Impact of a CDK4/6 Inhibitor plus Fulvestrant on Overall Survival in Patients with Breast Cancer

Researchers continue to investigate the effect of cyclin-dependent kinase 4/6 inhibitors (CDKIs) that have been approved by the US Food and Drug Administration (FDA) for use as first- or second-line treatment of hormone receptor–positive, HER2-negative advanced or metastatic breast cancer in combination with endocrine therapy.

Previously reported results have shown a consistent benefit from the addition of these oral targeted CDKI agents to endocrine therapy; these pooled analyses have shown improved progression-free survival of patients in certain subgroups.

At the American Society of Clinical Oncology 2021 annual meeting, Gao and colleagues reported the pooled overall survival (OS) results of patients treated with CDKI in combination with fulvestrant.

From 3 phase 3 randomized breast cancer trials of a CDKI plus fulvestrant that had been submitted to the FDA for marketing applications, the investigators pooled individual patient data from 1948 patients. At least 1 dose of a CDKI or placebo, plus fulvestrant, was administered to all patients included in the analysis. Data from all pooled patients, first-line treated patients, and second-line treated patients, as well as later treatment settings, were reviewed and analyzed.

Further subgroup analyses of OS were conducted based on breast cancer histology, Eastern Cooperative Oncology Group performance status, progesterone receptor status, site of metastases, race, and de novo metastatic presentation. Results of these OS analyses all supported the addition of CDKI to fulvestrant. While the estimated OS favored fulvestrant monotherapy in the younger cohort consisting of patients who were aged <40 years, the sample size was very small (N = 89), so the investigators cautioned putting too much weight in the interpretation.

While these results are still in exploratory and at hypothesis-generating stages, Gao et al concluded that both across all pooled patients and within most subgroups of interest, emerging data support the combination of CDKIs with fulvestrant based on a conferred and consistent survival benefit.

Source:

Gao JJ, Cheng J, Prowell TM, et al. Overall survival in patients with breast cancer treated with a CDK 4/6 inhibitor plus fulvestrant: a U.S. Food and Drug Administration pooled analysis. Presented at: American Society of Clinical Oncology 2021 Annual Meeting, June 4-8. Abstract 1055.