MONDAY, Dec. 17, 2007 (HealthDay News) -- Even if they're very small (1 centimeter or less), certain kinds of breast cancer tumors can still be aggressive and require maximum therapy, U.S. researchers say.
A team at the Mayo Clinic in Jacksonville, Fla., found that outcomes for women with HER2 positive (HER2+) and triple negative (HER2- and ER/PR-) tumors that have not spread to the lymph nodes may not depend on tumor size alone.
About 15 percent to 20 percent of breast cancers are HER2+, and about 10 percent to 15 percent are triple negative.
"This is a small study, and so we can't make treatment recommendations from it, but it appears that biology and not only size matters when it comes to selecting therapy for small, invasive tumors," lead researcher Dr. Surabhi Amar, a fellow in hematology/oncology, said in a prepared statement.
Amar noted there are no definitive treatment guidelines for breast cancer tumors less than one centimeter in size, because most studies include women with larger tumors or with breast cancer that's spread to the lymph nodes.
"We just don't have extensive data on tumors this small, so treatment becomes a matter of physician discretion," Amar said.
The study included 401 breast cancer patients: 350 with HER2 negative/ER/PR+ tumors; 27 with HER2+ tumors; and 24 with triple negative tumors. The women were followed for an average of about three years.
The researchers found that women with HER2+ and triple negative cancers were more likely (92 percent and 91 percent, respectively) to have grade 2 and 3 tumors than women with HER2 negative/ER/PR+ cancer (36 percent). Tumors are graded from 1 to 3. Higher grade tumors are more likely to grow faster and be difficult to treat.
The study also found that cancer recurrence was more common in women with HER2+ tumors (7.4 percent) and triple negative tumors (12.5 percent) than in women with HER2 negative/ER/PR+ tumors (1.3 percent).
The overall outcome for all the women with these small, lymph-node-negative tumors was excellent -- overall survival was 97.4 percent and disease-free survival 95.1 percent. One of the 24 patients with triple negative cancer died, none of the 24 women with HER2+ died, and one of the 219 women with HER2 negative/ER/PR+ cancer died.
The study findings suggest that women with small HER2+ and triple negative breast tumors should receive as much treatment as possible in order to prevent cancer relapse, Amar said.
But that doesn't appear to be happening. The study found that only 35 percent of women with triple negative cancers and 28 percent of those with HER2+ tumors received adjuvant chemotherapy (chemotherapy after surgery).
The study was to be presented Dec. 16 at the San Antonio Breast Cancer Symposium.
More information
The American Cancer Society has more about breast cancer.
