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A test that measures a protein involved in tumor suppression may someday spare thousands of women from the pain and misery of unnecessary chemotherapy, researchers report.

In a study of more than 2,000 women with breast cancerbreast cancer, the test also identified those women for whom chemotherapy is most likely to help, says researcher A. Raymond Frackelton Jr., PhD, a staff scientist at Roger Williams Medical Center in Providence, R.I., and vice president of research at Catalyst Oncology, which is marketing the test.

The test, called OncoPlan, is already being used to predict disease aggressiveness. The new findings suggest the test "will also help to ensure that women receive the most beneficial therapies," he tells WebMD.

How Tumor Cells Thrive

The new research, presented here at a meeting of the American Association for Cancer Research, involved 2,380 women who were diagnosed with invasive breast cancer, 717 of whom received chemotherapy as part of their initial treatment.

All were given the new test, which measures the so-called p66 Shc protein in tumor cells which works to inhibit pathways involved in the development of aggressive cancer.

What this means, Frackelton says, is that tumor cells are better able to thrive and survive if p66 Shc levels are low.

Women With Low p66 Levels Benefit Most

In the study, the 60% of women classified as being at high risk of cancer recurrence due to low levels of p66 Shc were strongly protected by chemotherapy, with the drugs cutting in half their risk of relapsing and dying.

Conversely, among the 40% of women classified as being at low risk of recurrence due to high levels of p66 Shc, chemotherapy appeared to be a hazard.

All that is required for the test is a small slice of the tumor from a biopsy or surgical specimen. Len Lichtenfeld, MD, deputy chief medical officer of the American Cancer Society, says the test shows promise. However, "the predictive ability is not yet sufficient that oncologists would make a decision on whether or not to give chemotherapy based on the results," he says. "Further study is warranted."

Frackelton agrees, and says the company plans further testing to validate the results before marketing it for this use.

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SOURCES: Molecular Diagnostics in Cancer Therapeutic Development Meeting, Chicago, Sept. 12-15, 2006. A. Raymond Frackelton Jr., PhD, staff scientist, Roger Williams Medical Center, Providence, R.I.; and vice president of research, Catalyst Oncology Len Lichtenfeld, MD, deputy chief medical officer, American Cancer Society.

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