Comparison of breast‐conserving therapy vs mastectomy in women under age 40: National trends and potential survival implications

INTRODUCTION: Despite initial increased rates of breast-conserving therapy compared to mastectomy after 1990, mastectomy rates have increased in women under age 40 since 2000. Our study explores the demographic and survival implications of this trend. METHODS: The National Cancer Database was used to study stage 1 breast cancer diagnosed in women under age 40 between 2004 and 2014. Demographic and clinical data were obtained. Multivariable regression and survival analyses were performed. RESULTS: Of 11 859 patients under age 40, 57.2% underwent mastectomy (39.0% unilateral and 61.0% bilateral) rather than breast-conserving therapy (42.8%). The rate of mastectomy was significantly higher in 2014 compared to 2004 (43.6% in 2004 vs 62.4% in 2014; P < 0.001). The rate of bilateral mastectomy was significantly higher in 2014 compared to 2004 in contrast to unilateral mastectomy (31.7% in 2004 vs 73.0% in 2014; P < 0.001). Non-Hispanic Caucasian ethnicity and private insurance status were predictors of bilateral mastectomy (OR 2.06 [95% CI: 1.84-2.30], P < 0.001; OR 1.39 [95% CI: 1.21-1.59], P < 0.001). Controlling for demographics, tumor grade, and adjuvant therapies, bilateral mastectomy was associated with significantly increased 10-year survival vs unilateral mastectomy (HR 0.75 [0.59-0.96], P = 0.023). Additionally, breast-conserving therapy was associated with significantly increased 10-year survival vs unilateral (HR 2.36 [95% CI: 1.83-3.05]; P < 0.001) and bilateral mastectomy (HR 2.30 [95% CI: 1.61-3.27]; P < 0.001). CONCLUSIONS: The majority of women under age 40 with stage 1 invasive breast cancer underwent mastectomy instead of breast-conserving therapy. This largely reflects increased rates of contralateral prophylactic mastectomy. Bilateral mastectomy and breast-conserving therapy vs unilateral mastectomy were associated with a small but significant increase in survival. This finding warrants further investigation to determine the clinical implications of decision-making in younger women.