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Assessment of Irregular Surface Compensator Technique for Deep Inspiration Breath-Hold (DIBH) Left-Side Breast Radiation

J Peng

J Peng*, C Mart , M Ashenafi , D McDonald , N Koch , J Harper , K Vanek , Medical University of South Carolina, Charleston, SC


SU-I-GPD-T-490 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: With the increasing use of deep inspiration breath hold(DIBH) techniques for left-sided breast cancer to reduce the heart toxicity, treatment efficiency could be the significant factor to impact the treatment accuracy of DIBH technique. The aim of this study was to determine the optimal technique for DIBH left-breast irradiation, with a focus on irregular surface compensator(ISC).

Methods: Ten DIBH left breast cases were randomly selected. Each case was contoured following guidelines included in the RTOG1304 protocol, and planned using both field-in-field(FIF) and ISC techniques. ISC is a tool in Eclipse which enables improved dose homogeneity for irregular shapes. The fluence distribution required to produce a planar dose perpendicular to the central axis at a specified depth and then delivered using a dynamic MLC field. The fluence value of the superficial region is also applied in order to ease MLC movement in the flash region. A prescription dose of 42.56Gy delivered in 16 fractions was used for all cases. Plans were compared and evaluated by several dose metrics as well as the treatment time. Differences were assessed for statistical significance(p<0.05) by use of Student's t-test.

Results: For targets, both plans exhibited similar coverage(V95%).ISC significantly improved the dose homogeneity index, and the maximum dose. Additionally, ISC provided slightly lower mean heart dose than FIF(2.7Gy v.s.3.1Gy,p=0.05).ISC also reduced V20Gy of the ipsilateral lung(18% v.s.22%).Finally, because of the dynamic MLC delivery, the ISC reduced the delivery time by 55% and the breath hold time by 40% per field as compared to FIF.

Conclusion: ISC technique not only guarantees skin flash, but also offers improved plan efficiency, better normal tissue sparing, and shorter treatment time compared to FIF.With the shorter delivery time, patient motion associated with breath hold is also reduced.The ISC technique is a suitable replacement for FIF in DIBH left-side breast treatment.

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