Two studies, from the United States and Italy, examined cases of women with small (1 centimeter or less in diameter) HER2-positive breast cancers that hadn't spread to the lymph nodes. The researchers found that the cancer is more than two times more likely to recur in HER2-positive women than in women with HER2-negative breast cancers.

The U.S. study, which looked at 965 women diagnosed between 1990 and 2002, also found that HER2-positive women had a more than fivefold higher risk of metastasis, in which the cancer spreads to other parts of the body, once the cancer returns than those with HER2-negative tumors.

The researchers estimate that only one in four breast cancers are HER2-positive. The new research, published in the Nov. 2 online edition of the Journal of Clinical Oncology, looked at those with small tumors.

Currently, the guidelines don't suggest that women with such small tumors receive treatment with the drug trastuzumab (Herceptin). However, the authors of the new studies recommend that the drug be considered for them.

"We expected the risk of recurrence and metastasis in HER2-positive node-negative patients with small tumors to be higher than in women with HER2-negative tumors, but we didn't expect the magnitude of this [increased] risk to be so high," Dr. Ana M. Gonzalez-Angulo, an associate professor in the department of breast medical oncology at the University of Texas M.D. Anderson Cancer Center and lead author of the U.S. study, said in a news release from the journal's publisher. "This elevated risk is unacceptable, and indicates that women with small HER2-positive node-negative breast tumors should be offered participation in clinical trials assessing anti-HER2 therapies, such as trastuzumab [Herceptin], or other adjuvant treatment."

More information

Learn more about breast cancer from the U.S. National Cancer Institute.