Emerging trends in radiation therapy use among women older than age 70 with stage I breast cancer from 2000-2007: A population-based analysis.

Abstract

6094 Background: The use of radiation therapy (RT) after lumpectomy is the standard of care in breast conserving therapy (BCT). A randomized trial published in 2004 suggested that women age ≥70 years with stage I, estrogen receptor (ER) positive breast cancer may not require RT after lumpetomy. We performed a population-based analysis to evaluate changes in patterns of RT usage among women age ≥70 from 2000-2007. Methods: We used the Surveillance, Epidemiology and End Results (SEER) database to identify women diagnosed with stage I invasive ductal breast cancer from 2000 – 2007 who were treated with lumpectomy. We extracted information on patient demographics, tumor characteristics, initial treatment course, and survival. Patients were classified by modality of RT: beam radiation, radioactive implant, other, or none. We used chi-square test for differences in proportion of RT modality usage and linear regression to test for trends in usage. Results: We identified 18,789 women age ≥ 70 (median age 77, range 70-108) diagnosed with stage I breast cancer from 2000 – 2007 and treated with lumpectomy. Overall, 62.8% of these women received external beam RT, 3.2% implant RT, 5.5% other RT, and 28.5% omitted RT. From 2000 to 2007, there has been a decrease in the use of external beam RT from 68.5% to 55.9% (p<0.001) and a simultaneous rise in the use of radioactive implants from 0.5% to 7.7% (p<0.001). Large geographic variations in utilization exist across SEER regions, such as in the percentage of older women who omit RT, from 15.1% (Seattle) to 42.3% (Los Angeles). For patients with known ER status, those with ER positive tumors were more likely to omit RT than those with ER negative tumors (26.9% vs 23.8% p = 0.02). Since 2000, the percentage of older women with ER positive tumors who receive no RT has increased from 24.4% to 29.5% (p=0.02). In contrast, the percentage of older women with ER negative cancers who received no RT did not significantly change. Conclusions: Patterns of RT usage in BCT for women ≥ 70 years with stage I breast cancer are changing with increasing use of radioactive implants and more patients with ER positive tumors omitting RT. Further follow-up is required to determine the effect on survival.