An enzyme found in some breast tissue is a strong indicator that a woman develop the cancer later in life.
Before now, if women at a high risk for breast cancer had a lump biopsied and the results were negative, there was no way for doctors to know if they might develop cancer decades from now.
The findings of a new Mayo Clinic study may change how doctors predict who will develop the cancer and how they look for it.
The study examined the non-cancerous biopsies of women who were at high risk for breast cancer. They had a proliferation of atypical cells, or atypia, and that made them four times as likely to develop the disease than women who were on long-term hormone replacement therapy. That's another known risk factor for breast cancer.
Every year, more than 50,000 women receive biopsy results with atypia.
But oncologist Dr. Lynn Hartmann said no one could say why some of those women later developed breast cancer and other did not. So researchers looked at what the tissue samples had in common: the enzyme COX-2.
"We've asked, can one marker, in this case COX-2, can it differentiate those women who have atypia who are going to go forward and develop breast cancer versus those who are less likely to do so?" Hartmann said. "And the answer is yes."
The enzyme COX-2 is often present in stressed and atypical cells. It causes pain and inflammation. It suppresses the immune system locally and tells the surrounding tissue to grow more aggressively. Hartmann said that gives atypical cells a growth advantage.
The study found that the amount of COX-2 in the biopsy tissue directly correlates to whether a woman develops breast cancer.
"If they had no COX-2 present in the sample at 15 years after the biopsy, 13 percent had developed breast cancer," Hartmann said. "If there was strong COX-2 twice that many had developed breast cancer."
After 20 years, 31 percent of those women had breast cancer.
Hartmann said all of her research is about predicting the real risks for breast cancer in women. Before now, doctors did not consider the presence of COX-2 as a sign a benign tumor was more likely to turn malignant. Hartmann thinks these findings could revise the way doctors evaluate a woman's cancer risk.
"Could we take a core needle biopsy from asymptomatic normal women when they are starting breast cancer screenings and look for these same feature. And see, can this work?" Hartmann said. "Could it really feed into a much smarter surveillance strategy?"
This finding could have an impact beyond detecting risk factors. Drugs already exist to inhibit COX-2.
Aspirin is a general COX inhibitor, and the drugs Vioxx and Celebrex target COX-2. Hartmann says if other studies validate her findings, inhibitors could be used as a breast cancer preventative for women at high risk.