SOLO1 Update Confirms Long-Term PFS Benefit Of Olaparib Maintenance

Author: By Lynda Williams, Senior medwireNews Reporter 

medwireNews: Updated findings from the SOLO1 trial show that the benefits of a 2-year maintenance olaparib regimen in patients with newly diagnosed BRCA1/2-mutated advanced ovarian cancer persist after treatment has ended. 

The median 5-year progression-free survival (PFS) duration in the post-hoc analysis was 56.0 months with olaparib 300 mg twice daily versus 13.8 months for placebo, giving a significant hazard ratio (HR) for progression or death of 0.33, similar to the previously reported 3-year HR of 0.30, the researchers write in The Lancet Oncology.  

The international phase III trial included patients with BRCA1/2-mutated advanced, high-grade serous or endometrioid ovarian cancer who had achieved a partial or complete response to platinum-based chemotherapy. 

The 260 patients who were randomly assigned to receive maintenance olaparib continued treatment for longer than the 131 controls (median 24.6 vs 13.9 months), were less likely to stop treatment within 2 years (43 vs 71%), and more likely to continue their trial regimen beyond 2 years (10 vs 2%). 

At data cutoff in March 2020, the olaparib and control groups had been followed up for a median 4.8 and 5.0 years, respectively, during which time a corresponding 45% and 76% of patients had experienced progression or death.  

The 5-year PFS rates were 48% with olaparib and 21% with placebo, with 5-year second PFS rates of 64% and 41%, respectively. The time to second disease progression or death was also significantly longer with olaparib than placebo, with median durations of not reached versus 42.1 months (HR=0.46). 

And among patients who had a complete clinical response to platinum chemotherapy, the median recurrence-free survival duration was significantly longer in those given olaparib than placebo, at not reached versus 15.3 months (HR=0.37). 

In addition, Susana Banerjee, from The Royal Marsden NHS Foundation Trust and Institute of Cancer Research in London, UK, and co-investigators say that exploratory analysis indicated a “consistent” PFS benefit with olaparib when assessing patients by higher (stage IV or stage III with residual disease or interval surgery) or lower clinical risk, or by the presence of a BRCA1 versus BRCA2 mutation. 

The safety analysis at the 5-year follow-up was in line with the initial findings from the SOLO1 trial and there were no new reports of myelodysplastic syndrome or acute myeloid leukaemia in the extended follow-up period. New primary malignancies occurred in 3% of olaparib-treated and 4% of placebo-treated patients. 

Susana Banerjee and co-authors say that the “substantially greater” improvement in PFS with olaparib versus placebo highlights “the importance of early use of maintenance olaparib therapy.” 

They continue: “Furthermore, given that ovarian cancer is typically incurable once relapse occurs, our findings suggest an increased possibility of cure for newly diagnosed patients with a BRCA mutation and for their life expectancy to approach that of the age-adjusted general population; however, longer follow-up is needed for evaluation of survival.” 

Reference 

Banerjee S, Moore KN, Colombo N, et al. Maintenance olaparib for patients with newly diagnosed advanced ovarian cancer and a BRCA mutation (SOLO1/GOG 3004): 5-year follow-up of a randomised, double-blind, placebo-controlled, phase 3 trial. Lancet Oncol; Advance online publication 26 October 2021. DOI: https://doi.org/10.1016/S1470-2045(21)00531-3