Tumor DNA test could assess efficacy of breast cancer treatment

March 19, 2013 | by Hiu Chung So

Just as diabetics have to check their blood sugar levels and HIV patients people have to monitor their viral loads, cancer patients and their doctors have to rely on regular, accurate testing to determine whether their therapies are working.

A separate blood test could help breast cancer patients and their doctors assess the effectiveness of treatment. Testing blood for DNA with tumor-specific alterations could help breast cancer patients and their doctors assess the effectiveness of treatment.

For women with advanced breast cancer, the current blood tests miss the mark about a third of the time, but scientists might have found a more powerful and accurate way to track disease progression. This could help oncologists evaluate, or switch, treatments for maximum effectiveness as early as possible. The results were published in the March 14 issue of The New England Journal of Medicine. In the study, 30 women with metastatic breast cancer underwent CT scans and provided blood samples. The blood was analyzed for circulating DNA with tumor-specific alterations; it was also assessed with two standard tests that look for tumor cells and CT 15-3, a breast cancer-specific antigen.

Among 19 of 30 women who had exhibited disease progression noticeable on CT scans, the tumor DNA test outperformed the other two, showing elevated levels for 17 women – compared to seven for tumor cell and nine for CT 15-3 tests.

Furthermore, 10 out of 19 women showed elevated tumor DNA levels months before the CT scans indicated progression, suggesting the test could help doctors determine earlier than is currently possible whether a regimen is working.

Although such research is promising, Yuan Yuan, M.D., Ph.D., assistant professor in the Department of Medical Oncology & Therapeutics Research, told WebMD that “this [test] is nowhere near being ready for clinical practice.”

Other experts agreed, citing the need for larger studies and for ways to make such a test more cost-effective and accessible.

But Yuan, who was not involved in this study, said that tumor DNA and other tests in development are indeed promising, possibly enabling better monitoring of patients in the future.

And that could very well mean a longer and better quality of life for women with metastatic breast cancer, who could be placed on treatments with the best clinical benefit and the fewest side effects.

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