Highlights From the San Antonio Breast Cancer Symposium 2019

I always come back from the San Antonio Breast Cancer Symposium overflowing with information and insights about the latest developments in breast cancer research.

This year, we learned about fascinating research in areas such as matching treatments better to individuals based on the molecular characteristics of their cancer and finding more ways to bring immunotherapy into breast cancer treatment.

As always, much of the research presented at San Antonio is future-oriented–it’s not going to change treatment options tomorrow. But this year there were even some findings that have pretty exciting near-term impact.

In this post, I’m going to share my top three “take-home” highlights from the 2019 symposium, starting with what I think is the biggest story this year–a new treatment for HER2-positive metastatic breast cancer (MBC).

Novel Treatment for HER2-Positive Metastatic Breast Cancer

Metastases to the brain are very common in HER2-positive MBC and may affect as much as half of this patient group. Unfortunately, cancer therapies often don’t work against  brain mets because the blood-brain barrier–which is meant to protect the brain–prevents large-molecule drugs (which most cancer drugs are) from entering the brain. As a result, patients with brain mets have typically been excluded from clinical trials.

So, it was quite exciting to hear about the findings of the HER2CLIMB clinical trial, the first Phase 3 clinical trial to include patients with progressing brain mets.

The trial tested an investigational therapy called tucatinib. Tucatinib is a tyrosine kinase inhibitor, a type of targeted therapy. It’s given as an oral medication.

Individuals in the trial had already received several types of treatment for their MBC, and their cancer was progressing. In this trial they were randomized to receive either tucatinib in combination with traztuzumab (Herceptin) and capecitabine (Xeloda) or a placebo together with Herceptin and Xeloda.

The results were striking. After two years, the overall survival rate was 45% for patients receiving tucatinib compared to 27% in the no-tucatinib group. And patients with brain mets–about half of the patients in the trial–experienced a 52% reduction in progression or death.

Tolerability was considered to be pretty good too, with few patients having to discontinue the treatment due to adverse side effects.

The trial findings were published in the New England Journal of Medicine. It’s expected that researchers will move quickly to seek FDA approval for this treatment regimen, which could become a new standard of care for patients in this population with or without brain mets.

Liquid Biopsy Helps in Treatment Choices for MBC

A liquid biopsy is a blood test that’s designed to evaluate the presence of tumor cells or bits of tumor DNA circulating in a patient’s bloodstream.

Liquid biopsies have been mostly experimental so far, but we learned that is changing as the tests improve.

The PlasmaMATCH trial is a large clinical trial that enrolled about 800 patients with MBC.  Its purpose was to find out whether testing for circulating tumor DNA is a reliable method of identifying mutations that occur as tumors evolve and may be drivers in a patient’s cancer. This is useful information if effective treatments targeting those mutations are available.

The trial found that testing for circulating tumor DNA is a simple, efficient and relatively fast method of tumor genotyping. It also found that patients whose tumor cells had certain specific mutations (e.g. HER2 mutations, AKT1 mutations) could be matched with corresponding targeted therapies.

Immunotherapy in Early Stage Triple Negative Breast Cancer

Earlier this year, the US FDA granted its first approval of an immunotherapy drug for the treatment of metastatic triple negative breast cancer. The drug approved was a “checkpoint inhibitor”–a type of drug that “releases the brakes” on the immune system.

Could immunotherapy with a checkpoint inhibitor be beneficial for early stage triple negative breast cancer?  The KEYNOTE-522 clinical trial was designed to help answer that question. This was the first Phase 3 trial combining immunotherapy and chemotherapy prior to surgery for early stage TNBC.

Presenters at the Symposium gave an updated analysis of study findings that had been first reported in September. The study found that all subgroups of patients receiving this treatment regimen before surgery benefited significantly.

After surgery, patients continued with the immunotherapy drug, pembroblizub (Keytruda), or a placebo for an additional 27 weeks, depending on how they had been randomized in the study. Further follow-up will be needed to find out whether this treatment strategy reduces recurrence rates and improves overall survival for this patient group.

For More Information

Here are some resources for more information on the findings presented this year at San Antonio:

Related Posts
San Antonio Breast Cancer Symposium 2015: “These Data Belong to Our Patients”
San Antonio Breast Cancer Symposium 2014: Where Is Research Headed?
San Antonio Breast Cancer Symposium 2013: What Did We Learn?

Photo by Lisa DeFerrari

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