Where youth matters-clinicopathologic characteristics and emerging trends in treatment and outcomes in young Irish women with breast cancer.

Background: Young women with breast cancer (YWBC) represent 7-12% of breast cancer diagnoses and ostensibly have more biologically aggressive subtypes with higher relapse and mortality rates. We studied the clinical and pathological characteristics in YWBC and examined how outcomes and treatment have evolved.
Methods: YWBC were identified from pathology databases at two tertiary centers. Patients were divided into two cohorts: those diagnosed from 2000 to 2005 (C1) and from 2006 to 2015 (C2). Data were retrieved from clinical, radiology, and histology databases. Statistical analysis was performed using R® (V3.2.0).
Results: We identified 345 patients. Median age was 36 years (23-39 years). Mastectomy was performed in 232 patients (67.2%) and axillary lymph node clearance (ALNC) in 207 patients (60% [C1 82.7 vs. C2: 49.4%, p < 0.001]). One hundred-seventy patients (49%) were ER + HER2-, 88 (25.5%) were HER2+, and 58 (16.8%) were triple negative. Eighty patients (23.2%) received neoadjuvant therapy. Pathological complete response rates were statistically similar between C1 and C2 [C1 1 (0.9%) vs C2 16 (6.8%) p = 0.1]. Distant relapse occurred in 59 (19%) patients. There was a higher relapse rate (RR) in C1 [27 (32.1%) vs. 32 (15.7%), p < 0.002). HER2+ and ER+ HER2- patients in C1 had higher RRs than C2. Median overall survival in patients with metastatic disease was 29 months (range 2-119 months).
Conclusion: Locally advanced disease was more prevalent in YWBC. Mastectomy and ALNC rates were high and most received multimodal treatment. The extent of axillary surgery declined over time. Outcomes were unchanged in triple negative patients. These remain a priority for research.