Two genes predict tumor’s progression to invasive breast cancer

A new genetic test may help determine whether a small tumor in the breast is likely to turn in to full-blown breast cancer, according to a study published Wednesday in the Journal of the National Cancer Institute.

The small tumor, called a ductal carcinoma in-situ, or DCIS, resides in the milk ducts and is generally considered pre-cancerous. But according to the study, DCIS lesions left untreated will eventually progress to breast cancer in about 50% of patients. The lesions, which tend to be small and only detectable via mammogram, have become increasingly common as mammography has become more widespread.

Given that about 50% of women with DCIS will not progress to breast cancer, researchers have begun focusing on determining which half is which.

In the new study, carried out by researchers at the University of Texas Southwestern in Dallas and Thomas Jefferson University in Philadelphia, researchers looked to see whether the absence of genes that have been previously identified as tumor suppressors might increase the likelihood that a DCIS lesion would progress to invasive breast cancer.

In particular, they focused on two genes: RB and PTEN, both of which have been previously associated with breast cancer progression. The researchers studied the tissue of 236 women who had had surgery to eliminate the tumor without removal of the whole breast, a technique called breast-conserving surgery.

The team found that only one of the tumor suppression genes -- RB -- was significantly associated with progression to invasive breast cancer, while PTEN showed a slight association. But when both genes were turned off, patients were five times more likely to have their DCIS tumor progress to full-blown invasive breast cancer: While only 10% of patients with both RB and PTEN turned on developed invasive breast cancer, 53% of those with both genes turned off developed cancer.

The researchers believe the finding could provide a method to personalize the care of patients with DCIS by applying more aggressive therapies to those who have the genes turned off.

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