Biomarker Found in Triple-Negative Breast Cancer

As the field of personalized medicine for cancer continues to grow, a new advance may one day add to a targeted approach in treating triple-negative breast cancer.

The unique biomarker reported by researchers may help doctors improve the prognosis of patients battling triple-negative breast cancer. The research was presented at an American Association for Cancer Research International Conference.

The disease's name refers to breast cancers that test negative for estrogen receptors, progesterone receptors, and human epidermal growth factor receptor 2 (HER2), all of which fuel most breast cancer growth.

According to the American Cancer Society (ACS), these breast cancers tend to occur more often in younger women and in African-American women. They tend to grow and spread faster than most other types of breast cancer.

Learning specifics of breast cancer

Receptors are proteins on cells that may attach to hormones that circulate in the blood. Normal breast cells and some breast cancer cells have receptors that attach to estrogen and progesterone. These two hormones often fuel the growth of breast cancer cells.

A biopsy can check to see if the cells have estrogen or progesterone receptors.

Cancer cells may contain neither, one, or both of these receptors. Breast cancers that contain estrogen receptors are called ER-positive (ER+) cancers, while those containing progesterone receptors are called PR-positive (PR+) cancers.

Women with hormone receptor-positive cancers tend to have a better prognosis and are much more likely to respond to hormone therapy than women with cancers without these receptors.

The ACS says that about one of five breast cancers have too much of a growth-promoting protein called HER2. The HER2 gene instructs the cells to make this protein. Tumors with increased levels of HER2 are referred to as HER2-positive.

Because triple-negative cancer cells do not have these receptors, neither hormone therapy nor drugs that target HER2 are effective against this cancer. The ACS says that chemotherapy can still be useful.

Although relatively uncommon, triple-negative breast cancer is notoriously difficult to treat because receptor targeted therapies have not worked.

"Triple-negative breast cancers currently lack therapeutic targets and are managed with conventional chemotherapy," says study author Agnieszka K. Witkiewicz, M.D., at Thomas Jefferson University Hospital.

Finding effective treatment an important goal

In search of new treatment targets, the study's research team analyzed expression levels of a particular protein called IGF-1R (insulinlike growth factor) among 97 patients diagnosed with triple-negative breast cancer. Seventy-three of the patients were Caucasian, and 24 were African-American.

Dr. Witkiewicz found that when it came to IGF-1R, more is better. High expression of the protein was tied to a lower risk for lymph node metastasis (spread of the cancer) and also had a link with smaller tumor size.

High expression levels were also linked to longer survival rates among patients younger than 55. Among the study patients, about one in four demonstrated IGF-1R over-expression.

Noting that IGF-IR has already proved to be a successful target in sarcoma treatment, Dr. Witkiewicz says it might ultimately prove to be a good target for triple-negative breast cancer, as well.

"For now, we know that it is there and we know it is a marker of better prognosis," says Dr. Witkiewicz. "The next step is to learn if triple-negative breast cancer patients benefit from targeting IGF-1R."

Always talk with your doctor to find out more information.