Are breast conservation and mastectomy equally effective in the treatment of young women with early breast cancer? Long-term results of a population-based cohort of 1,451 patients aged ≤ 40 years.

To compare the effectiveness of breast-conserving therapy (BCT) and mastectomy, all women aged ≤ 40 years, treated for early-stage breast cancer in the southern part of the Netherlands between 1988 and 2005, were identified. A total of 562 patients underwent mastectomy and 889 patients received BCT. During follow-up, 23 patients treated with mastectomy and 135 patients treated with BCT developed a local relapse without previous or simultaneous evidence of distant disease. The local relapse risk for patients treated with mastectomy was 4.4% (95% confidence interval (CI) 2.4-6.4) at 5 years and reached a plateau after 6 years at 6.0% (95% CI 3.5-8.5). After BCT, the 5-, 10- and 15-year risks were 8.3% (95% CI 6.3-10.5), 18.4% (95% CI 15.0-21.8) and 28.2% (95% CI 23.0-33.4), respectively (P < 0.0001). Adjuvant systemic therapy following BCT reduced the 15-year local relapse risk from 32.9% (95% CI 26.7-39.1) to 16.1% (95% CI 9.1-23.1), (P = 0.0007). In conclusion, local tumor control in young patients with early-stage breast cancer is worse after BCT than after mastectomy. Adjuvant systemic therapy significantly improves local control following BCT and also for that reason it should be considered for most patients ≤ 40 years. Long-term follow-up is highly recommended for young patients after BCT, because even with systemic treatment an annual risk of local relapse of 1% remains up to 15 years after treatment.