For breast cancer survivors, a common worry is a recurrence of their cancer. Currently, these patients are screened with regular mammograms, but there’s no way to tell who is more likely to have a recurrence and who is fully cleared of her cancer.
A new blood test – reported in Cancer Research, a journal of the American Association for Cancer Research – could potentially provide doctors and patients with the information they need to determine whose cancer has been eliminated and who needs more aggressive treatment.
The new blood-based assay is built on a panel of 10 breast cancer-specific genes. Blood collected from breast cancer patients is processed to isolate circulating tumor DNA. The test detects if any of the 10 genes are “hypermethylated.”
Hypermethylated genes indicate that the process used by some genes to keep cancers in check has been “silenced.” Thus, the presence of such genes suggests that the patient may have a disease recurrence and that further treatment is warranted.
The current guidelines for following a woman who has been treated for early stage – potentially curable – breast cancer is to examine her regularly, but no bloodwork or X-rays are recommended because they are unable to accurately identify any lingering cancer, said Mortimer, who wasn't involved in the study.
“Therefore, these women have to deal with the uncertainty of knowing whether they are in the ‘cured’ group or not,” she said. “Having an accurate blood test would allow us to know who has residual cancer and needs more aggressive therapy, and who does not.”
The assay was developed at Johns Hopkins University School of Medicine. The goal of the project was to develop a noninvasive assay test that could potentially detect recurrence in breast cancer patients sooner than traditional methods, and to have this test administered during scheduled follow-up care.
Using their assay, researchers were able to detect a drop in methylation levels as early as two weeks after it occurred – weeks before traditional imaging would be able to detect a recurrence. Development of the test relied on two strategies: sensitivity to ensure the methylated genes would be highly indicative of the tumor, plus specificity to ensure that the genes being tested are not hypermethylated in white blood cells or healthy tissue.
Through a genomewide search, the researchers selected genes specifically found to be methylated in blood and tumor tissues of cancer patients and chose genes that best differentiated between cancer and normal samples. The panel was tested in samples from patients who participated in clinical trials. The study found the blood test detected the presence of cancer DNA accurately.
Next, researchers analyzed blood samples from patients with metastatic breast cancer. These samples were collected before treatment and at different stages of treatment. Through these samples, researchers found a decrease in methylation levels in patients who responded to treatment, while no such decrease was observed in patients who did not respond to treatment or whose disease progressed. The test was given to 55 healthy women and 57 women whose breast cancer had spread.
"There is reason to be optimistic and study this further," Mortimer said in a HealthDay story. "
Mortimer, who was not involved in the research, said because only a small number of patients were studied, more study is warranted -- but that such a test is badly needed as other tests on the market are not accurate.
The test developers predict it will be available in the next five years.
Researchers acknowledge that the test requires further study, but they believe it may ultimately also prove useful in detecting recurring lung, colon and rectal tumors.
Learn more about City of Hope's breast cancer research and treatment.