Breast Cancer in Men Biologically Different Than Breast Cancer in Women

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Male Breast Cancer

Breast cancer in men is rare, but it does happen. Less than 1% of all breast cancers occur in men. For men, the lifetime risk of being diagnosed with breast cancer is about 1 in 1,000.

A study has found that the characteristics of male breast cancer associated with outcomes are different than the characteristics of female breast cancer that are associated with outcomes.

The study was presented on March 10, 2016 at the European Breast Cancer Conference. Read the abstract of “Pathologic prognostic factors of male breast cancer: results of the EORTC 10085/TBCRC/BIG/NABG International Male Breast Cancer Program.”

In the study, which was part of the International Male Breast Cancer Program, the researchers looked at 1,203 male breast cancer tumor samples from 1,483 men from 23 centers in nine countries.

The researchers looked at a number of cancer characteristics, including:

  • Grade: A low-grade cancer has cells that look a little bit different from normal cells and the cells are slow-growing. A high-grade cancer has cells that look very different from normal cells and the cells are growing quickly.
  • Subtype: Breast cancers can be estrogen-receptor-positive or estrogen-receptor-negative, progesterone-receptor-positive or progesterone-receptor-negative, and HER2-positive or HER2-negative. Cancers that are estrogen-receptor-negative, progesterone-receptor-negative, and HER2-negative are called triple-negative.

  • Breast cancer subtypes also include where in the breast the cancer starts. For example, ductal carcinoma in situ is a non-invasive cancer that starts in the milk ducts and hasn’t spread beyond them. Invasive lobular carcinoma starts in the milk lobules and spreads beyond them.
  • Tumor-infiltrating lymphocyte levels: Tumor-infiltrating lymphocytes are white blood cells that have left the bloodstream and moved into a cancer tumor. White blood cells are immune system cells made by your bone marrow to help your body fight infection.
  • Breast density: Male breasts are similar to female breasts, except male breasts don’t have many lobules, the milk producing gland, or ducts, the pipes that carry the milk from the lobules to the nipples. Still, both male and female breasts have fatty tissue and fibrous tissue, called stroma. Breasts with more fibrous tissue than fatty tissue are considered dense.

The researchers found that low tumor-infiltrating lymphocyte levels and high levels of fibrous tissue in male breasts were strongly associated with worse outcomes in male breast cancer. Cancer grade, which is strongly associated with outcomes in female breast cancer, wasn’t strongly associated with male breast cancer outcomes.

The researchers said that a possible reason for this lack of association between cancer grade and outcome in male breast cancer might be because male breast cancer tends to have different common subtypes than female breast cancer.

For example, lobular breast cancers are fairly common in women but rare in men. Triple-negative and HER2-positive breast cancers are more common in women than men. Most male breast cancers are estrogen-receptor-positive.

"However, this sub-typing of breast tumors does not seem to result in an optimal risk classification for male breast cancer patients," said Carolien van Deurzen, M.D., a pathologist specializing in breast cancer at the Erasmus Medical Center in The Netherlands who presented the research. "Additional tests that are well established in women, including gene-expression profiling, may result in the identification of more accurate prognostic and predictive markers. These could enable us to take better treatment choices, individualized for each patient, particularly in regard to the use of chemotherapy and new targeted agents."

The researchers hope to begin a clinical trial soon, using a new medicine that blocks the androgen receptor, a protein that is commonly present in male breast cancer.

"This will only be possible with a worldwide collaboration, but it is also important that male breast cancer patients should take part in general breast cancer trials, since trials for them alone are difficult to run due to the rarity of the disease," added Dr. van Deurzen. "In the past, male patients have been persistently excluded, with no scientific rationale for doing so. It is also essential to find independent sources of funding to study male breast cancer; once again, it is its rarity that makes this difficult."

Because breast cancer in men is so rare, it has been hard to study the best way to treat it, as Dr. van Deurzen said. Most male breast cancer treatments have been modeled on treatments for women. But as this study shows, that may not be the optimal way.

If you’re a man who’s been diagnosed with breast cancer and would like to participate in a clinical trial, visit the Breastcancer.org Clinical Trials pages to learn more about how these studies are done and how to search for a trial that is best for your unique situation.



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