In the 5-year follow-up of the pivotal SOLO-1 trial in women with advanced ovarian cancer and a BRCA1/2 mutation, maintenance treatment with olaparib led to a doubling in progression-free survival. William H. Bradley, MD, presented these findings at the Society of Gynecologic Oncology (SGO) 2021 Virtual Annual Meeting on Women’s Cancer (Abstract ID 10520).
“The initial results were extremely positive. Now the 5-year follow-up demonstrates a statistically significant, sustained progression-free survival benefit that is appreciated across both higher-risk and lower-risk groups,” said lead author Dr. Bradley, a gynecologic oncologist at Froedtert and the Medical College of Wisconsin, Milwaukee.
The initial results were extremely positive. Now the 5-year follow-up demonstrates a statistically significant, sustained progression-free survival benefit that is appreciated across both higher-risk and lower-risk groups.— William H. Bradley, MD
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Olaparib is an oral inhibitor of poly [ADP-ribose] polymerase (PARP). SOLO-1 evaluated olaparib as a 2-year maintenance therapy in 391 women with newly diagnosed ovarian cancer harboring a germline or somatic BRCA1/2 mutation who had received platinum-based therapy as their initial treatment.
Data from this 5-year follow-up are the longest for any PARP inhibitor in the setting of maintenance after primary therapy, noted Dr. Bradley.
5-Year Findings
In the current analysis, median progression-free survival for the overall population was sustained far beyond the end of treatment: 56.0 months with olaparib vs 13.8 months with placebo (hazard ratio [HR] = 0.33, 95% confidence interval [CI] = 0.25–0.43). Five-year progression-free survival was 48% vs 21%, respectively.
“After 5 years, almost half of patients [treated with olaparib] were progression-free, vs 20% [treated] with placebo. This is the only PARP inhibitor for which efficacy has been demonstrated beyond the completion of therapy,” indicated Dr. Bradley. “These results further support the use of maintenance olaparib as a standard of care for women with newly diagnosed advanced ovarian cancer and a BRCA mutation, and suggest the possibility of long-term remission or even cure for some patients.”
The study’s invited discussant, Deborah Armstrong, MD, Professor of Oncology and Director of the Breast and Ovarian Surveillance Service at Johns Hopkins Medicine, reiterated Dr. Bradley’s optimism.
“Maybe we can start to use ‘the C word,’” she said. “Not cancer—but the ‘cure’ word—for some of these patients.”
Benefit in High-Risk and Low-Risk Patients
Additionally, the researchers analyzed subgroups of patients based on their risk of disease progression. Compared to those treated with placebo, olaparib recipients had better 5-year progression-free survival regardless of their initial risk.
Higher-risk disease comprised stage IV patients; stage III patients who received initial neoadjuvant chemotherapy and underwent interval cytoreduction; and stage III patients with gross residual disease after initial cytoreductive surgery. Lower-risk disease included stage III patients who underwent optimal cytoreductive surgery and had no gross residual disease.
For the higher-risk subgroup, median progression-free survival was 40.6 months with olaparib and 11.0 months with placebo (HR = 0.35). For the lower-risk subgroup, this outcome was not reached with olaparib and was 21.9 months with placebo (HR = 0.38).
“Secondary data outcomes also support the observed benefit in progression-free survival,” said Dr. Bradley. Time to second progression or death was reduced by 54% with olaparib, and time to subsequent therapy was reduced by 54% as well.
“Importantly, we saw no new safety signals—including no additional cases of myelodysplastic syndrome or acute myeloid leukemia during this follow-up period,” said Dr. Bradley. The incidence of these secondary malignancies remained at less than 1.5%.
Disclosure: Dr. Bradley has served in an advisory or consulting role for and received travel support from Inovio.
