A clinical trial shows that a genomic test from diagnostics company Exact Sciences can help more women with early-stage breast cancer avoid chemotherapy.
The test, Oncotype DX, had already demonstrated its ability to predict whether chemotherapy would benefit women with breast cancer that has not spread to lymph nodes, known as node-negative breast cancer.
The new results demonstrate the test’s ability in evaluating postmenopausal women with node-positive breast cancer, a more aggressive form of the disease.
“These results mean that going forward tens of thousands of women this coming year can be spared chemotherapy,” Dr. Steven Shak, chief medical officer at Exact Sciences, said in a phone interview.
Based in Madison, Wisconsin, Exact Sciences is perhaps best known for developing Cologuard, a noninvasive screening test for colorectal cancer. But the company has been developing tests for other cancers as well.
Work on Oncotype DX began in 2000 at Genomic Health, said Shak, a co-founder of Genomic Health. He joined Exact Sciences in 2019 after it bought Genomic Health. Oncotype DX first became available in 2004 and versions can be used in screening for breast, colon and prostate cancers.
There are two versions for breast cancer. One predicts the likelihood of recurrence in a pre-invasive form of breast cancer called ductal carcinoma in situ, or DCIS. The second is used for patients with a form of the disease known as hormone receptor-positive HER2-negative breast cancer, which afflicts 73% of the roughly 270,000 women diagnosed each year with breast cancer. Most receive chemotherapy, which can have severe side effects.
“That one-size-fits-all approach was overused in breast cancer,” he said.
The genomic test assigns what is called a breast recurrence score between zero and 100 to determine whether chemotherapy will bring any benefit. Higher scores indicate a greater potential benefit.
An earlier trial, known as TAILORx, found in 2018 that the test could identify roughly 80% of the women with node-negative breast cancer who would not benefit from chemotherapy.
The latest trial, known as RxPONDER, showed results for women with node-positive breast cancer, who represent about 25% of the patients with hormone receptor-positive HER2-negative breast cancer. According to the company, Oncotype DX identified a majority of women who gained no benefit from chemotherapy. The group was made up of postmenopausal women with Oncotype DX scores between zero and 25. Premenopausal were found to benefit from chemotherapy regardless of their scores.
“These results are practice changing and demonstrate that the great majority of postmenopausal women can be spared unnecessary chemotherapy and receive only hormone therapy. This should bring more clarity to physicians and some relief for patients,” study lead author Dr. Kevin Kalinsky, said in a statement. He is a long-time investigator with the SWOG Cancer Research Network and director of the Glenn Family Breast Center at the Winship Cancer Institute of Emory University.
SWOG plans to submit the results to a peer-reviewed journal. They were first presented in December at the annual San Antonio Breast Cancer Symposium.
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