Cancer Treatment Based on Test of Tumor Cells

Cancer researchers have developed a sensitive blood test to measure HER-2 gene expression in circulating tumor cells. Results obtained using this test revealed that the state of gene expression in the circulating cells reflected the state of the primary tumor, suggesting that the test may provide information that will permit physicians to prescribe individualized chemotherapy.

Investigators at the University of Texas Southwestern Medical Center (Dallas, USA; www.utsouthwestern.edu) developed a method for evaluating the HER-2 gene status of circulating tumor cells obtained from patients with reoccurring breast cancer by using fluorescence in situ hybridization. The test is able to detect one circulating tumor cell in 10 million white blood cells.

Results published in the June 11, 2004, online edition of the Proceedings of the [U.S.] National Academy of Sciences showed that the HER-2 status of the primary tumor and corresponding circulating tumor cells in 31 patients showed 97% agreement, with no false positives. Nine of 24 breast cancer patients whose primary tumor was HER-2-negative each acquired HER-2 gene amplification in their circulating tumor cells during cancer progression. This finding prompted their physician to begin treatment with Herceptin (an antibody to HER-2). Four of the nine patients were then treated with Herceptin-containing therapy. One had a complete response and two had a partial response.

"Cancer is a moving target, and the oncologist has to know which bullet to put in his gun,” said senior author Dr. Jonathan Uhr, professor of microbiology and internal medicine at the University of Texas Southwestern Medical Center. "Obtaining repeated blood samples is a safe and routine procedure, and this test can help the oncologist determine whether a new genetic change has become dominant and calls for a specific treatment for that change.”



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University of Texas Southwestern Medical Center