Molecular test predicts risk of breast cancer recurrence
Source: (cancerfacts.com)
Friday, December 10, 2004
SAN ANTONIO – Dec. 10, 2004 – Researchers have moved a giant step closer to being able to determine which breast cancer patients are most likely to experience recurrence and which are least likely to, according to a new test presented today at the San Antonio Breast Cancer Symposium.
The gene test performed on a tissue sample taken from the tumor, can predict both the risk of breast cancer recurrence and may identify women who will benefit most from chemotherapy, thus potentially giving physicians the most precise treatment planning information yet.
Dr. Norman Wolmark, chair of the National Surgical Adjuvant Breast and Bowel Project (NSABP), which performed the research in collaboration with the National Cancer Institute and Genomic Health, Inc, which developed the assay, says the test could change standard practice for treating breast cancer.
"These data advance the state of the art in cancer care and call for a re-evaluation of treatment practice. By using the Oncotype DX assay, physicians can more effectively optimize a treatment plan and avoid under treating and over treating breast cancer patients," said Wolmark in a news release.
The advance is considered so significant, the New England Journal of Medicine published the results of the study online today ahead of the print edition next week.
Using samples from 447 patients and a collection of 250 genes in three independent preliminary studies, the researchers identified a panel of 16 cancer-related genes, the status of which best predicted recurrence.
Using a "recurrence score" based on the expression patterns of these genes in the tumor sample, they were able to more accurately predict the risk of recurrence than is now possible with current tests. Gene expression patterns refer to gene activity, or protein production. Active genes are producing proteins, and non-active genes are not.
The researchers then used tissue samples and medical records from 668 women enrolled in clinical trials of the cancer drug tamoxifen.
Using biopsy tissue and medical records they divided the women into low, intermediate, and high risk of recurrence groups based on the recurrence score. They found that 51 percent were in the low risk group, 22 percent were at intermediate risk, and 27 percent were at high risk group.
These risk group divisions correlated well with the actual rates of recurrence of breast cancer after 10 years as shown on the women's medical records. There was a significant difference in recurrence rates between women in the low and high risk groups. They found there was a 6.8 percent rate of recurrence at 10 years in the low-risk group, a 14.3 percent risk in the intermediate-risk group and a 30.5 percent chance of recurrence within 10 years of initial treatment in the high risk group.
The researchers also presented new results indicating that the same test can predict which women benefit most from chemotherapy. They were able to estimate that about half of the 50,000 U.S. women may be at low risk for recurrence and may not need to undergo chemotherapy with all its adverse side effects.
The significant advance of this study is that the genomic analysis is conducted using thin sections from standard diagnostic pathology specimens that are routinely available, making the test widely accessible. Previously, such genomic testing, as it is called, required frozen tissue samples, which are much more difficult and cumbersome to obtain for routine testing.
"The test has the potential to change medical practice by sparing thousands of women each year from the harmful short- and long-term side effects associated with chemotherapy," said Dr. JoAnne Zujewski, M.D., senior investigator in NCI's Cancer Therapy Evaluation Program.
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