Accelerated partial breast irradiation by brachytherapy: present evidence and future developments

Area of Science:

• Oncology
• Radiation Oncology
• Surgical Oncology

Background:

• Accelerated partial breast irradiation (APBI) is a targeted radiation therapy for breast cancer.
• APBI offers reduced treatment time and better sparing of healthy tissues compared to whole breast irradiation (WBIR).
• Effective APBI requires specialized surgical and radiation oncology collaboration and precise tumor bed marking.

Purpose of the Study:

• To review level 1 evidence for APBI techniques.
• To present long-term data from multi-institutional phase II studies.
• To discuss emerging ultra-short or single-fraction APBI courses and new brachytherapy sources.

Main Methods:

• Review of randomized controlled trials (RCTs) comparing APBI techniques with conventionally fractionated WBIR.
• Analysis of mature data from three RCTs.
• Evaluation of long-term patient-reported outcomes (PROs) and toxicity data.

Main Results:

• Multicatheter interstitial brachytherapy (MIBT)-APBI and intensity-modulated radiotherapy (IMRT)-APBI demonstrated noninferior local control and overall survival compared to WBIR.
• MIBT-APBI showed superior toxicity and PROs compared to WBIR at long-term follow-up.
• Other APBI techniques (intraoperative electrons, 50-kV x-rays, 3D-CRT) failed to show noninferiority to conventionally fractionated WBIR, though 3D-CRT-APBI was noninferior to hypofractionated WBIR but with higher toxicity.

Conclusions:

• MIBT-APBI is the only modality with noninferior survival and superior toxicity/PROs at 10 years.
• MIBT-APBI should be prioritized for low-risk breast cancer patients based on current international guidelines.
• Further research into ultra-short and single-fraction APBI courses is ongoing.