A new study confirms that women with breast cancer who are 35 years old or younger are more likely than older women to have their cancer come back after treatment.

The study also shows that the likelihood of recurrence in younger breast cancer patients is influenced by the type of treatment they received. The disease was less apt to recur in young women who had mastectomy plus radiation than in young women who had mastectomy alone or breast-conserving therapy.

The findings stem from a review of 652 women aged 35 or younger who were treated for breast cancer at the University of Texas M. D. Anderson Cancer Center over more than 30 years. In total, 197 of the women had breast-conserving therapy, 237 had mastectomy and 234 had mastectomy plus radiation.

For the group as a whole, the researchers found that the rate of relapse was 15.1 percent in women who had mastectomy plus radiation therapy, compared with 19.8 percent in women who had breast-conserving therapy and 24.1 percent for those who had mastectomy alone.

Women with early or "stage I" breast cancer had similar outcomes with breast-conserving therapy and mastectomy, but adding chemotherapy to either treatment was beneficial, the researchers found. "The data support consideration of chemotherapy for all patients (with stage I disease) until more definitive data are gathered regarding appropriate selection criteria," they wrote in the International Journal of Radiation Oncology, Biology, and Physics.

Women with "stage II" disease, they report, achieved the best control rates with mastectomy plus radiation therapy.

Recurrence of breast cancer after optimal treatment in young women "remains a significant problem," study leader Dr. Beth M. Beadle, of University of Texas M. D. Anderson Cancer Center in Houston, said in a statement issued by the American Society for Radiation Oncology (ASTRO).

Previous studies have shown that younger breast cancer patients consistently have poorer outcomes than patients who develop the disease later in life. While the reason for this is not clear, doctors suspect that breast cancer in younger patients is more aggressive.

"Our study hopefully will help radiation oncologists plan therapies for younger breast cancer patients, who have inferior outcomes compared to older patients, and generate new interest in prospective studies to evaluate the best treatment strategies for these young women," Beadle said.