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Background: For women with ductal carcinoma in situ (DCIS), radiation therapy after conservative surgery lowers the risk of recurrence. However, emerging evidence suggests that radiation therapy confers only a marginal absolute benefit for older women with DCIS. In a cohort of older women with DCIS, we sought to determine whether radiation therapy was associated with a clinically significant benefit. Methods: Using the Surveillance, Epidemiology, and End Results (SEER)-Medicare database from January 1, 1992, through December 31, 1999, we identified 3409 women aged 66 years or older treated with conservative surgery for DCIS. A proportional hazards model tested whether radiation therapy was associated with a lower risk of a combined outcome, defined as a subsequent ipsilateral in situ or invasive breast cancer reported by SEER and/or a subsequent mastectomy reported by Medicare claims. The 5-year event risk was determined for patients without and with high-risk features, which were defined as at least one of the following: age 66–69 years, tumor larger than 2.5 cm, comedo histology, and/or high grade. All statistical tests were two-sided. Results: Radiation therapy was associated with a lower risk for each component of the combined outcome (hazard ratio = 0.32, 95% confidence interval [CI] = 0.24 to 0.44). For high-risk patients, the 5-year event risk was 13.6% without radiation therapy versus 3.8% with radiation therapy (difference = 9.8%, 95% CI = 6.5 to 13.2; P<.001). For low-risk patients, the 5-year event risk was 8.2% without radiation therapy versus 1.0% with radiation therapy (difference = 7.2%, 95% CI = 3.6 to 10.9; P<.001). Among healthy women aged 66–79 years, the number needed to treat with radiation therapy to prevent one event in 5 years was 11 for high-risk patients and 15–16 for low-risk patients. Conclusion: For older women with DCIS, radiation therapy appears to confer a substantial benefit that remains meaningful even among low-risk patients. [ABSTRACT FROM AUTHOR]

Background: Recent clinical trials have questioned the necessity of breast radiation therapy for older women with early breast cancer. However, the effectiveness of radiation therapy for older women in the community setting has not been addressed. Methods: We used the Surveillance, Epidemiology, and End Results (SEER)-Medicare database from January 1, 1992, through December 31, 1999, to identify 8724 women aged 70 years or older treated with conservative surgery for small, lymph node-negative, estrogen receptor-positive (or unknown receptor status) breast cancer. We used a proportional hazards model to test whether radiation therapy was associated with a lower risk of a combined outcome, defined as a second ipsilateral breast cancer reported by SEER and! or a subsequent mastectomy reported by Medicare claims. All statistical tests were two-sided. Results: Radiation therapy, compared with no radiation therapy, was associated with a lower risk of the combined outcome (hazard ratio = 0.19, 95% confidence interval = 0.14 to 0.28). Radiation therapy was associated with an absolute risk reduction of 4.0 events per 100 women at 5 years (i.e., from 5.1 events without radiation therapy to 1.! with radiation therapy) and 5.7 events per 100 persons at 8 years (i.e., from 8.0 events without radiation therapy to 2.3 with radiation therapy) (P<.001, log-rank test). Radiation therapy was most likely to benefit those aged 70-79 years without comorbidity (number needed to treat [NNT] to prevent one event = 21 to 22 patients) and was least likely to benefit those aged 80 years or older with moderate to severe comorbidity (NNT = 61 to 125 patients). Conclusion: For older women with early breast cancer, radiation therapy was associated with a lower risk of a second ipsilateral breast cancer and subsequent mastectomy. Patients aged 70-79 years with minimal comorbidity were the most likely to benefit, and older patients with substantial comorbidity were least likely to benefit. [ABSTRACT FROM AUTHOR]