Accelerated partial breast irradiation: current status and future directions

Abstract

Breast cancer is the most common cancer in women worldwide. Radiation therapy is an essential component in the management of breast cancer. With the advancement of screening mammogram, most breast cancers are diagnosed early, leading to excellent outcomes. Subsequently, this has led to the investigation of patient-centered treatment paradigms that would improve patient satisfaction and convenience. There have been multiple attempts to omit radiation therapy in appropriately selected early breast cancer, while some studies showed non-inferiority, there has always been at least local control advantage. Accelerated partial breast irradiation (APBI) has been studied in a number of clinical trials as an alternative to whole breast irradiation in women with early stage breast cancer with the rationale of decreasing treatment time and volume of tissue irradiated, while maintaining efficacy. There is no consensus on APBI optimal modality, dose, or schedule. This may be due to early trial results with a relatively shortterm follow-up showing conflicting outcomes regarding local control and treatment-related toxicities. However, there have been recently published APBI clinical trials reporting 10-years follow-up and with the ongoing coronavirus pandemic, the role of APBI in the treatment of early-stage breast cancer warrants further exploration. In this review, we will present the major APBI approaches: external beam radiation therapy (EBRT), brachytherapy (BT), and intra-operative radiation therapy (IORT). We will review modern trials of APBI, highlighting the larger trials with long-term follow-up.