New research shows how breast cancer tumors work ahead to get access to bones. We may already have the medications that can prevent that from happening — and doctors are encouraged.

Breast cancer that stays in the breast doesn’t kill. Breast cancer becomes a potential killer when it spreads outside the breast.

This spread to other sites occurs when cancer cells break off from the breast tumor. The cells then enter the lymph nodes or bloodstream, where they can reach any part of the body.

In a potentially groundbreaking development, researchers from the University of Sheffield and University of Copenhagen have discovered an enzyme that damages bones before the arrival of breast cancer cells.

The enzyme, LysYl Oxidase (LOX), is released from the primary tumor. LOX creates holes in bones. It acts as a primer, making it easier for cancer cells to take hold.

Once cancer reaches bone, it’s called metastatic breast cancer, or stage 4 breast cancer. And it’s a lot harder to treat.

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The discovery could be the key to preventing breast cancer from spreading to bone. If doctors can identify LOX in breast cancer patients, they may be able to block the enzyme’s action. That could prevent bone damage and make it harder for tumor cells to grow in bones.

The research also showed that treatment with an existing drug class can prevent those bone changes in mice. The drug, bisphosphonate, is primarily used to stop bone loss due to osteoporosis.

If the medication can help protect the bones of breast cancer patients, it could result in fewer cases of bone metastases.

Study authors say the next step is to determine how LOX interacts with bone cells. That will help in the development of new drugs to stop bone lesions from forming.

The study was co-led by Alison Gartland, Ph.D., and Janine T. Erler, Ph.D. Details were published in the journal Nature.

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What does this research mean for today’s breast cancer patients?

Erler told Healthline that bisphophonates are already being used in breast cancer patients; so using them in the adjuvant setting should be fairly straightforward.

LOX inhibitors are another matter.

“Using LOX levels to identify patients needs further development,” said Erler. “LOX inhibitors are not yet in the clinic, so those aspects will take some years.”

Dr. Michaela L. Tsai is a breast oncologist with Minnesota Oncology at Abbott Northwestern Hospital in Minneapolis. She said other studies over the years have suggested that bisphosphonate treatment can reduce the risk of cancer spreading to bones. This is especially true in postmenopausal women. But other studies have not shown the same success.

“Perhaps the discovery of LOX may help oncologists better determine who will benefit from bisphosphonate treatment,” said Tsai. “This will need additional study and testing on clinical trials. Currently, I do treat women at risk for metastatic breast cancer who have osteopenia or osteoporosis with a bisphosphonate.”

Breast cancer that spreads to the bone is treatable but not curable, said Tsai.

The American Cancer Society estimates that in the United States, there will be 234,190 new cases of invasive breast cancer in 2015. About 40,290 women and 440 men will die from it.

Most deaths from cancer are due to metastases. Bone metastasis accounts for about 85 percent of metastatic breast cancer patients. The five-year survival rate for stage 4 breast cancer is 22 percent.

According to the Metastatic Breast Cancer Network, about 155,000 people in the United States are living with metastatic breast cancer.

Tsai told Healthline some patients can live for years with bone metastasis, but treatment is different for different types of breast cancer. So is quality of life.

“Some women [or men] have bone metastases and are asymptomatic. Others can have severe pain. If so, pain control is our top priority,” said Tsai.

“Sometimes cancer spread to the bone leads to a weakening of the bone and a fracture or broken bone. This can pose limits on mobility and function. Once mobility and functionality are addressed and pain is under control, many people do have a very good, if not normal, quality of life,” she said.

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According to Tsai, this particular study won’t impact people already living with bone metastases. But it does offer hope for the future. Someday, it may help identify women at higher risk of bone metastases who may benefit from bisphosphonate treatment as a preventative measure.

Dennis Citrin, M.D., Ph.D., medical oncologist at Cancer Treatment Centers of America at Midwestern Regional Medical Center, is also encouraged by the study.

“What is so unique and exciting about the study published in Nature is the discovery of the LOX enzyme,” he said. “This enzyme produces holes in the bone and when it is blocked in early stage breast cancer, we have a better chance of preventing the spread of disease.”

“This development will hopefully lead to more specific and effective drugs to prevent and treat cancer induced bone destruction,” he added.

Citrin also notes that early-stage breast cancer is highly curable, which is why early diagnosis is so important.

“Women with early-stage breast cancer can be very optimistic about their quality of life and remission as long as they follow the advice of their healthcare team,” he said. “Of course, bone metastases can develop. The disease can recur at many different sites, but the best way to avoid recurrence is by completing the full treatment plan recommended for the patient.”