'Dosimetric breast size': a new and useful parameter for the prediction of local recurrence after breast conservative treatment

Abstract

To evaluate the risk of local recurrence following breast-conserving therapy for breast cancer, we measured the distance between each entry point of the irradiation on the surface of the breast in line with the axis of the external and internal tangential fields (dosimetric breast size). 652 breast cancer patients were retrospectively analysed, with a median age of 51 years and a median follow-up of 99 months (range 84-192). There were 50 local recurrences, 44 isolated and 6 associated with nodal recurrence or metastases. The global rates of local recurrences at 5 and 10 years were 5.3% and 9%, respectively (Kaplan-Meier analysis). Following a Cox's multivariate analysis, the only significant and independent parameters related to local recurrence were quality of excision, age at diagnosis and dosimetric breast size. For a small dosimetric breast size (< or = 10 cm), the rate of local recurrence was 14.1 compared with 11.8 for medium dosimetric breast size (> 10 cm-< or = 12 cm) and 5.2 for large dosimetric breast size (> 12 cm). If the analysis was restricted to only those with complete excision, then the relative risk for a patient with a small dosimetric breast size was three times that for a large breast size.