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Title: SU-F-T-455: Is Contouring the Whole Breast Necessary for Two-Field 3D Breast Planning?

Abstract

Purpose: To investigate the effect of contouring the whole breast on reducing the radiation dose to the heart and affected lung in tangential field-in-field 3D breast planning. We hypothesize that contouring the whole breast will simplify the plan normalization process, reduce dose to critical structures, while maintaining treatment plan quality and consistency. Methods: Twenty previously treated breast cancer patients using tangential field-in-field 3D planning technique were randomly selected. The affected breast was contoured following the RTOG breast atlas guideline. Breast PTV was created by shrinking 5 mm from the breast contour. The same plan has been pasted to the new contour and normalized to 95% of the Breast PTV receiving the prescribed isodose line. Lung V20 Gy% and Heart V25 Gy% were the primary study endpoints. Homogeneity Index (HI) and Conformity Index (CI) were calculated based on the following equations. HI= Dmax/ D95 and Nakamura’s Conformity Index= PIV/TVPIV × TV/TVPIV. Results: The average CI for previous plans was 1.68 vs. 1.66 for the new hybrid plan: both plans were conformal to the breast with similar quality. The HI for both the previous and the new hybrid plan was 1.24. Lung V 20% slightly increased from 4.27% to 4.82%. Heart Vmore » 25% for LT breast patients slightly decreased from 0.38% to 0.29%. Heart V 25% for RT breast patients was close to zero in both cases. Conclusion: With similar conformal and homogeneity indices for the plan quality, by contouring the whole breast following RTOG breast atlas guideline will simplify the planning process. The study showed that contouring the whole breast for patients with left-sided breast cancer reduced the heart V 25%, although not significantly, while maintaining the CI and HI. There was no measurable gain seen with whole breast contour for right-sided breast cancer patients.« less

Authors:
;  [1]; ; ; ;  [2]
  1. Frank H Netter, MD, School of Medicine, North Haven, CT (United States)
  2. St. Vincent’s Medical Center, Bridgeport, CT (United States)
Publication Date:
OSTI Identifier:
22649046
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; HEART; LUNGS; MAMMARY GLANDS; NEOPLASMS; PATIENTS; PLANNING; RADIATION DOSES

Citation Formats

Desai, A, Ku, Eric, Fang, D, Lawrence, C, Iannuzzi, C, and Shi, C. SU-F-T-455: Is Contouring the Whole Breast Necessary for Two-Field 3D Breast Planning?. United States: N. p., 2016. Web. doi:10.1118/1.4956640.
Desai, A, Ku, Eric, Fang, D, Lawrence, C, Iannuzzi, C, & Shi, C. SU-F-T-455: Is Contouring the Whole Breast Necessary for Two-Field 3D Breast Planning?. United States. doi:10.1118/1.4956640.
Desai, A, Ku, Eric, Fang, D, Lawrence, C, Iannuzzi, C, and Shi, C. 2016. "SU-F-T-455: Is Contouring the Whole Breast Necessary for Two-Field 3D Breast Planning?". United States. doi:10.1118/1.4956640.
@article{osti_22649046,
title = {SU-F-T-455: Is Contouring the Whole Breast Necessary for Two-Field 3D Breast Planning?},
author = {Desai, A and Ku, Eric and Fang, D and Lawrence, C and Iannuzzi, C and Shi, C},
abstractNote = {Purpose: To investigate the effect of contouring the whole breast on reducing the radiation dose to the heart and affected lung in tangential field-in-field 3D breast planning. We hypothesize that contouring the whole breast will simplify the plan normalization process, reduce dose to critical structures, while maintaining treatment plan quality and consistency. Methods: Twenty previously treated breast cancer patients using tangential field-in-field 3D planning technique were randomly selected. The affected breast was contoured following the RTOG breast atlas guideline. Breast PTV was created by shrinking 5 mm from the breast contour. The same plan has been pasted to the new contour and normalized to 95% of the Breast PTV receiving the prescribed isodose line. Lung V20 Gy% and Heart V25 Gy% were the primary study endpoints. Homogeneity Index (HI) and Conformity Index (CI) were calculated based on the following equations. HI= Dmax/ D95 and Nakamura’s Conformity Index= PIV/TVPIV × TV/TVPIV. Results: The average CI for previous plans was 1.68 vs. 1.66 for the new hybrid plan: both plans were conformal to the breast with similar quality. The HI for both the previous and the new hybrid plan was 1.24. Lung V 20% slightly increased from 4.27% to 4.82%. Heart V 25% for LT breast patients slightly decreased from 0.38% to 0.29%. Heart V 25% for RT breast patients was close to zero in both cases. Conclusion: With similar conformal and homogeneity indices for the plan quality, by contouring the whole breast following RTOG breast atlas guideline will simplify the planning process. The study showed that contouring the whole breast for patients with left-sided breast cancer reduced the heart V 25%, although not significantly, while maintaining the CI and HI. There was no measurable gain seen with whole breast contour for right-sided breast cancer patients.},
doi = {10.1118/1.4956640},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • To determine whether small field boost (SFB) replanning is necessary when the lumpectomy cavity (LPC) decreases during whole-breast irradiation (WBI) and what parameters might predict a change in the SFB plan. Forty patients had computed tomography (CT) simulation (CT1) within 60 days of surgery and were resimulated (CT2) after 37.8-41.4 Gy for SFB planning. A 3-field photon plan and a single en face electron plan were created on both CTs and compared. In the 26 patients who had a {>=}5 cm{sup 3} and a {>=}25% decrease in lumpectomy cavity volume (LCV) between CT scans, the SFB plan using photons wasmore » different in terms of normal breast tissue volume irradiated (BTV) (p < 0.001), and field dimensions (p < 0.001). In 20/35 patients, the energy or field size changed for electron plans on CT2, but no tested characteristics predicted for a change. Less BTV was irradiated using electrons than photons in 29% (CT1) to 37% (CT2). SFB replanning needs to be individualized to each patient because of the variety of factors that can impact dosimetric planning. Replanning is recommended when using 3-field photons if the patient has experienced a {>=}5 cm{sup 3} and a {>=}25% decrease in LCV during WBI. Some patients may benefit from electron SFB replanning but no tested characteristics reliably predict those who may benefit the most. The amount of BTV irradiated is less with electrons than in photon plans and this has the potential to improve cosmesis, a clinically important outcome in breast-conserving therapy.« less
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