Electronic brachytherapy as adjuvant therapy for early stage breast cancer: a retrospective analysis

Abstract

Purpose:

This multicenter, retrospective study evaluated treatment and clinical outcomes of patients with early stage breast cancer who received adjuvant high-dose rate (HDR) electronic brachytherapy (EBT) treatment post-lumpectomy using the Axxent^® EBT system. Dosimetric data from the EBT treatment plans were compared with those based on iridium-192 HDR brachytherapy.

Material and methods:

Medical records of 63 patients with early stage breast cancer (Tis, T1a, T1b, T1c, and T2) who were treated post-lumpectomy with EBT alone or in combination with external beam radiation therapy were reviewed. The prescribed EBT dose was 34 Gy (10 fractions over 5 days, 3.4 Gy each) to 1 cm from the balloon surface. Dosimetry data from 12 patients were compared with these of treatment plans using an iridium-192 source prepared for the same 12 patients.

Results:

The majority of patients (90.5%) were older than 50 years and had one or more risk factors for breast cancer (80.6%). Tumor sizes were 0.1 cm to 3.5 cm (mean 1.3 cm). Median follow-up was 7 months (1 to 18 months) post-EBT. Balloon applicators were implanted 0 to 85 days (mean 13.4 days) post-lumpectomy/re-excision. The most common adverse events were erythema, rash dermatitis, and pain or breast tenderness. No recurrences were reported. Dosimetric analyses demonstrated comparable target coverage, increased high-dose regions, and a significantly reduced dose to the ipsilateral breast and lungs as well as the heart with EBT as compared with the iridium-192 treatment plans.

Conclusion:

This retrospective, multicenter study showed that postsurgical adjuvant radiation therapy for early stage breast cancer can be administered using the EBT system with similar toxicity outcomes to those reported with iridium-192 brachytherapy. EBT offers a convenient, portable, nonisotope alternative to HDR brachytherapy using iridium-192.

Keywords:

• electronic brachytherapy
• breast cancer
• radiation therapy

Acknowledgements

The authors wish to thank all research staff who supported this research. The authors would like to acknowledge Leslie Todd, medical writer, and Kathy L Warner, biostatistician, for their assistance with this manuscript.

Disclosure

Randall Holt is a medical physics director and paid consultant for Xoft, Inc. Charles Lee was compensated for his time required to create the treatment plans. Peter Beitsch is a co-principal investigator of a prospectively enrolling early stage breast cancer study funded by Xoft, Inc. This retrospective study was funded by Xoft, Inc.