A blood test that can identify a variety of mutations in advanced breast cancer can reliably match women to effective treatments, according to early results of a major clinical trial published in The Lancet Oncology.

The plasmaMatch trial, which is largely funded by Stand Up To Cancer, is investigating whether a simple blood test known as liquid biopsies can benefit patients with breast cancer by tracking their disease as it evolves. The information gathered from this blood test can help direct care givers toward the most effective treatments. 

Investigators analyzed blood samples from more than 1000 women with breast cancer that had recurred after treatment or spread to other parts of the body to determine whether the blood test could improve treatment. The researchers specifically wanted to see whether the test could improve treatment for patients whose breast cancer is caused by any of a variety of rarer mutations, rather than better-known defects, such as BRCAmutations.  

Investigators examined 3 targetable defects—human epidermal growth factor receptor 2 (HER2), v-akt murine thymoma viral oncogene homolog 1 (AKT1), and estrogen receptor 1 (ESR1)—all of which are known to contribute to breast cancer. Of the 1000 women, a total of 142 with 1 of these 3 mutations were given experimental drugs meant to target against the specific characteristics of their cancer. 

Women with the ESR1 mutations were treated with fulvestrant, whereas patients with the HER2 mutation either received neratinib on its own or in conjunction with fulvestrant. Patients with the AKT1 mutation were spilt into 2 groups based on whether their cancer was estrogen receptor positive. Patients with the AKT1 mutation were either treated with capivasertib plus fulvestrant or with capivasertib on its own. 

Five of the 20 women with rare HER2 mutations matched to neratinib saw a beneficial response, meaning cancer growth slowed or stopped, or the size of tumors shrunk. Four of 18 patients with AKT1 mutations responded to capivasertib; however, the ESR1 mutation treatment was not found to be effective.  

"Our Stand Up To Cancer initiative allows us to quickly transform any promising discoveries made in the lab into new tests and treatments for people with cancer,” Michelle Mitchell, OBE, chief executive of Cancer Research UK, said in the press release. “So, it's absolutely fantastic that we are looking at the possibility of using a simple blood test to quickly match the best treatments for women with advanced breast cancer. It's results like these that will help us see 3 in 4 people survive their cancer by 2034."

Reference:
Major trial uses blood test to match women with breast cancer to precision treatments [News Release] September 10, 2020. London, UK. https://www.eurekalert.org/pub_releases/2020-09/iocr-mtu091020.php. Accessed September 15, 2020.