Younger women were less likely to have estrogen-receptor-positive tumors (71 percent versus 80 percent in older women); more likely to have tumors which overexpress the protein HER2neu (52 percent versus 24 percent); more likely to have higher-grade tumors (56 percent versus 26 percent) and larger tumor size; more likely to have positive lymph nodes (38 percent versus 25 percent); and higher recurrence rates.
Women under 40 had even higher recurrence rates than women aged 40 to 45, although there appeared to be no differences in subgroups of women under the age of 40.
Compounds already in development may hold promise for treating younger women, the authors said, although the actual benefit for patients may be some years away.
"This doesn't mean anything for a young woman who has breast cancer [now], like the one that I saw yesterday afternoon," Brawley said. "It does mean that perhaps in five years, perhaps in 10, we will have more drugs like Herceptin. A study like this gives you the target."
Herceptin targets tumors which overexpress the HER2neu protein.
More information
The American Cancer Society has more on breast cancer.
