Metastatic triple-negative breast cancer (TNBC) is associated with a poor prognosis, and the development of better therapeutics represents a major unmet clinical need. Although the mainstay of treatment of metastatic TNBC is chemotherapy, advances in genomics and molecular profiling have helped better define subtypes of TNBC with distinct biologic drivers to guide the therapeutic development of targeted therapies, including AKT inhibitors for PI3K/AKT-altered TNBC, checkpoint inhibitors for PD-L1–positive TNBC, and PARP inhibitors for BRCA1/2 mutant TNBC. This progress may ultimately convert TNBC from a disease traditionally defined by the absence of therapeutically actionable receptors to one that is defined by the presence of discrete molecular targets with therapeutic implications. Furthermore, antibody drug conjugates have emerged as an important therapeutic strategy to target genomically complex tumors that lack actionable oncogenes but have overexpressed actionable surface receptors such as trop-2. In this article, we discuss promising novel agents for advanced TNBC, some of which have been incorporated into current clinical practice, and others that will likely change the therapeutic landscape and redefine the TNBC terminology in the near future.
Novel Agents for Metastatic Triple-Negative Breast Cancer: Finding the Positive in the Negative
Neelima Vidula, Leif W. Ellisen, and Aditya Bardia
Pathologic Complete Response After Neoadjuvant Chemotherapy and Long-Term Outcomes Among Young Women With Breast Cancer
Laura Spring, Rachel Greenup, Andrzej Niemierko, Lidia Schapira, Stephanie Haddad, Rachel Jimenez, Suzanne Coopey, Alphonse Taghian, Kevin S. Hughes, Steven J. Isakoff, Leif W. Ellisen, Barbara L. Smith, Michelle Specht, Beverly Moy, and Aditya Bardia
Purpose: Breast cancer in young women is associated with an aggressive tumor biology and higher risk of recurrence. Pathologic complete response (pCR) after neoadjuvant therapy has been shown to be a surrogate marker for disease-free survival (DFS) and overall survival (OS), but the association between pCR and survival outcomes in young women with breast cancer is not well described. Methods: This study included women aged ≤40 years at diagnosis who received neoadjuvant chemotherapy (NAC) for stage II–III invasive breast cancer between 1998 and 2014 at Massachusetts General Hospital. Outcomes were compared between patients who achieved pCR (ypT0/is, ypN0) and those with residual disease. Results: A total of 170 young women were included in the analytical data set, of which 53 (31.2%) achieved pCR after NAC. The 5-year DFS rate for patients with and without pCR was 91% versus 60%, respectively (P<.01), and the OS rate was 95% versus 75%, respectively (P<.01). Among patients with pCR, no difference was seen in OS irrespective of baseline clinical stage (P=.6), but among patients with residual disease after NAC, a significant difference in OS based on baseline clinical stage was observed (P<.001). Conclusions: Our results suggest pCR after NAC is strongly associated with significantly improved DFS and OS in young women with breast cancer, and perhaps even more so than baseline stage. However, the significantly higher mortality for patients who did not attain pCR highlights the need for better therapies, and the neoadjuvant trial design could potentially serve as an efficient method for rapid triage and escalation/de-escalation of therapies to improve outcomes for young women with breast cancer.
Clinical Outcomes With Abemaciclib After Prior CDK4/6 Inhibitor Progression in Breast Cancer: A Multicenter Experience
Seth A. Wander, Hyo S. Han, Mark L. Zangardi, Andrzej Niemierko, Veronica Mariotti, Leslie S.L. Kim, Jing Xi, Apurva Pandey, Siobhan Dunne, Azadeh Nasrazadani, Avinash Kambadakone, Casey Stein, Maxwell R. Lloyd, Megan Yuen, Laura M. Spring, Dejan Juric, Irene Kuter, Ioannis Sanidas, Beverly Moy, Therese Mulvey, Neelima Vidula, Nicholas J. Dyson, Leif W. Ellisen, Steven Isakoff, Nikhil Wagle, Adam Brufsky, Kevin Kalinsky, Cynthia X. Ma, Joyce O’Shaughnessy, and Aditya Bardia
Background: Inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6i) are widely used as first-line therapy for hormone receptor–positive metastatic breast cancer (HR+ MBC). Although abemaciclib monotherapy is also FDA-approved for treatment of disease progression on endocrine therapy, there is limited insight into the clinical activity of abemaciclib after progression on prior CDK4/6i. Patients and Methods: We identified patients with HR+ MBC from 6 cancer centers in the United States who received abemaciclib after disease progression on prior CDK4/6i, and abstracted clinical features, outcomes, toxicity, and predictive biomarkers. Results: In the multicenter cohort, abemaciclib was well tolerated after a prior course of CDK4/6i (palbociclib)-based therapy; a minority of patients discontinued abemaciclib because of toxicity without progression (9.2%). After progression on palbociclib, most patients (71.3%) received nonsequential therapy with abemaciclib (with ≥1 intervening non-CDK4/6i regimens), with most receiving abemaciclib with an antiestrogen agent (fulvestrant, 47.1%; aromatase inhibitor, 27.6%), and the remainder receiving abemaciclib monotherapy (19.5%). Median progression-free survival for abemaciclib in this population was 5.3 months and median overall survival was 17.2 months, notably similar to results obtained in the MONARCH-1 study of abemaciclib monotherapy in heavily pretreated HR+/HER2-negative CDK4/6i-naïve patients. A total of 36.8% of patients received abemaciclib for ≥6 months. There was no relationship between the duration of clinical benefit while on palbociclib and the subsequent duration of treatment with abemaciclib. RB1, ERBB2, and CCNE1 alterations were noted among patients with rapid progression on abemaciclib. Conclusions: A subset of patients with HR+ MBC continue to derive clinical benefit from abemaciclib after progression on prior palbociclib. These results highlight the need for future studies to confirm molecular predictors of cross-resistance to CDK4/6i therapy and to better characterize the utility of abemaciclib after disease progression on prior CDK4/6i.