From: Clinical Oncology
A randomized study of 1,300 patients has shown that omitting radiation is a reasonable option for women older than age 65 with early-stage, hormone receptor–positive breast cancer who undergo breast-conserving surgery and endocrine therapy. Omission of radiation in this patient group had no effect on survival and only a 2.8% increase in the risk for ipsilateral breast tumor recurrence (IBTR) over five years.
“Although radiation therapy reduces IBTR significantly, the absolute difference is very small,” said Ian Kunkler, FRCR, a professor of clinical oncology at the Edinburgh Cancer Research Center in Scotland. “An increasing proportion of patients that we see in the clinic, over 50%, have a relatively benign natural history. Radiotherapy might represent overtreatment.” Dr. Kunkler presented the study at the recent San Antonio Breast Cancer Symposium (SABCS; abstract S2-01).
The study included patients 65 years or older who had breast-conserving surgery for hormone receptor–positive, invasive breast cancer, and then were treated with adjuvant endocrine therapy. Eligibility criteria included tumor size up to 3 cm, excision margins of at least 1 mm on histologic assessment and no axillary node involvement on histologic assessment. Patients could not have previous in situ or invasive carcinoma of either breast, or current or previous malignancy within the past five years, except for non-melanomatous skin cancer or carcinoma in situ of the cervix. Patients received either whole breast irradiation (40-50 Gy in 15-25 fractions; n=658) or no irradiation (n=668). Baseline characteristics were well balanced between treatment groups.
Overall, the five-year actuarial local control rate was 4.1% in patients who did not receive radiation and 1.3% in patients who received radiation (P=0.002). There was no difference in overall survival. Factors such as tumor size, tumor grade, margin size and patient age (65-69 or >70) did not affect outcomes.
The investigators also conducted an unplanned analysis of local recurrence according to estrogen receptor (ER) status. High ER was defined as ER-positive, ER 7 or greater, fmol greater than 20, staining greater than 20 and triple-positive status. In the high-ER group, the addition of radiotherapy caused only a small reduction (2.4%) in IBTR (3.2% vs. 0.8%). In the low-ER group, 11.1% of patients in the nonirradiated group had local recurrence compared with 0% in the radiation group.
“Omission of postoperative radiation therapy in hormone-rich patients, based on the five-year rate of IBTR and overall survival, appears to be a reasonable option,” Dr. Kunkler said.
In 2005, the National Comprehensive Cancer Network amended its clinical practice guidelines to reflect that omitting radiation is a reasonable alternative in older patients with ER-positive, clinically node-negative T1 tumors who receive hormone therapy, however, clinicians have been slow to adopt this practice. The data presented at SABCS may swing the pendulum to less radiation.
“This study gives me a little more confidence that omitting radiation might be the safe thing to do in the right patient,” said Kent Osborne, MD, director of the Dan L. Duncan Cancer Center and the Lester and Sue Smith Breast Center at Baylor College of Medicine in Houston. “The absolute benefit [of radiation] is smaller, and I think that may well be enough to change practice. The small number of patients who do recur in the breast in the no-radiation group can be salvaged at that time by re-lumpectomy plus radiation or mastectomy.”
—Kate O’Rourke
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