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CHICAGO -- Postlumpectomy radiation therapy had minimal impact on outcomes in older patients with early-stage breast cancer, data from a larger intergroup trial showed.

The addition of radiation therapy to tamoxifen led to an absolute decline in local recurrence of 6% to 7% versus tamoxifen alone. Adjuvant radiation had no effect on the ultimate breast preservation, distant metastases, breast cancer mortality, or all-cause mortality.

"At 10 years of follow-up, 95% of the patients had developed no distant metastases, essentially a 95% cure rate," Kevin S. Hughes, MD, of Massachusetts General Hospital in Boston, said at a press briefing in advance of his presentation at the American Society of Clinical Oncology meeting.

"In terms of survival, a large number of women did die because we're looking at an older-age population," he continued. "Almost all patients died of something other than cancer. There were eight breast cancer deaths in the tamoxifen group and 12 in the group that received tamoxifen plus radiation therapy.

"The main problem for these women is death from other causes. Death from breast cancer is a rare event for older women with these early-stage, very small, clinically node-negative breast cancers."

The findings confirm and extend results investigators in the intergroup trial reported after eight years of follow-up (N Engl J Med 2004; 351: 971-77). Then, as in the current study, only a small reduction in recurrence rate distinguished the two groups.

The findings came from the Cancer and Leukemia Group B (CALGB) 9343 trial, designed to determine whether adjuvant radiation plus tamoxifen would improve outcomes relative to tamoxifen alone in women ages 70 and older with stage I, receptor-positive breast cancer.

The study initially involved 636 patients, all of whom had breast-conserving surgery. The primary endpoints were time to locoregional recurrence, mastectomy for recurrence, distant metastasis, and breast cancer-specific and overall survival.

After a median follow-up of 10.5 years, the addition of radiation therapy to tamoxifen significantly prolonged the time to first recurrence (P=0.015) as a result of better local control with tamoxifen plus radiation therapy. Patients randomized to tamoxifen alone had a local recurrence rate of 9% and ipsilateral recurrence rate of 8% compared with 2% for both outcomes among patients who received radiation therapy in addition to tamoxifen (P<0.001). Six patients in the radiation therapy group had in-breast recurrences compared with 26 in the tamoxifen arm.

The 10-year probability of freedom from mastectomy was 96% with tamoxifen alone and 98% with tamoxifen plus radiation therapy. Breast cancer-specific and overall survival at 10 years were 98% and 63%, respectively for the tamoxifen arm versus 96% and 61% for the radiation therapy group.

"The question now becomes whether tamoxifen is enough treatment for women ages 70 and older with these small cancers," said Hughes. "Certainly, this needs to be discussed with patients, but I feel that avoiding radiation therapy in this group is very feasible."

When the trial began, the standard for clear surgical margins was "no ink on tumor," essentially a one-cell clear margin, he added. The current standard is 1 to 2 mm.

"Today, with larger margins, I think that this decrease in recurrence would be even greater," said Hughes.

The findings are practice-affirming at the very least and possibly practice-changing, said ASCO president Douglas Blayney, MD.

"When my colleagues discuss the merits of breast irradiation with older women, and they understand the small benefit, many of them elect to defer radiation therapy, which has been the practice for about 20 years," said Blayney, of the University of Michigan.

"I think this study gives us some level of comfort as physicians in supporting that decision on patients' behalf and might even change recommendations we make to patients."

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