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Esteva Explains State of Genomic Testing in Breast Cancer

Danielle Bucco
Published: Tuesday, Aug 22, 2017

Francisco J. Esteva, MD, PhD
Francisco J. Esteva, MD, PhD
Physicians must continue to develop an understanding of breast cancer tissue and plasma to personalize medicine and deliver the optimal treatment to their patients, says Francisco J. Esteva, MD, PhD, who spoke on genomic testing at the 16th Annual International Congress on the Future of Breast Cancer® (East).

In an interview during the meeting, Esteva, a professor in the Department of Medicine at NYU Langone Medical Center, discussed the clinical implications of genomic testing for patients with metastatic breast cancer.

OncLive: What are the clinical implications of genomic testing in breast cancer?

Esteva: There are different technologies that are being used to profile both primary and metastatic breast cancer tumors including next-generation sequencing, circulating-free DNA in the plasma, and other technologies looking at the microenvironment. In my presentation, I just focused on next-generation sequencing and liquid biopsies. 

The most important area right now in terms of research is the profiling of metastatic tumors. In breast cancer, there are not as many mutations in cancer-related genes as we have seen in other tumor types, such as melanoma or others where the mutational load is not as big.

In The Cancer Genome Atlas study published in Nature a few years ago, they profiled 500 tumors and found that around 10% of all tumors had more than 6 mutations. Most tumors either had no mutations identified in the top-40 cancer-related genes or just had very few mutations. I don’t think we have the whole story about cancer drivers using genomic sequencing today. It is important information, but it remains a research tool to direct patients to clinical trials targeting those mutations.

These are all major challenges that we need to deal with. If we find a specific mutation, whether that mutation is a driver of the cancer or whether it is a passenger—meaning it is not driving the tumor phenotype—is still unclear. There are several examples where this technology may be useful in the future. We have found mutations in HER2 that may predict a response to neratinib (Nerlynx). For example, in one of the studies presented by Dr David Hyman at Memorial Sloan Kettering Cancer Center at the 2017 AACR Annual Meeting, findings demonstrated a promising approach to sequencing tumors.

However, in that study, researchers looked at breast cancer and other types of cancers. In mostly breast cancer with HER2 mutations without HER2 genome implication, they saw responses to neratinib. Not all mutations are the same, and not all mutations have the similar results in all tumor types as we may have thought. 

PI3K is another interesting gene where mutations have been associated with a better prognosis in breast cancer. The question is, “Can we use them to predict response to PI3K inhibitors or mTOR inhibitors?” To date, the data are inconclusive.

Another thought is the estrogen receptor (ER) mutations that may predict responses to different types of endocrine therapies, such as fulvestrant (Faslodex) compared with aromatase inhibitors. There are studies also looking at fulvestrant versus CDK 4/6 inhibitors, such as palbociclib (Ibrance), suggesting that they do not predict [responses with] CDK 4/6 inhibitors, but they may be predictive of response to some of the basic endocrine therapies. 

That research applies more to the liquid biopsies where we have been able to find mutations in circulating-free DNA in the plasma, which may be predictive but it is still an area of investigation. 

What are the current guidelines for genetic testing?

In patients with metastatic breast cancer, the biomarkers we always test for are ER, HER2, and perhaps BRCA. Now, since we are more interested in identifying BRCA mutations, it is standard of care—or at least recommended by national guidelines—to sequence the BRCA1/2 genes in patients with triple-negative breast cancer in which the ER, progesterone receptor, and HER2 tests are negative.

Next-generation sequencing, meaning sequencing an entire tumor, is not recommended as a standard of care yet. It is done whenever possible, and especially at the major academic institutions, with the goal being to direct those patients to clinical trials—single-institution trials, big institutions, and also the National Cancer Institute (NCI) MATCH trial, for example. This is where there are more than 20 arms depending on the mutations identified, so patients may be directed to those trials. 

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