Background: Breast-conserving therapy including lumpectomy and adjuvant whole breast
irradiation (WBI) has become the standard therapy for early-stage breast cancer (EBC).
Without WBI, the recurrence rate is significantly increased. However, when selecting
patients at a low a priori risk of local recurrence only a small breast-cancer-specific
mortality benefit, but no overall survival improvement, was detected for WBI. As most
recurrences occur close to the lumpectomy cavity, accelerated partial breast irradiation
(APBI) delivered exclusively to a limited volume of tissue around the initial lumpectomy
site, has gained increased attention and is now discussed as an alternative to WBI
for selected EBC patients. Summary: Numerous techniques for APBI (interstitial brachytherapy,
external beam-based APBI, intraoperative radiotherapy, MR-guided radiotherapy) allow
treatment delivery in a shorter period of time, and radiation oncologists expect to
further reduce side effects by using these new techniques, with improvements in cosmetics
and quality of life. In this review, we aim to describe the existing evidence for
the feasibility and effectiveness of different APBI techniques used in modern radiotherapy.
Key Messages: APBI has provided outcomes similar to WBI combined with potentially
reduced toxicity. While appropriate patient selection persists to be crucial for acceptable
recurrence rates, the precise definition of patients suitable for APBI remains a matter
of discussion. As long-term data are often still lacking, special attention should
be paid to late side effects and long-term outcomes. Decision-making on appropriate
treatment techniques should take into account not only local control rates, but also
the impact on the patient's quality of life.