New clinical data show that the PARP inhibitor olaparib (Lynparza, AstraZeneca/Merck) also has a place in the treatment of early stage breast cancer with BRCA mutations, in addition to its already established role in the treatment of metastatic disease.
It’s a notable outcome given that at least 5% of all breast cancers are associated with BRCA1 or BRCA2 mutations, commented first author Andrew Tutt, MBChB, PhD, head of the Division of Breast Cancer Research at the Institute of Cancer Research and Guy’s Hospital, King’s College London, UK.
The new results come from the phase 3 OlympiA trial, which involved nearly 2000 women and showed that 1 year of adjuvant treatment with olaparib improved invasive and distant disease-free survival when used following adjuvant or neoadjuvant chemotherapy in patients with germline BRCA-mutated (gBRCAm) high-risk HER2-negative early breast cancer.
The study was highlighted at a press briefing ahead of the American Society of Clinical Oncology (ASCO) Annual Meeting 2021, where the data will be presented during a plenary session. The study will also be published simultaneously in The New England Journal of Medicine.
The “exciting findings” highlight the importance of genetic testing in appropriate patients to identify those who might benefit from this treatment, and could open the door to additional trials of adjuvant PARP inhibitor in other BRCA1– and BRCA2-associated cancers, ASCO president Lori J. Pierce, MD, commented during the press briefing.
“I think the implications are…one, it’s an early stage disease, and two, it’s a reminder that when you see a patient in clinic and you’re taking a history that you query them for family history,” Pierce told Medscape Medical News. “You try to find out which of these patients could have a mutation so we [can] refer them for testing, and if they have a mutation this will be a therapy that they would be able to get and will likely benefit from.”
Improved IDFS and DDFS
The double-blind OlympiA trial enrolled 1836 patients with gBRCAm and HER2-negative stage II-III breast cancer, including triple-negative or hormone receptor-positive disease with high risk of recurrence after completion of primary local treatment and adjuvant or neoadjuvant chemotherapy. Patients were randomized 1:1 to receive 1 year of continuous oral olaparib at a dose of 300 mg twice daily or placebo.
“Compared with placebo, patients receiving olaparib had a 42% reduction in the risk of the following events: local recurrence of breast cancer, metastatic recurrence of breast cancer, other new cancers, or death due to any cause,” Tutt said, describing the factors comprising the study’s primary endpoint of invasive disease-free survival (IDSF).
The hazard ratio for IDSF with olaparib versus placebo at a median follow-up of 2.5 years was 0.58, prompting the independent data monitoring committee to recommend unblinding the study at the time of the interim analysis.
At 3 years, 85.9% of patients in the olaparib group and 77.1% in the placebo group were alive and free from invasive disease, for a difference of 8.8%, Tutt said.
For the secondary endpoint of distant disease-free survival (DDFS), defined as the absence of metastatic breast cancer, new cancer, and death due to any cause, a highly statistically significant 43% reduction was observed with olaparib versus placebo (HR, 0.57). The survival curves separated early and remaining separated, with 3-year DDFS of 87.5% and 80.4%, for a 7.1% difference between the treatment and placebo group, he said.
“The secondary endpoint of overall survival is inevitably immature,” he added, noting that fewer deaths were nonetheless reported with olaparib at 3 years (3-year overall survival 92.0% vs 88.3%; HR, 0.68), although the difference did not reach statistical significance.
Adverse events observed in the trial were limited and manageable, and were consistent with known effects and product labeling, he said.
Grade 3 adverse events that occurred in more than 10% of patients receiving olaparib were anemia (8.7%), neutropenia (4.8%), leukopenia (3.0%), and fatigue (1.8%). Serious adverse events and adverse events of special interest, including myelodysplastic syndrome/acute myeloid leukemia, new primary malignancy, and pneumonitis, were not increased with olaparib; they occurred in 8.7% vs 8.4% and 2.6% vs 4.6% of patients in the treatment and placebo groups, respectively.
The findings have important implications for the future of breast cancer treatment, Tutt said.
Olaparib was already approved for use in the metastatic setting for gBRCAm HER2-negative breast cancer in 2018 on the basis of data from the pivotal OlympiAD trial, led by Mark E. Robson, MD, and colleagues.
In the high-risk early breast cancer setting, however, recurrence rates can be high even after chemotherapy, and novel adjuvant treatments have been lacking, Tutt commented.
The latest findings from OlympiA appear to represent “a major advance for the subset of patients who have inherited BRCA1 and BRCA2 mutations,” Robson said in an interview.
“The absolute differences — even with relatively short follow-up — in invasive disease-free survival are impressive, and even though overall survival is not yet statistically significant, one surely would be hopeful that with further follow-up a difference would emerge,” he said.
There was some suggestion, even in the OlympiAD trial, that the earlier patients with metastatic disease were treated with PARP inhibition, the more benefit they received, so it’s not surprising that research has moved into the early stage disease setting, he noted.
Future directions may include looking at different drug combinations as investigators did with some success in the BROCADE3 trial of the PARP inhibitor veliparib plus carboplatin and paclitaxel in metastatic gBRCAmut HER2-negative breast cancer – particularly if concerns about worsening myelosuppression when combining a PARP inhibitor and chemotherapy are attenuated with newer PARP inhibitors, he said.
“But for now, using [olaparib] after completion of conventional chemotherapy is the approach that makes the most sense,” he added.
Robson also noted that some smaller studies show “fairly dramatic pathologic complete response rates” with preoperative PARP inhibitor therapy. He said that “the idea of giving therapy even before surgery, perhaps as a de-escalation approach, is something that would be worth studying in the future.”
For now, it will be important to keep a close eye on whether there is any worsening of rates of second malignancies, especially leukemia, over time in the OlympiA trial participants.
“That was not seen in either the OlympiAD or EMBRACA study [another phase 3 study looking at PARP inhibition in advanced gBRCAmut HER2-negative breast cancer] in the metastatic setting, but obviously [the early breast cancer] population will be at risk for a longer period of time and we will need to see what the data are,” he said. “So far the results are all very encouraging, and this could lead to a new paradigm where we’re basically testing all women with breast cancer at the time of diagnosis to figure out whether or not this is an appropriate adjuvant treatment for them.”
The OlympiA trial was funded by the National Cancer Institute and AstraZeneca. Tutt has reported multiple relationships with companies including Inbiomotion, Medscape, Prime Oncology, Artios, AstraZeneca, Merck Serono, Pfizer, Merck KGaA, Roche/Genentech, Breast Cancer Now Charity, and Cancer Research UK. Robson has reported being an investigator for clinical trials of PARP inhibitors and receiving research grants (to his institution) from AstraZeneca, Merck, and Pfizer.
ASCO Annual Meeting 2021. ASCO Abstract LBA1. Presented June 3, 2021.
Sharon Worcester is an award-winning medical journalist at MDedge News, part of the Medscape Professional Network.
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