Age-related variations in the use of axillary dissection: a survival analysis of 8038 women with T1-ST2 breast cancer.

PURPOSE: The use of axillary dissection (AD) in women with invasive breast cancer is increasingly questioned. This study analyzes the survival in women with T1-2 breast cancer according to age and AD use. METHODS AND MATERIALS: Data from the Breast Cancer Outcomes Unit Database were analyzed for 8038 women aged 50-89 years referred to the British Columbia Cancer Agency between 1989 and 1998 with invasive T1-2,M0 breast cancer. Tumor and treatment characteristics were compared between women treated with and without AD (AD+ vs. AD-) according to three age groups: 50-64, 65-74 and 75+ years. Regional relapse and actuarial 5-year overall and breast cancer-specific survival were compared between AD+ and AD- women. Multivariate analysis of age, tumor and treatment factors, and adjusted hazard ratios with AD omission were performed.
RESULTS: AD was omitted more frequently with advancing age (4% vs. 8% vs. 22% in women aged 50-64, 65-74, and 75+ years, respectively, p <0.0001). Tumor characteristics were more favorable in AD- women, with fewer having Grade III disease, T2 tumors, or lymphovascular invasion (all p <0.0001). Women treated without AD were also less likely to undergo radiotherapy after lumpectomy or mastectomy (both p <0.0001). Systemic therapy use and regional relapse rates were comparable between AD- and AD+ women in each age-specific cohort. Multivariate analysis identified age, tumor size, grade, lymphovascular invasion, estrogen receptor status, clinical nodal palpability, type of surgery, and radiotherapy use as independent variables affecting survival. Hazard ratios adjusted for these variables showed AD omission to be associated with lower overall survival in the entire cohort (hazard ratio 1.52, p <0.0001) and lower breast cancer-specific survival in women aged 65-74 years (hazard ratio 1.99, p = 0.02).
CONCLUSION: AD was more frequently omitted with advancing age. The lack of differences in systemic therapy use, regional relapse, and breast cancer-specific survival among AD- compared with AD+ women aged 75+ years suggests that AD use may be selectively omitted in this elderly cohort. However, the lower survival associated with AD omission among women aged 65-74 years, and the lack of a survival advantage among AD- women aged 50-64 years despite more favorable tumor characteristics and comparable systemic therapy use support the hypothesis that definitive locoregional therapy has an impact on survival.