By Steven Reinberg
NEW YORK (Reuters Health) – Gene expression patterns seen on DNA microarrays can identify breast cancers that are likely to metastasize, according to a report in Nature for January 31.
"We looked at tumors of 117, lymph node-negative, female breast cancer patients, younger than 55 years of age, and evaluated the gene activity pattern of the tumors," lead author Dr. Laura J. van't Veer, from The Netherlands Cancer Institute, Amsterdam, told Reuters Health.
Dr. van't Veer and colleagues were able to differentiate the gene expression signature of tumors that developed a distant metastasis, and had a poor prognosis, from those of women who remained disease-free for at least 5 years.
The research team was able reduce the number of genes examined from 5,000 to 70 to determine prognosis. "This gene activity pattern of 70 of the genes we looked at is able to foretell whether the outcome of disease is likely to be poor or good," Dr. van't Veer said.
Using the 70-gene classifier in a validation group of 19 lymph node-negative breast cancer patients, only 2 of the outcomes were incorrectly classified, the researchers note.
Based on gene expression patterns, only about 20% to 30% of women are at risk for metastatic disease, yet most are treated with chemotherapy or hormonal therapy in addition to surgery, Dr. van't Veer said. "Therefore we are overtreating 70% to 80% of breast cancer patients," she commented.
These findings will have to be confirmed in a group of unselected breast cancer patients, which the investigators are doing right now, she said. "Also the test has to be made into a routine diagnostic procedure, which we are also developing. We hope to see this test in clinical practice within 2 years," Dr. van't Veer said.