GS6-01. Sestak I, Regan M, Dodson A, Viale G, et al. Integration of clinical variables for the prediction of late distant recurrence in patients with oestrogen receptor positive breast cancer treated with 5 years of endocrine therapy.

The authors of the study conclude that:

The CTS5 is a simple tool based on information that is readily available to all clinicians. It was more accurate in its prediction of DR risk in years 5-10 than the published CTS model. CTS5 was validated as highly prognostic for late DR in the independent BIG 1-98 study. The algorithm identified a subgroup of women with either node-negative disease or 1-3 positive nodes as having less than 1% per year risk of DR who could be advised of the limited value of extended endocrine therapy.

GS6-02. Goetz MP, O'Shaughnessy J, Sledge Jr. GW, Martin M, et al. The benefit of abemaciclib in prognostic subgroups: An exploratory analysis of combined data from the MONARCH 2 and 3 studies.

The authors of the study conclude that:

This exploratory analysis has provided data that could help optimize treatment strategies by identifying that patients with poor prognostic factors may receive greater benefit from the addition of abemaciclib to endocrine therapy.

GS6-03. Sparano JA, O'Neill A, Alpaugh K, Wolff AC, et al. Circulating tumor cells (CTCs) five years after diagnosis are prognostic for late recurrence in operable stage II-III breast cancer. See also webcast from press conference presentation

The authors of the study conclude that:

A single positive CTC assay in patients without clinical evidence of recurrence 5 years after diagnosis of stage II-III HR+, HER2- breast cancer provides independent prognostic information for late recurrence, providing proof of concept for using liquid-based biomarkers for late relapse risk assessment. These findings provide a foundation for further evaluation of this new risk assessment paradigm using CTC and other blood-based assays in this setting, and designing clinical trials to tailor therapeutic risk interventions.

GS6-04. Dubsky PC, Fesl C, Singer CF, Pfeiler G, et al. The EndoPredict score predicts residual cancer burden after neoadjuvant chemotherapy and after neoendocrine therapy in HR+/HER2- breast cancer patients from ABCSG 34.

The authors of the study conclude that:

Clinical standard of care separated ABCSG 34 patients into two HR+ cohorts with differing clinical features and treated distinctly with either NET or NCT: In women treated with neoadjuvant Letrozole a high molecular score indicated a very low possibility of endocrine response. In women clinically selected for neoadjuvant chemotherapy, a high EP score was associated with a higher probability of chemotherapy response and the low EP risk group outlined a group of women with very poor tumor response to NCT(NPV 100%).
In summary, EP low risk is associated with tumor response to endocrine treatment and predicts resistance in the chemotherapy group. NCT, especially to attain breast conservation in ER+/HER2-/EP low risk should be reconsidered.

GS6-05. Formisano L, Lu Y, Jansen VM, Bauer JA, et al. Gain-of-function kinase library screen identifies FGFR1 amplification as a mechanism of resistance to antiestrogens and CDK4/6 inhibitors in ER+ breast cancer.

The authors of the study conclude that:

These data suggest aberrant FGFR signaling is a mechanism of resistance to anti-ER therapies ± CDK4/6 inhibitors. We posit overexpression of cyclin D1 induced by both FGFR signaling and ER transcription plays a role in drug resistance. Based on these findings we propose ER+/FGFR1 amplified breast cancers are endocrine resistant and should be candidates for treatment with combinations of ER and FGFR antagonists. Accordingly, we have initiated a phase Ib trial of fulvestrant, palbociclib and erdafitinib in patients with antiestrogen resistant ER+/HER2-negative breast cancer with FGFR1-4 amplification.

GS6-06. Powell E, Shao J, Picon HM, Ge Z, et al. Identifying metastatic drivers in patient-derived xenograft models of triple negative breast cancer.

The authors of the study show that:

Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) was identified as a metastatic driver in this screen. CEACAM5 mRNA and protein levels were elevated in lung metastases relative to corresponding mammary gland tumors in mice. In addition, we demonstrated that CEACAM5 expression was upregulated in the lung metastases of breast cancer patients, and its expression inversely correlated with patient survival. Our data indicate that the metastatic function of CEACAM5 is to promote growth of breast tumors in the lung by inducing MET (mesenchymal to epithelial transition).

GS6-07. Litton J, Rugo HS, Ettl J, Hurvitz S, et al. EMBRACA: A phase 3 trial comparing talazoparib, an oral PARP inhibitor, to physician's choice of therapy in patients with advanced breast cancer and a germline BRCA mutation. See also webcast from press conference presentation

The authors of the study conclude that:

Single-agent TALA significantly prolonged PFS by BICR in HER2-negative aBC patients with a gBRCAmut compared to PCT; all key secondary efficacy endpoints demonstrated benefit with TALA, with a significant delay in time to deterioration in GHS/QoL. TALA was generally well tolerated with minimal non-hematologic toxicity and few AEs associated with treatment discontinuations.