CHICAGO—Older women with early-stage breast cancer undergoing lumpectomy may not need adjuvant radiation treatment, according to a large intergroup trial reported at the ASCO Annual Meeting.
In women aged 70 or older with early-stage disease, postlumpectomy radiation therapy did not appear to affect survival, breast-cancer-specific survival, distant metastases, or mastectomy rates, Kevin S. Hughes, MD, Co-Director of the Avon Comprehensive Breast Evaluation Center and Associate Professor in the Department of Surgery at Massachusetts General Hospital, said at a telebriefing held in advance of the meeting.
“We found that radiotherapy did have some benefit in terms of in-breast recurrence, but those benefits were relatively small.
“You can get about a 6% reduction in in-breast recurrence with the addition of radiation, but it has no impact on the ultimate ability to preserve the breast, no impact on distant metastases, no impact on breast-cancer-specific morality, and no impact on overall survival.”
The study is a follow-up to the Cancer and Leukemia Group B (CALGB) 9343 trial, whose earlier results showed that after a median follow-up of 7.9 years, tamoxifen alone is an effective alternative to tamoxifen plus radiation in women age 70 and older with Stage I estrogen receptor-positive breast cancer (NEJM 2004; 351: 971-77).
The new analysis, which includes follow-up data after 10.5 years, confirms and extends the results, Dr. Hughes said.
The study involved 636 patients who were 70 or older with Stage I, node-negative, estrogen-receptor-positive breast cancer, all of whom had breast-conserving surgery.
Patients were randomized in a one-to-one fashion to tamoxifen or tamoxifen plus radiation therapy.
The primary endpoints were time to locoregional recurrence, and rates of mastectomy, distant metastases, breast-cancer-specific mortality, and all-cause mortality.
No Major Benefit to Radiation
After a median follow-up of 10.5 years, there was a small benefit for radiation therapy only in time to local recurrence, Dr. Hughes reported.
Patients randomized to tamoxifen alone had a freedom from in-breast recurrence rate of 8% vs 2% for those who received radiation therapy in addition to tamoxifen. In absolute terms, 26 of 319 patients in the tamoxifen-alone group had in-breast recurrences compared with six of 317 women in the radiation arm.
“Essentially, we would have to irradiate 319 women to prevent 20 in-breast recurrences, which is a fairly small benefit,” Dr. Hughes said.
Otherwise, there was no significant difference in the endpoints between the two groups.
The probability of being free from mastectomy at 10 years was 96% for the tamoxifen-only group and 98% for the tamoxifen plus radiation group.
The 10-year distant-metastases rate was 5% in both groups.
The 10-year breast-cancer-specific survival was also similar between the two groups: 98% for tamoxifen only and 96% for tamoxifen plus radiation. The overall survival rate was 67% in both groups.
“In terms of survival, a large number of women did die [but that is] because we're looking at an older-age population. Only 12 women in the radiation group died from breast cancer and only eight in the tamoxifen group, so the majority died of other causes.
“Death from breast cancer is a rare event for older women with these early-stage, very small, clinically node-negative breast cancers,” Dr. Hughes said.
Avoiding Radiation Feasible
“The question now becomes whether tamoxifen is enough treatment for women age 70 and older with these small cancers. Certainly, this needs to be discussed with patients, but I feel that avoiding radiation therapy in this group is very feasible.”
ASCO 2009-2010 President Douglas W. Blayney, MD, said the findings were “certainly practice affirming and may be potentially practice changing.”
“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,” he continued. “I think this study gives us some level of comfort as physicians in supporting that decision on patients' behalf and might even change the recommendations we make to patients.”
And George W. Sledge Jr., MD, ASCO 2010-2011 President, said the study clearly establishes tamoxifen alone as a reasonable alternative to tamoxifen plus radiation in these older patients.
“Even though there was a slightly higher rate of breast recurrences with tamoxifen alone, these were successfully treated with surgery. Overall survival and breast-cancer survival are all essentially identical,” he said.
Dr. Hughes said that radiation alone may be even more effective than when the trial began.
That's because the standard for clear surgical margins used to be “no ink on tumor,” compared with 1 to 2 mm today, he explained. “Today, with larger margins, I think that this decrease in recurrence would be even greater.”