Real-World Evaluation of Disease Progression After CDK 4/6 Inhibitor Therapy in Patients With Hormone Receptor-Positive Metastatic Breast Cancer.

BACKGROUND: Cyclin-dependent kinase 4/6 inhibitors (CDKi) have changed the landscape for treatment of patients with hormone receptor positive, human epidermal growth factor receptor 2-negative (HR+/HER-) metastatic breast cancer (MBC). However, next-line treatment strategies after CDKi progression are not yet optimized. We report here the impact of clinical and genomic factors on post-CDKi outcomes in a single institution cohort of HR+/HER2- patients with MBC. METHODS: We retrospectively reviewed the medical records of patients with HR+/HER2- MBC that received a CDKi between April 1, 2014 and December 1, 2019 at our institution. Data were summarized using descriptive statistics, the Kaplan-Meier method, and regression models. RESULTS: We identified 140 patients with HR+/HER2- MBC that received a CDKi. Eighty percent of patients discontinued treatment due to disease progression, with a median progression-free survival (PFS) of 6.0 months (95% CI, 5.0-7.1), whereas those that discontinued CDKi for other reasons had a PFS of 11.3 months (95% CI, 4.6-19.4) (hazard ratio (HR) 2.53, 95% CI, 1.50-4.26 [P = .001]). The 6-month cumulative incidence of post-CDKi progression or death was 51% for the 112 patients who progressed on CDKi. Patients harboring PTEN mutations pre-CDKi treatment had poorer clinical outcomes compared to those with wild-type PTEN. CONCLUSION: This study highlights post-CDKi outcomes and the need for further molecular characterization and novel therapies to improve treatments for patients with HR+/HER2- MBC.

Impact of TP53 mutations in Triple Negative Breast Cancer.

Identifying triple negative breast cancer (TNBC) patients expected to have poor outcomes provides an opportunity to enhance clinical management. We applied an Evolutionary Action Score to functionally characterize TP53 mutations (EAp53) in 96 TNBC patients and observed that EAp53 stratification may identify TP53 mutations associated with worse outcomes. These findings merit further exploration in larger TNBC cohorts and in patients treated with neoadjuvant chemotherapy regimens.

Prognostic/predictive markers in systemic therapy resistance and metastasis in breast cancer.

Breast cancer is a highly heterogeneous group of diseases posing a significant challenge in biomarker-driven research and the development of effective targeted therapies. Especially the treatment of metastatic breast cancer poses even more challenges, as we still lose more than 42,000 women and men each year in the United States alone. New biological insight helps to improve breast cancer treatment through early detection, adaptation to chemotherapy resistance, and tailoring to find the right size of care. This review focuses on existing and new areas of predictive biomarkers under development to tailor the management of breast cancer and the application of integrative approaches that have resulted in the promising candidate biomarker discovery. Furthermore, we review new methods to detect metastatic progression using imaging, and blood-based assays. We hope to increase the attention and awareness of a new generation of therapeutic development strategies in metastatic breast cancer.

Development of the PARP inhibitor talazoparib for the treatment of advanced BRCA1 and BRCA2 mutated breast cancer.

INTRODUCTION: BRCA1 and BRCA2 (BRCA1/2) mutation breast cancers constitute an uncommon, but unique group of breast cancers that present at a younger age, and are underscored by genomic instability and accumulation of DNA damage. Talazoparib is a potent poly(ADP-ribose) polymerase (PARP) inhibitor that exploits impaired DNA damage response mechanisms in this population of patients and results in significant efficacy. Based on the results of the EMBRACA trial, talazoparib was approved for the treatment of patients with advanced germline BRCA1/2 mutant breast cancer. AREAS COVERED: In this review, the authors highlight the relevant clinical trials of talazoparib, as well as, safety, tolerability, and quality of life considerations. They also examine putative response and resistance mechanisms, and rational combinatorial therapeutic strategies under development. EXPERT OPINION: Talazoparib has been a major advance in the treatment of germline BRCA1/2 mutation breast cancer with both clinical efficacy and improvement in quality of life compared to standard cytotoxic chemotherapy. To date, the optimal sequencing of talazoparib administration in the metastatic setting has not yet been established. A deeper understanding of response and resistance mechanisms, and more broadly, the DNA repair pathway, will lead to additional opportunities in targeting this pathway and open up therapeutic indications to a broader patient population.

