Many patients living with metastatic breast cancer (mBS) now have a new treatment option.

In May 2019, the FDA approved a new targeted therapy, alpelisib (Piqray®). An oral medication intended to be used in combination with fulvestrant (Faslodex®), Piqray® is indicated for post-menopausal women and men with HR-positive, HER2-negative metastatic breast cancer with a PIK3CA mutation whose disease has progressed while on or after completing endocrine therapy.

About 40 percent of patients with HR-positive, HER2-negative metastatic breast cancer are projected to have the PIK3CA mutation, which is confirmed through molecular testing of a specimen of either primary or metastatic breast tumor tissue.

“This is another exciting breakthrough in personalized medicine,” says Noah Brown, M.D., Director of MLabs’ Molecular Oncology and Genetics Laboratory, “and the latest evidence of the crucial role molecular pathology is playing in emerging cancer solutions.”

All assays are not created equal

Along with approving Piqray®, the FDA also designated a commercially available assay, Therascreen® PIK3CA RGQ PCR, as a “companion diagnostic test” to identify the PIK3CA mutation.

“The field of precision oncology is changing so rapidly that patients – and even some providers – may not be familiar with the molecular testing required for the latest targeted therapies,” Brown says. “The recent approval of alpelisib represents a significant development in the treatment of metastatic breast cancer. More than 150,000 patients in the U.S. are living with metastatic breast cancer and approximately 70 percent of cancers are HR positive and HER2 negative. Of these, about 40 percent harbor a PIK3CA mutation and could benefit from this treatment.”

MLabs offers its own molecular test to identify PIK3CA: MLabs’ NGS (next-generation sequencing) Solid Tumor Panel. Comparing the two reveals major differences.

“The Therascreen assay detects the 11 most common PIK3CA mutations,” explains Brown. “However, there are many more less common, yet well-described activating PIK3CA mutations that can be detected using a broader screening platform like the next generation sequencing platforms that are quickly replacing single-gene testing for many applications.”

MLabs’ NGS Solid Tumor Panel interrogates 34 other genes for substitution and insertion/deletion mutations, as well as 19 genes for copy number changes and 21 genes for oncogenic gene fusions. This panel was specifically designed to cover both standard of care and emerging molecular alterations relevant for targeted therapies.   

“This more comprehensive form of molecular profiling is quickly emerging as the preferred approach,” continues Brown. “It enables oncologists and patients to pursue both well-established targeted therapies and emerging therapies with clinical evidence of efficacy and/or those being explored in clinical trials. In short, this approach enables molecular testing results to keep up with the quickly evolving field of precision medicine.”

Less tissue, more results

MLabs not only delivers a more complete diagnostic picture than most commercial reference labs; it does so with greater reliability, from a much smaller specimen.

“Most targeted therapies – as is true for alpelisib – are relevant for patients with metastatic cancer. That makes the ability to perform molecular testing on small biopsies and aspirates critical for patient care,” explains Brown. “Our Solid Tumor NGS Panel was specifically designed for the smallest of tissue specimens – less than one square millimeter of tissue. As a result, our QNS/failure rate is less than three percent.”

By comparison, other leading laboratories require specimens of 25 square millimeters or larger and can have QNS/failure rates of 20 percent or greater.

“The ability to give patients and their oncologists results when specimen size is limited is extremely important for patient care,” adds Brown. “It enables many more patients to receive targeted therapies with greater efficacy and lower side effect profiles than other treatment options.”

(See a side-by-side specimen comparison here: http://mlabs.umich.edu/molecular-diagnostics/less-tissue-more-results/

MLabs is currently accepting specimens for PIK3CA testing. In addition to the NGS Solid Tumor Panel, MLabs offers a single gene assay for PIK3CA with broad coverage of PIK3CA mutations.

More about the NGS Solid Tumor Panel, including a complete list of genes assessed for mutations, amplifications and fusions, as well as test requisition information, can be found here: https://www.pathology.med.umich.edu/handbook/#/details/5281