Impact of established prognostic factors and molecular subtype in very young breast cancer patients: pooled analysis of four EORTC randomized controlled trials

Data from four European Organisation for Research and Treatment of Cancer (EORTC) clinical trials were pooled, resulting in a dataset consisting of 9,938 early breast cancer patients with a median follow-up of 11 years. For 549 patients aged less than 40 years at the time of diagnosis, including 341 node negative patients who did not receive chemotherapy, paraffin tumor blocks were processed for immunohistochemistry using a tissue microarray. Cox proportional hazard analysis was applied to assess the association of clinical and pathological factors with overall and distant metastasis free survival.For young patients, tumor size (P = 0.01), nodal status (P = 0.006) and molecular subtype (P = 0.02) were independent prognostic factors for overall survival. In the node negative subgroup, only molecular subtype was a prognostic factor for overall survival (P = 0.02). Young node negative patients bearing luminal A tumors had an overall survival rate of 94% at 10 years' follow-up compared to 72% for patients with basal-type tumors.Molecular subtype is a strong independent prognostic factor in breast cancer patients younger than 40 years of age. These data support the use of established prognostic factors as a diagnostic tool to assess disease outcome and to plan systemic treatment strategies in young breast cancer patients.The incidence of early stage breast cancer in young women is increasing. At present, breast cancer at a young age, that is, less than 40 years, accounts for approximately 5 to 7.5% of the total number of cases diagnosed each year in Western Europe and the US [1-3]. Based upon multiple retrospective analyses that demonstrated the unfavorable impact of young age on prognosis in breast cancer, several current consensus guidelines have included age ≥ 35 years as an absolute indication for adjuvant systemic chemotherapy irrespective of other tumor characteristics [4-6]. These guidelines imply that for young patients with favorable tumor features such as small