Breast cancer in young women and prognosis: How important are proliferation markers?

Aim: Compared to middle-aged women, young women with breast cancer have a higher risk of systemic disease. We studied expression of proliferation markers in relation to age and subtype and their association with long-term prognosis. Methods: Distant disease-free survival (DDFS) was studied in 504 women aged <40 years and 383 women aged >= 40 years from a population-based cohort. Information on patient characteristics, treatment and follow-up was collected from medical records. Tissue microarrays were produced for analysis of oestrogen receptor, progesterone receptor (PR), Her2, Ki-67 and cyclins. Results: Young women with luminal tumours had significantly higher expression of Ki-67 and cyclins. Proliferation markers were prognostic only within this subtype. Ki-67 was a prognostic indicator only in young women with luminal PR+ tumours. The optimal cut-off for Ki-67 varied by age. High expression of cyclin E1 conferred a better DDFS in women aged <40 years with luminal PR- tumours (hazard ratio [HR] 0.47 [0.24-0.92]). Age < 40 years was an independent risk factor of DDFS exclusively in women with luminal B PR+ tumours (HR 2.35 [1.22-4.50]). Young women with luminal B PR- tumours expressing low cyclin E1 had a six-fold risk of distant disease compared with luminal A ( HR 6.21 [2.17-17.6]). Conclusions: The higher expression of proliferation markers in young women does not have a strong impact on prognosis. Ki-67 is only prognostic in the subgroup of young women with luminal PR tumours. The only cyclin adding prognostic value beyond subtype is cyclin E1. Age is an independent prognostic factor only in women with luminal B PR+ tumours. (C) 2017 Elsevier Ltd. All rights reserved.