Stereotactic Accelerated Partial Breast Irradiation for Early-Stage Breast Cancer: Rationale, Feasibility, and Early Experience Using the CyberKnife Radiosurgery Delivery Platform.

Olusola Obayomi-Davies,Thomas P Kole,Hozaifa M Anjum,Sonali Rudra,Sean P Collins,Eleni Tousimis,Brian T Collins,Shawna Willey,Erini V Makariou,Lloyd D Campbell,Bridget Oppong,Keith Unger

doi:10.3389/fonc.2016.00129

Abstract

The efficacy of accelerated partial breast irradiation (APBI) utilizing brachytherapy or conventional external beam radiation has been studied in early-stage breast cancer treated with breast-conserving surgery. Data regarding stereotactic treatment approaches are emerging. The CyberKnife linear accelerator enables excellent dose conformality to target structures while adjusting for target and patient motion. We report our institutional experience on the technical feasibility and rationale for stereotactic accelerated partial breast irradiation (SAPBI) delivery using the CyberKnife radiosurgery system. Ten patients completed CyberKnife SAPBI (CK-SAPBI) in 2013 at Georgetown University Hospital. Four gold fiducials were implanted around the lumpectomy cavity prior to treatment under ultrasound guidance. The synchrony system tracked intrafraction motion of the fiducials. The clinical target volume was defined on contrast enhanced CT scans using surgical clips and post-operative changes. A 5 mm expansion was added to create the planning treatment volume (PTV). A total dose of 30 Gy was delivered to the PTV in five consecutive fractions. Target and critical structure doses were assessed as per the National Surgical Adjuvant Breast and Bowel Project B-39 study. At least three fiducials were tracked in 100% of cases. The Mean treated PTV was 70 cm(3) and the mean prescription isodose line was 80%. Mean dose to target volumes and constraints are as follows: 100% of the PTV received the prescription dose (PTV30). The volume of the ipsilateral breast receiving 30 Gy (V30) and above 15 Gy (V > 15) was 14 and 31%, respectively. The ipsilateral lung volume receiving 9 Gy (V9) was 3%, and the contralateral lung volume receiving 1.5 Gy (V1.5) was 8%. For left-sided breast cancers, the volume of heart receiving 1.5 Gy (V1.5) was 31%. Maximum skin dose was 36 Gy. At a median follow-up of 1.3 years, all patients have experienced excellent/good breast cosmesis outcomes, and no breast events have been recorded. CyberKnife stereotactic accelerated partial breast irradiation is an appealing technique for partial breast irradiation offering improvements over existing APBI techniques. Our early findings indicate that CK-SAPBI delivered in five daily fractions is feasible, well tolerated, and is a reliable platform for delivering APBI.

Highlights

We report our institutional experience on the technical feasibility and rationale for stereotactic accelerated partial breast irradiation (SAPBI) delivery using the CyberKnife radiosurgery system
Breast-conserving therapy (BCT) is the preferred treatment approach for early-stage breast cancer and numerous randomized controlled studies have demonstrated equivalent overall survival for patients receiving breast-conserving surgery with whole breast irradiation (WBI) compared with patients treated by mastectomy alone [1,2,3,4]
We present our early institutional experience with the technical set-up, treatment planning, and dosimetric parameters of 10 patients receiving CK-SAPBI

Summary

Introduction

Breast-conserving therapy (BCT) is the preferred treatment approach for early-stage breast cancer and numerous randomized controlled studies have demonstrated equivalent overall survival for patients receiving breast-conserving surgery with whole breast irradiation (WBI) compared with patients treated by mastectomy alone [1,2,3,4]. These studies demonstrate ~70% reduction in local recurrence with the addition of adjuvant radiation after breastconserving surgery [5] and a reduction in the risk of breast cancer death by one-sixth at 15 years [6]. External beam APBI (EB-APBI) is subject to intra-fractional motion, surface deformation, and treatment set-up uncertainties that have to be accounted for with increases in the planning target volume (PTV) resulting in larger amounts of normal breast tissue receive highdose irradiation and increased risk of poor cosmesis [15,16,17]

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Results

Conclusion