[Role of irradiation in breast conservation therapy for breast cancer]

Despite a worldwide consensus on the indication for breast conservation therapy (BCT), the proportion of patients treated with BCT in Japan was only 29.2% in 1997. Indications of BCT and opinions against increasing the number of BCT in Japan are discussed along with the concept of evidence-based medicine (EBM). It is evident that in Japan as well, 70% to 90% of patients with breast cancer can be treated with BCT. The main aim of irradiation in BCT is to reduce inbreast recurrences (IBR), and randomized controlled trials have confirmed that irradiation to the breast reduces IBR. Currently, much concern is being directed to the issue of surgical margins in partial mastectomy, i.e., the definition of positivity of margins and how to treat margin-positive cases. The role of boost irradiation to the tumor bed and irradiation to lymph node areas are also discussed.