• Mario Campone, Seock-Ah Im, Hiroji Iwata, Mark Clemons, Yoshinori Ito, Ahmad Awada, Stephen Chia, Agnieszka Jagiełło-Gruszfeld, Barbara Pistilli, Ling-Ming Tseng, Sara Hurvitz, Norikazu Masuda, Javier Cortés, Michele De Laurentiis, Carlos L Arteaga, Zefei Jiang, Walter Jonat, Sylvie Le Mouhaër, Banu Sankaran, Laurence Bourdeau, Mona El-Hashimy, Dalila Sellami, and José Baselga.
• Centre René Gauducheau, Institut de Cancérologie de L'Ouest, Saint Herblain, France. Electronic address: Mario.Campone@ico.unicancer.fr.
• Eur. J. Cancer. 2018 Nov 1; 103: 147-154.

BackgroundBuparlisib, a pan-phosphatidylinositol 3-kinase (PI3K) inhibitor, plus fulvestrant in the BELLE-2 study significantly improved progression-free survival (PFS) in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer.Patients And MethodsIn this phase III study, patients were randomised 1:1 to buparlisib (100 mg/day; continuously in 28-day cycles) or placebo, plus fulvestrant (500 mg on cycle 1 day 15, and day 1 of subsequent cycles). Overall survival (OS) was assessed in the overall population and patients with known PI3K pathway status (both had shown significant PFS improvements). OS by PIK3CA status in circulating tumour DNA (ctDNA) was an exploratory end-point.ResultsA total of 2025 patients were screened for eligibility between 7th September 2012 and 10th September 2014, and 1178 received fulvestrant (500 mg) during a run-in phase; 31 discontinued. Of 1147 patients (median age 62 years), 98% had the Eastern Cooperative Oncology Group performance status ≤1, and 59% had visceral disease. Median follow-up from randomisation to data cut-off (23rd December 2016) was 37.6 months. Median OS trended in favour of the buparlisib arm in the overall population (33.2 versus 30.4 months; P = 0.045) and among patients with known PI3K pathway status (30.9 versus 28.9 months; P = 0.144); neither outcome was statistically significant. Median OS also trended in favour of buparlisib among patients with PIK3CA-mutant ctDNA (26.0 versus 24.8 months). Grade III/IV adverse events with ≥10% difference between the buparlisib versus placebo arms were elevated alanine aminotransferase (26% versus 1%), elevated aspartate aminotransferase (18% versus 3%) and hyperglycemia (15% versus <1%).ConclusionsOS results were in favour of buparlisib plus fulvestrant versus placebo plus fulvestrant; however, there is no statistical significance and more frequent grade III/IV adverse events were reported. Use of more selective PI3K inhibitors might provide the greatest clinical benefit and tolerable safety profile in this setting. Further evaluation of the predictive benefit of PIK3CA-mutant ctDNA is warranted.Trial Registration NumberNCT01610284.Copyright © 2018 Elsevier Ltd. All rights reserved.

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