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, said 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.
The new results come from the phase 3 OlympiA trial, which involved nearly 2,000 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, 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, said 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,” Dr. Pierce said in an interview. “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 1,836 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,” Dr. 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%, Dr. 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 (hazard ratio [HR], 0.57). The survival curves separated early and remained 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.