Can patient-, treatment- and pathology-related characteristics explain the high local recurrence rate following breast-conserving therapy in young patients?

The aim of this study was to identify patient-, tumour- or treatment-related factors associated with young age that might explain the higher risk of ipsilateral breast recurrence that occurs after breast-conserving therapy (BCT) in young breast cancer patients. In the 'boost versus no boost trial', 5569 early-stage breast cancer patients were entered. All patients underwent tumorectomy followed by whole breast irradiation of 50 Gy. Patients having a microscopically complete excision were randomised between receiving no boost or a 16-Gy boost, while patients with a microscopically incomplete excision were randomised between receiving a boost dose of 10 or 26 Gy. The 5-year local control rate was 82% for patients less than or equal to 35 years, 85% for patients aged 36-40 years, 92% for patients 41-50 years, 96% for patients 51-60 years and 97% for patients > 60 years of age (P < 0.000 1). In young patients, the tumour was significantly larger and more often oestrogen and progesterone receptor-negative. Invasive carcinoma and the intraductal component were more often of a high grade. The intraductal component was more frequently incompletely resected in young patients. Re-excisions were performed more often (most probably due to a more frequent incomplete excision at the first attempt). The total volume of breast tissue removed at the tumorectomy was smaller in the younger patient group, even after including the volume removed during re-excision. When relating all these parameters (including age itself) to local control, the multivariate analysis stratified by treatment showed that age was the only independent prognostic factor for local control (P=0.0001). Including the boost treatment as a separate covariate, the analysis retained age and boost treatment as significant factors related to local control (P < 0.0001). It was shown that the boost dose significantly reduced the 5-year local recurrence rate from 7 to 4% for patients with a complete excision (P < 0.001). For patients 40 years of age or younger, the boost dose reduced the local recurrence rate from 20 to 10% (P=0.002). This large European Orgnaization for Research and Treatment of Cancer (EORTC) trial demonstrated an increased local recurrence rate in young patients. Although several associations between patient, tumour and treatment factors and age were found, that might explain the high local recurrence rate in the younger patients, it appears that age itself and the boost dose were the only factors that were independently related to local control. (C) 2003 Elsevier Science Ltd. All rights reserved.