ASCO 2018 highlights: metastatic breast cancer

This article reviews the clinically most relevant presentations at the American Society of Clinical Oncology (ASCO) annual meeting 2018 on the topic of metastatic breast cancer. In the randomized placebo-controlled phase3 trial MONALEESA-3, testing ribociclib vs. placebo in combination with fulvestrant in postmenopausal women or men with hormone receptor-positive (HR+) and HER2-negative (HER2-) advanced breast cancer (ABC), an increase of median progression-free survival (PFS) from 12.8months to 20.5months by the addition of the CDK4/6 inhibitor was reported (HR 0.59; P>0.01). Taselisib, an alpha specific PI3K inhibitor, was tested in combination with fulvestrant in pretreated HR+/HER2- ABC patients with PIK3CA mutations in the placebo-controlled phase3trial SANDPIPER. PFS was significantly longer (7.4months vs 5.4months; HR 0.70, P<0.01) but severe adverse events were more frequent (32% and 9%) in the taselisib group. In triple-negative breast cancer, the AKT inhibitor capivasertib (AZD5363) was combined with paclitaxel as first-line treatment in the placebo-controlled phase2trial PAKT. In patients with altered PIK3CA, AKT1 or PTEN, median PFS increased from 3.7months to 9.3months (HR 0.30; two-sided P=0.01). No treatment effect was shown in the non-altered group. The most common adverse events attributed to capivasertib were diarrhea, fatigue and stomatitis. Results of two phaseItrials of trastuzumab antibody-drug conjugates (ADCs) indicated HER2 as anon-oncogenic surface target in breast cancer patients expressing HER2.