the European Society for Medical Oncology Congress.
“We believe that the SOLO-1 data really prompts a change in the standard of care for women with advanced ovarian cancer who harbor a BRCA mutation,” said Dr. Moore of the Stephenson Cancer Center at the University of Oklahoma in Oklahoma City.
Olaparib () currently is approved for relapsed ovarian cancer regardless of mutation status, but poor outcomes suggest that this intervention is given too late – many patients relapse, and when they do, most do not survive.
“Although the majority of ... patients have no evidence of disease after [chemotherapy], approximately 70% have a relapse within the subsequent 3 years,” the investigators wrote in an article simultaneously published in the. “Recurrent ovarian cancer is typically incurable, with most patients receiving multiple additional lines of treatment before ultimately dying from the disease.”
Poly (ADP-ribose) polymerase (PARP) inhibitors, such as olaparib, are well matched for BRCA-mutated tumors; they interfere with DNA repair, thereby exploiting repair deficits conferred by BRCA mutations. One in six women with advanced ovarian cancer exhibits a BRCA mutation, so eligible patients are relatively common.
The phase 3, placebo-controlledinvolved 391 patients with advanced ovarian cancer who had a complete or partial response to platinum-based chemotherapy. Patients exhibited mutations in BRCA1, BRCA2, or both (BRCA1/BRCA2). After chemotherapy, patients were randomized to receive either olaparib 300 mg twice daily or placebo (in a 2:1 ratio).
The primary endpoint was progression-free survival (PFS) determined by imaging; MRI or CT was performed at baseline and every 3 months for up to 3 years, with 6-month intervals thereafter. Patients who had no disease progression at 2 years halted therapy, whereas patients with disease progression were allowed to continue olaparib if desired.
The 3-year follow-up period (median, 40.7 months) revealed a dramatic benefit from olaparib; the PFS rate was 60% for olaparib, compared with 27% for placebo (P less than .001). This represents a 70% reduction in risk of disease progression or death. Because of the magnitude of prolonged survival, median PFS could not be determined; however, estimates suggest that olaparib adds 3 years without disease progression.
Dr. Moore noted that these benefits were consistent regardless of stage or level of response to chemotherapy (partial vs. complete). “Everyone benefits,” she said. “It really looks like an all subgroup-beneficial regimen.”
Still, questions of long-term benefit remain unanswered. “It’s too early to know what [the extended PFS] means long term,” Dr. Moore said. “We hope that it means we’ve converted a larger fraction of patients to cure, and that’s what you’re seeing with the flattening of the survival curve, but it took us 3 years just to get to this point, so how long will it take us to comment on overall survival? It’s a good problem to have, but it’s going to remain to be seen.”
As therapy was discontinued at 2 years, and yet patients remained progression free after 3 years, researchers also are left wondering about mechanisms of action. “Has olaparib eradicated all the disease?” asked, member of the ESMO faculty and professor of medical oncology at University College London. “Or is something else happening, such as an immune response that’s taking over when you stop the drug? We don’t know the answer to that, but it’s an intriguing question and one that we need to follow up on.”
Safety data from SOLO-1 were comparable with previous olaparib trials. Overall, olaparib was well tolerated, with 21% of patients experiencing serious adverse events. The most common serious adverse event was neutropenia (7%).
SOLO-1 was sponsored by AstraZeneca and Merck. The authors reported financial affiliations with Clovis, Tesaro, Mateon, Merck, and others.
SOURCE: Moore et al. N Eng J Med. 2018 Oct 21. .