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

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.