Phase Ib/II single-arm trial evaluating the combination of everolimus, lapatinib and capecitabine for the treatment of HER2-positive breast cancer with brain metastases (TRIO-US B-09).

BACKGROUND: Improving outcomes for patients with human epidermal growth factor 2-positive (HER2+) central nervous system (CNS) metastases remains an unmet clinical need. This trial evaluated a novel combination of everolimus, lapatinib and capecitabine for this disease. METHODS: Patients with trastuzumab-pretreated, HER2+ breast cancer brain metastasis without prior therapy with a mammalian target of rapamycin (mTOR) inhibitor were eligible. Patients received lapatinib and everolimus daily (continuously) and capecitabine twice daily (d1-14) in 21-d cycles. The primary endpoint was the 12-week CNS objective response rate (ORR). Secondary endpoints included safety, progression-free survival (PFS), overall survival (OS), best CNS ORR and extra-CNS ORR. RESULTS: A total of 19 participants were enrolled and treated with ⩾1 dose of the study drug. The median age was 58.5 years, the median number of therapies for metastatic breast cancer was 2.5 (0-11). Pretrial, 74% of participants had received prior lapatinib, capecitabine or both. A total of 63% had received previous CNS radiation or surgical resection and CNS radiation. The maximum tolerated doses were lapatinib at 1000 mg, everolimus at 10 mg, and capecitabine at 1000 mg/m2. Phase II proceeded with capecitabine at 750 mg/m2 due to better tolerability. The most common grade 3/4 adverse events were mucositis (16%), diarrhea, fatigue, and hypokalemia (11% each). Of 11 participants evaluable for 12-week CNS ORR, 3 (27%) had partial response and 7 (64%) had stable disease. The best CNS ORR in eligible participants was 28% (5/18). The median PFS and OS were 6.2 and 24.2 months, respectively. CONCLUSIONS: This novel triplet combination of lapatinib, everolimus, and capecitabine is well tolerated and yielded a 27% response rate in the CNS at 12 weeks in heavily pretreated participants. Larger studies are warranted to further evaluate this regimen. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01783756. Registered 05 February 2013, https://clinicaltrials.gov/ct2/show/NCT01783756.

Nicotine does not enhance tumorigenesis in mutant K-ras-driven mouse models of lung cancer.

Smoking is the leading cause of preventable cancer deaths in the United States. Nicotine replacement therapies (NRT) have been developed to aid in smoking cessation, which decreases lung cancer incidence. However, the safety of NRT is controversial because numerous preclinical studies have shown that nicotine enhances tumor cell growth in vitro and in vivo. We modeled NRT in mice to determine the effects of physiologic levels of nicotine on lung tumor formation, tumor growth, or metastasis. Nicotine administered in drinking water did not enhance lung tumorigenesis after treatment with the tobacco carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Tumors that develop in this model have mutations in K-ras, which is commonly observed in smoking-related, human lung adenocarcinomas. In a transgenic model of mutant K-ras-driven lung cancer, nicotine did not increase tumor number or size and did not affect overall survival. Likewise, in a syngeneic model using lung cancer cell lines derived from NNK-treated mice, oral nicotine did not enhance tumor growth or metastasis. These data show that nicotine does not enhance lung tumorigenesis when given to achieve levels comparable with those of NRT, suggesting that nicotine has a dose threshold, below which it has no appreciable effect. These studies are consistent with epidemiologic data showing that NRT does not enhance lung cancer risk in former smokers.