ESMO 2019: Dr. O'Shaughnessy Highlights Progress in Breast Cancer

Joyce A. O'Shaughnessy, MD, co-chair of Breast Cancer Research, chair of Breast Cancer Prevention Research at Baylor-Sammons Cancer Center, Texas Oncology, chair of The US Oncology Network, and 2016 Giant of Cancer Care^® in Community Outreach, discusses updates in breast cancer presented at the 2019 ESMO Congress.

Data from the phase III MONARCH 2 trial, examining the combination of abemaciclib (Verzenio) and fulvestrant (Faslodex) versus fulvestrant and placebo in patients with hormone receptor (HR)—positive, HER2-negative advanced breast cancer, showed a median overall survival (OS) of 46.7 months with the addition of fulvestrant versus 37.3 months with placebo plus fulvestrant (HR, 0.757; 95% CI, 0.606-0.945; P =.0137). Considering the use of endocrine therapy alone had limited survival benefit in this setting, O'Shaughnessy considers the MONARCH 2 findings a big advance.

The phase III MONALEESA-3 trial demonstrated that the combination of ribociclib (Kisqali) and fulvestrant reduced the risk of progression or death by approximately 28% versus placebo and fulvestrant in postmenopausal patients with HR—positive, HER2-negative advanced breast cancer, regardless of whether patients received the treatment in the frontline or early relapse/second-line settings. Additionally, at a median follow-up of 39.4 months, the median OS was not reached in the ribociclib arm and was 40.0 months in the placebo arm (HR, 0.724; 95% CI, 0.568-0.924; P = .00455). These data indicate that CDK4/6 inhibitors should be used in practice, especially in the frontline setting for patients with metastatic disease, says O'Shaughnessy.

Moreover, data from the phase II monarcHER trial showed that, in advanced HR—positive, HER2-positive breast cancer, adding the CDK4/6 inhibitor abemaciclib and endocrine therapy to trastuzumab (Herceptin) improved progression-free survival (PFS) compared with trastuzumab and chemotherapy. Median PFS was 8.32 months versus 5.69 months in patients treated with the triplet versus the combination, respectively. Patients in a third randomized cohort looking at abemaciclib and trastuzumab without fulvestrant had similar outcomes to those in the trastuzumab/chemotherapy control group. Based on these data, O'Shaughnessy believes the approval of the triplet is likely.

Additionally, a phase II trial found that the investigational CDK4/6 inhibitor trilaciclib improved survival in patients with metastatic triple-negative breast cancer, despite failing to meet a safety-related primary endpoint. Median OS improved by more than 60% in patients who received either of the two dosing regimens of trilaciclib plus gemcitabine and carboplatin. However, the addition of trilaciclib to chemotherapy did not reduce the frequency and duration of severe neutropenia compared with chemotherapy alone. Additionally, PFS and objective response rate did not improve with the addition of trilaciclib. Given the survival signal reported in the trial, O'Shaughnessy is interested in launching a phase III trial.

With the emergence of new treatment options, optimal sequencing has become a big question in the field and requires further research to find an answer. According to O'Shaughnessy, there has been an abundance of new data in breast cancer, making this an exciting time in the field.