Webinar Triple Negative Breast Cancer: Understanding Treatment Resistance and New Treatment Options Triple-negative breast cancer (TNBC) is highly resistant to treatment and remains the most challenging subtype of cancer to treat, particularly once it has progressed. There is a need to educate participants regarding the growing understanding of crosstalk between growth factor signaling and ER pathways and the implications of this crosstalk for treating patients with endocrine-resistant tumors.