15P - Pilot study on the use of a subcutaneous spacer injection in the breast for skin protection during brachytherapy

Date 04 May 2017
Event IMPAKT 2017
Session Welcome reception and Poster Walk
Topics Breast Cancer
Presenter Gerson Struik
Authors G.M. Struik1, A. Ghandi2, I.K. Kolkman-Deurloo3, E. Birnie4, J.P. Pignol5, T.M.A.L. Klem1
  • 1Surgery, Franciscus Gasthuis en Vlietland, 3000BA - Rotterdam/NL
  • 2Radiology, Franciscus Gasthuis en Vlietland, 3000BA - Rotterdam/NL
  • 3Radiation Oncology - Physics, Erasmus MC- Cancer Institute, 3008 AE - Rotterdam/NL
  • 4Department Of Statistics And Education, Franciscus Gasthuis en Vlietland, 3000BA - Rotterdam/NL
  • 5Radiation Oncology, Erasmus MC- Cancer Institute, 3008 AE - Rotterdam/NL

Abstract

Body

Introduction

Partial breast irradiation following breast conserving surgery has shown equal effectiveness as whole breast irradiation in a selected group of early stage breast cancer patients. Main side effect of all forms of brachytherapy is skin toxicity, with dose to the skin as main risk factor. Creating an extra 5mm between radiation source and the skin by injecting a subcutaneous spacer could reduce the skin dose to 50%.

Aim of this study was to investigate the principle of the spacer injection.

Patients and methods

A pilot study as a proof-of-principle of an intervention (ultrasound guided spacer injection) was performed on mastectomy specimen of women after mastectomy for breast cancer. Specimen with mastitis carcinomatosa were excluded. Two products were tested: hyaluronic acid gel (HA) (“Barrigel”) and iodined PolyEthyleneGlycol (PEG)(“TraceIT”). Success of the intervention was defined as creating a spacer thickness of ≥5mm subcutaneously in a marked circle with a 20mm radius. Measurement of spacer thickness was performed by ultrasound. Presence of a superficial fascial layer and possibility of hydrodissection were recorded. Ease of use was measured with the System Usability Scale (SUS). A CT-scan was made pre- and post-injection. Dosimetry analysis was performed by simulating a Clinical Target Volume on the fused CT-scans and perform a radiotherapy planning. Skin isodose was calculated with and without spacer.

Results

22 specimen were included for spacer injection; 11 HA, 11 PEG. Success of the intervention was 100% for HA and 90.9% for PEG (n.s.). A superficial fascial layer was present in 59.1% of the specimen. Mean injected volumes were 7.4ml for HA and 7.3 for PEG (n.s.). Hydrodissection was possible in 81.8% with HA and 63.6% with PEG (p<0.05). Mean SUS score was 96 for HA and 81 for PEG (p<0.05). Percentage of simulated skin isodose ≥85% was 90.9% without spacer and 4.5% with spacer (p<0.05) (0% with HA, 9.1% with PEG).

Conclusion

This pilot study shows a very high success rate of a subcutaneous spacer injection for skin protection during brachytherapy of the breast. A spacer thickness of ≥5mm can reduce the skin dose dramatically. Clinical evaluation of the effect on skin toxicity is needed.

Clinical trial identification

pre-clinical trial

declared NOT to be "Medical Research Involving Human Subjects Act (in Dutch: Wet Medisch-wetenschappelijk Onderzoek met Mensen" by the Ethical Commitee "Toetsingscommissie Wetenschappelijk Onderzoek Rotterdam" protocol T2016-34