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  4. In-Vivo Skin Dosimetry Using the Novel CARA Breast Support for Supine Adjuvant Whole Breast Radiotherapy

In-Vivo Skin Dosimetry Using the Novel CARA Breast Support for Supine Adjuvant Whole Breast Radiotherapy

E Carpentier1,2*, E Facchin2 , J Yanchuk3 , B Gill2 , C Duzenli1,2 , (1) University of British Columbia, Vancouver, BC, Canada, (2) BC Cancer, Vancouver, BC, Canada, (3) BC Cancer, Kelowna, BC, Canada

Presentations

(Tuesday, 7/16/2019) 1:45 PM - 3:45 PM

Room: Stars at Night Ballroom 4

Purpose: Here we report on in-vivo skin dose measurements for a 20 patient pilot study using the novel CARA (Carbon-fibre Adjustable Reusable Accessory) breast positioning device, developed in house, for supine positioning in whole breast radiotherapy.

Methods: The CARA was used for simulation, planning, and treatment of women with large, pendulous breasts with an infra-mammary skin fold of 1 cm or more. Patients received whole breast radiation treatment with or without regional lymph nodes using tangents alone or tangents plus axilla and supraclavicular fields. Treatment was delivered using a step and shoot IMRT technique for prescribed doses to the breast of 42.5 Gy in 16 fractions or 50 Gy in 25 fractions, using combinations of 6 MV and 10 MV x-rays. A GafChromicâ„¢ film procedure was developed to measure skin dose to the inferior and lateral sides of the breast while supported by the CARA. Dose was measured on three treatment fractions using GafChromicâ„¢ film lining the inside of the CARA support in contact with the breast. This methodology provides a good estimate of the dose to the basal layer of the epidermis. Breast skin dose area histogram data for 70% to 110% of the prescribed dose is reported here.

Results: Differential dose area histogram data showed the area of skin receiving 100% of the prescribed dose was less than 1 cm² for all patients measured to date. The area of skin receiving 80% or more of the prescribed dose ranged from 4.6 cm² ± 2.1 cm² to 81.4 cm² ± 15.3 cm².

Conclusion: In-vivo breast skin dose can be reproducibly measured using this technique. The technique will be used in an upcoming clinical trial to assess the clinical impact of using the CARA for breast support.

Funding Support, Disclosures, and Conflict of Interest: Funding support from the Canadian Cancer Society US Provision Patent Number 6246494

Keywords

In Vivo Dosimetry, Breast, Film

Taxonomy

TH- Radiation dose measurement devices: Radiochromic film

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