Poor Prognostic Markers Predict for Abemaciclib Benefit in Patients With Breast Cancer

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This analysis was undertaken to determine whether patient and disease characteristics can predict which patients will benefit from abemaciclib.
This analysis was undertaken to determine whether patient and disease characteristics can predict which patients will benefit from abemaciclib.
The following article features coverage from the San Antonio Breast Cancer Symposium (SABCS) 2017 meeting. Click here to read more of Cancer Therapy Advisor's conference coverage.

Patients with poor prognostic factors may benefit from adding abemaciclib to their treatment regimens, according to a post-hoc pooled analysis of data from patients with hormone receptor–positive, HER2-negative advanced breast cancer. The analysis was presented at the 2017 San Antonio Breast Cancer Symposium.1

According to Matthew P. Goetz, MD, of the Mayo Clinic in Rochester, Minnesota, these results could help to optimize treatment strategies for patients with poor prognoses.

“These exploratory analyses from over 1000 patients treated in MONARCH 2 (ClinicalTrials.gov Identifier: NCT02107703) and MONARCH 3 (ClinicalTrials.gov Identifier: NCT02246621) demonstrated that all subgroups benefited from the addition of abemaciclib to endocrine therapy,” Dr Goetz said. “Abemaciclib in combination with endocrine therapy offered the largest benefit (objective response rate [ORR] and progression-free survival [PFS]) in patients with clinical characteristics that make prognosis more concerning. The largest improvements were in patients with liver metastases, progesterone receptor–negative tumors, or high-grade tumors.”

Abemaciclib is a twice-daily oral selective inhibitor of CDK4 and 6. In combination with fulvestrant or aromatase inhibitors, it is generally tolerable and has demonstrated clinical efficacy against hormone receptor–positive, HER2-negative advanced breast cancer. This analysis was undertaken to determine whether patient and disease characteristics can predict which patients will benefit from abemaciclib.

The authors conducted patient subgroup analyses to examine the candidate prognostic variables' associations with ORR and PFS. They identified several variables as prognostic of PFS, and entered these into a stepwise multivariate model stratified by treatment arm and study. Prognostic variables included performance status, tumor grade, progesterone receptor status, liver metastases, and bone-only metastases.

ORR benefit was associated with negative progesterone receptor status, the presence of liver metastases, and tumor grade.

While all subpopulations benefited from the addition of abemaciclib to endocrine therapy regardless of prognosis, substantial benefit of abemaciclib was observed in poor prognosis subgroups, characterized by large increases in PFS (hazard ratios [HRs], 0.4 to 0.5) and ORR (over 30%),” the authors stated.

Women with the shortest treatment-free interval after adjuvant endocrine therapy benefit most from abemaciclib, Dr Goetz added.

Read more of Cancer Therapy Advisor's coverage of the San Antonio Breast Cancer Symposium (SABCS) 2017 meeting by visiting the conference page.

Reference

  1. Goetz MP, O'Shaughnessy J, Sledge Jr. GW, et al. The benefit of abemaciclib in prognostic subgroups: An exploratory analysis of combined data from the MONARCH 2 and 3 studies. Oral presentation at: 2017 San Antonio Breast Cancer Symposium; December 5-9, 2017; San Antonio, TX.

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