Long-term follow-up of Cancer and Leukemia Group B (CALGB) 9343 “confirms and extends the earlier report that in women age ≥ 70 years with clinical stage I, [estrogen receptor (ER)]-positive breast cancer treated with lumpectomy followed by tamoxifen, irradiation adds no significant benefit in terms of survival, time to distant metastasis, or ultimate breast preservation,” researchers reported in the Journal of Clinical Oncology. Radiation therapy did, however, provide a small decrease in ipsilateral breast cancer recurrence, the investigators added.
CALGB 9343 randomly assigned women at least 70 years old with clinical stage I, ER-positive breast cancer treated with lumpectomy, to receive tamoxifen plus radiotherapy (n = 317) or tamoxifen alone (n = 319). All women received tamoxifen at 20 mg per day for 5 years. “Adjuvant hormonal treatment beyond 5 years was discretionary,” the investigators stated.
At 10 years, “the incidence of locoregional recurrence is 8% lower, and the incidence of [ipsilateral breast recurrence] is 7% lower, with [tamoxifen plus radiotherapy] vs [tamoxifen] alone. This difference is statistically significant,” the authors wrote. Of the 32 women in the tamoxifen group who had locoregional recurrence, 20 had only ipsilateral breast recurrence; 6 had ipsilateral breast recurrence with distant metastasis; 5 had only axillary recurrence; and 1 had both ipsilateral breast recurrence and axillary recurrence. The six women in the tamoxifen-radiotherapy group who had locoregional recurrence all had ipsilateral breast recurrences.
Among the 33 patients experiencing ipsilateral breast recurrence, 10 of 27 in the tamoxifen group, and 4 of 6 in the tamoxifen-radiotherapy group had mastectomies. The time to mastectomy did not differ significantly between the two groups and the 10-year probability of not undergoing mastectomy was 98% in the tamoxifen-radiotherapy group and 96% in the tamoxifen-only group. Time to distant metastases also did not differ significantly between the two groups, and the 10-year probability of freedom from distant metastases was 95% in both groups.
A total of 334 deaths occurred, but only 21 as a result of breast cancer (13 of 166 deaths in the tamoxifen-radiotherapy group and 8 of 168 deaths in the tamoxifen-only group). Ten-year overall survival was 67% for tamoxifen-radiotherapy and 66% for tamoxifen only.
“The toxicity of tamoxifen is not trivial, particularly in this elderly population. Well-known adverse effects include hot flashes, thrombotic events, and a small risk of endometrial cancer,” the authors noted. “However, despite the possibility that all patients were not able to complete the prescribed course of treatment, local control, distant disease-free survival, and cancer-specific survival remained excellent in this population with generally favorable disease characteristics.” ■
Hughes KS, et al: J Clin Oncol. May 20, 2013 (early release online).