Stereotactic Body Radiotherapy: A Practical Guide for the Delivery of Accelerated Partial Breast Irradiation

Post-operative whole-breast irradiation (WBI) has been used in the last several decades to offer early-stage breast cancer patients options to preserve their breasts. The standard traditional external beam radiation treats the whole breast over a 6–7 week course; however, it is inconvenient and does have potential toxicity to heart, lung, bone, and soft tissues. Over the last decade, accelerated partial breast irradiation (APBI) allows the majority of these patients an attractive alternative to traditional radiation by treating part of the breast over 1–2 weeks. There are more than a dozen APBI techniques emerging over the last decade using various modalities of radiation including superficial X-ray, high-energy photon, proton beam, high-dose rate and low dose-rate brachytherapy. Of these, stereotactic body radiation therapy (SBRT) is an attractive option and is the focus of this chapter. SBRT offers patients the delivery ease of external beam radiotherapy (reproducibility factor) without the protracted time commitment seen with WBI (convenience factor). In addition, SBRT offers increased accuracy of irradiation delivery (target precision factor) without the inherent invasiveness (quality-of-life factor) of a brachytherapy implant. These SBRT abilities will likely increase the number of candidates for APBI, particularly those patients with difficult to treat anatomy (large/pendulous breasts), busy working women, elderly or disabled patients and those who live far from a radiation therapy clinic. This chapter describes one technique of SBRT for APBI using the CyberKnife system and preliminary data on a small group of patients demonstrates the feasibility and minimal side effects. More clinical studies need to be conducted to explore this new technique with end points of in-breast tumor recurrence, cost effectiveness, and quality of life endpoints including cosmesis, side effects and perceived convenience.