Long-term follow-up of Cancer and Leukemia Group B (CALGB) trial 9343 confirmed and extended 5-year results 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, even though it provides a small decrease” in ipsilateral breast recurrence. Reporting their results in the Journal of Clinical Oncology, the CALGB investigators concluded that “depending on the value placed on local recurrence,” tamoxifen without radiation “remains a reasonable option for women age ≥ 70 years with ER-positive early-stage breast cancer.”
A total of 636 women treated by lumpectomy were randomly assigned to receive tamoxifen plus radiation therapy (317 women) or tamoxifen alone (319 women). The investigators found that at 10 years follow-up, 98% of patients receiving tamoxifen plus radiation therapy (95% confidence interval [CI] = 96%–99%) vs 90% of those receiving tamoxifen alone (95% CI = 85%–93%) were free from local and regional recurrences. This 8% difference was considered statistically significant. Overall survival at 10 years was 67% (95% CI = 62%–72%) in the tamoxifen plus radiation therapy group and 66% (95% CI = 61%–71%) in the tamoxifen alone group.
“The addition of [radiation therapy] seems to provide no benefit in terms of [overall survival], distant disease-free survival, or ultimate breast preservation, with the proviso that the study lacked the power to definitively show noninferiority of either arm,” the authors noted. “Importantly, the study also shows that the impact of breast cancer in this select group of older women is much smaller than that of comorbid conditions. Of the 636 women in this study, only 21 (3%) have died as a result of breast cancer, whereas 313 (49%) have died as a result of other causes (only 6% of deaths attributed to breast cancer).”
The investigators also pointed out that the definition of negative margin has changed since the study began in 1994, with the current trend being toward greater negative margins (usually 1–2 mm), They noted that the low rate of ipsilateral breast recurrence without radiation therapy in this study “might further decrease with wider excision, suggesting that any benefit of [radiation therapy] over antiestrogen treatment alone in local recurrence may be of even less significance today.”
“We applaud the CALGB investigators for providing the oncology community with phase III data suggesting that selected elderly patients with ER-positive, early-stage disease being treated with hormonal therapy may not need breast radiation,” Benjamin D. Smith, MD, and Thomas A. Buccholz, MD, of The University of Texas MD Anderson Cancer Center in Houston, wrote in an accompanying editorial. “We support this conclusion for patients age 75 or older with low- to intermediate-grade disease and those with shorter life expectancies as a result of comorbidities. However, we feel that radiation use continues to be appropriate for patients younger than age 75 and those with high grade tumors.” ■