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• Posted July 13, 2023

Targeted Treatment Shrinks Rare Brain Tumors in Small Study

A targeted treatment has had unprecedented success in shrinking a rare brain tumor, according to clinical trial results.

These tumors are papillary craniopharyngiomas (PCPs), and the drug combo is called vemurafenib/cobimetinib.

Each of 15 patients who received one or more cycles of targeted therapy responded to treatment, with an average 91% reduction in tumor size, Mass General Cancer Center researchers reported.

PCPs can cause substantial health problems. They are typically treated with surgery and radiation, but incomplete removal of the tumor and toxicity from radiation can leave patients with lifelong health challenges after treatment. This can include neuroendocrine dysfunction, as well as vision or memory loss.

"All patients who completed one or more cycles of therapy responded to treatment, which is the highest response rate to date of any medical therapy for brain tumors,"said study co-author Dr. Priscilla Brastianos, director of the cancer center's Central Nervous System Metastasis Center.

"These unprecedented results signal a paradigm shift for targeting brain tumors because they show that, with the right target and the right drugs, precision medicine can have a dramatic impact on brain tumors,"Brastianos added in a hospital news release.

This was the first multicenter treatment protocol in this rare tumor, according to Mass General Cancer Center, which led the study.

The findings were based on laboratory discoveries by researchers who studied the genetic drivers of PCP growth. They discovered that existing cancer medications can interfere with faulty genes in PCPs. This can halt their progression and drastically reduce their size, according to the study.

Previously, Brastianos and her colleagues showed that approximately 95% of PCPs have a type of mutation in the BRAF gene. This BRAF V600E mutation drives their cancerous activity. The mutation is also present in some forms of melanoma.

The U.S. Food and Drug Administration has recently approved therapies that inhibit BRAF and a related gene, MEK, for treating melanoma and some other cancers.

The investigators hypothesized that a BRAF/MEK inhibitor might also be effective for treating PCPs.

Researchers initially screened PCP patients across the country for BRAF V600E mutations. They enrolled 16 patients from nine centers, and 15 completed at least one 28-day cycle of the therapy.

Over four cycles, the mean reduction in tumor size was 91%, though it ranged from 68% to 99%.

Seven patients received no other treatment after discontinuing this targeted treatment. Six have not shown evidence of tumor progression at a follow-up of nearly two years. No patient's tumor progressed while on the medication. None has died.

Some patients stopped treatment, including one who experienced anaphylaxis and acute kidney injury. Six reported rashes. Yet many patients tolerated the drugs well and continued beyond the four cycles.

More research is needed to determine the optimal number of cycles, the researchers noted.

"This study demonstrated that national, biomarker-driven trials are feasible for patients with brain tumors,"Brastianos said. "Moving the needle on treating rare brain tumors truly requires a multidisciplinary and multi-institution effort, and we were able to highlight that through our research."

The research was supported by the U.S. National Cancer Institute and others. The findings were published in the New England Journal of Medicine.

More information

The U.S. National Library of Medicine has more on precision medicine.

SOURCE: Mass General Brigham, news release, July 12, 2023