[GS1-01] Landscape of the breast tumour microenvironment at single-cell resolution  

Swarbrick A, Wu SZ, Roden D, Al-Eryani G, et al.

The authors conclude that: This data provides by far the most extensive insights into the cellular landscape of breast cancer and will reveal new biomarkers and opportunities for stromal- and immune-based therapy.

[GS1-02] Towards a human breast cell atlas  

Seth TK, Bai S, Hu M, Sei E, et al.

The authors conclude that: These data provide a valuable reference for the research community and will provide new insights into how normal cell types are transformed in the tumor microenvironment to promote or inhibit the progression of breast cancer.

[GS1-03] Crosstalk between osteoblasts and breast cancer cells alters breast cancer proliferation through multiple mechanisms 

Bussard KM, Shupp AB, Kolb AD, Mukhopdhyay D.

The authors conclude that: Our late-breaking data suggest that OBs produce factors that suppress metastatic BCC growth. Much less attention has been given to OB interactions with tumor cells at sites of bone metastasis due to observations that OB populations are reduced at sites of advanced osteolysis. However, we propose that OBs may be valuable endogenous targets to aid in the restoration of bone deposition and suppression of metastatic BrCa growth in the niche in concert with therapeutic drugs to kill the cancer cells. Our data suggest there is a population of OBs that demonstrate a functional role in retarding metastatic BCC growth; a property capable of exploitation. Moreover, restoration of the OBs' ability to deposit new bone would lead to better quality of life and increased time of survival for bone metastatic BrCa patients where bone loss is found. For these reasons, OBs and EOs are suitable candidates for therapeutic targeting and will open new avenues for retarding the growth of BrCa bone metastases.

[GS1-04] IMpassion130: Efficacy in immune biomarker subgroups from the global, randomized, double-blind, placebo-controlled, phase III study of atezolizumab + nab-paclitaxel in patients with treatment-naïve, locally advanced or metastatic triple-negative breast cancer

Emens LA, Loi S, Rugo HS, Schneeweiss A, et al.

The authors conclude that: Exploratory efficacy analyses from IMpassion130 suggest consistency between local and central ER/PR/HER2 testing and that PD-L1 IC is the most robust predictive biomarker for selecting untreated mTNBC pts who benefit from A-nabPx.

Hollern DP, Xu N, Mott KR, He X, et al.

The authors conclude that: Together, these data point to key immune biomarkers of response to anti-PD1/anti-CTLA4 therapy; we have further developed a genomic predictor of ICI response using our murine models and will test this on a human TNBC data set. Lastly, this GEMM system provides a rich RNA-seq resource, and new immune-activated models for TNBC, which uncovered a key role for B-cells and CD4+ T-cells in response to ICI therapies.

Desmedt C, Richard F, Majjaj S, Pingitore J, et al.

The authors conclude that: This is to our knowledge the largest metastatic ILC series in which matched P and M samples were interrogated, revealing several genomic alterations, some of which potentially targetable, driving disease progression and endocrine resistance.

[GS1-07] The genomic landscape of 501 metastatic breast cancer patients

Angus L, Wilting SM, van Riet J, Smid M, et al.

The authors conclude that: WGS of this unique cohort of patients with MBC shows a genetic make-up roughly similar to primary BC, but does show subtype-specific enrichment of selected driver mutations in metastatic disease. This study provides better insight into the tumor biology of MBC potentially improving management of these patients.

[GS1-08] Genomic characterisation of metastatic breast cancer

Andre F, Filleron T, Ng C, Bertucci F, et al.

The authors conclude that: the present study, based on 629 patients, identifies 11 driver gene alterations and four mutational processes enriched in HR+/Her2- metastatic breast cancers. Final results on 800 patients will be presented.

Nikhil Wagle, MD, Dana-Farber Cancer Institute, Boston, MA

[GS1-10] Phase III study of trastuzumab emtansine (T-DM1) vs trastuzumab as adjuvant therapy in patients with HER2-positive early breast cancer with residual invasive disease after neoadjuvant chemotherapy and HER2-targeted therapy including trastuzumab: Primary results from KATHERINE