FDA approves new pill for advanced breast cancer guided by blood test

by Ellyn Vohnoutka

edited by Gaby Clark, reviewed by Andrew Zinin

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The U.S. Food and Drug Administration (FDA) has approved a new daily pill for adults with advanced breast cancer whose tumors have found a way around their current treatment.

The drug, Etcamah (camizestrant), is taken alongside one of three existing cancer medicines called CDK4/6 inhibitors, a class of drugs that target specific enzymes in cancer cells.

It is meant for a specific group of patients: adults whose breast cancer grows in response to the hormone estrogen, does not carry a protein called HER2 and has spread beyond the breast or into nearby tissue.

Cancers like these are usually treated first with drugs that cut off the tumor's estrogen supply. But tumors adapt. One common escape route is a change in a gene called ESR1, which lets cancer cells keep growing even when estrogen is scarce.

Fewer than 5% of patients have that change when their cancer is first found to have spread, according to the FDA. Nearly 40% have it once the cancer starts growing again during estrogen-blocking therapy.

Etcamah is built to work against those resistant tumors.

Alongside the drug, the FDA authorized a blood test called Guardant360 CDx that finds the ESR1 change by picking up tiny fragments of tumor DNA floating in the bloodstream.

That is what makes this approval a first. The test can flag resistance before a scan shows the cancer growing, giving patients a chance to switch drugs earlier.

"This marks the first FDA approval of a cancer therapy guided by the detection of a resistance mutation in circulating tumor DNA before imaging tests show that the disease is progressing," Dr. Angelo de Claro, director of the FDA's Oncology Center of Excellence, said in a news release. "But additional evidence is needed to confirm clinical benefit."

In the trial behind the approval, patients who switched to Etcamah went a median of 16 months before their cancer worsened. Those who stayed on their original hormone therapy went 9.2 months. (Median means half went longer, half for less time.)

Doctors can now change course "at an earlier opportunity ahead of disease progression, rather than waiting until the cancer becomes harder to treat," Dr. Kevin Kalinsky said in a news release. He's a trial investigator and division director of medical oncology at Winship Cancer Institute of Emory University in Atlanta.

The FDA granted what is called accelerated approval, a faster path for drugs that treat serious illness.

It rests on early signs of benefit—here, extra months before the cancer grew—rather than proof that patients live longer.

The maker, AstraZeneca, must still run more studies to confirm the drug helps.

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