Breast Cancer

, 7:231 | Cite as

Determination of optimal radiation energy for different breast sizes using ct-simulatior in tangential breast irradiation

  • Keiji Nihei
  • Michihide Mitsumori
  • Takashi Ishigaki
  • Satsuki Fujishiro
  • Masaki Kokubo
  • Yasushi Nagata
  • Keisuke Sasai
  • Masahiro Hiraoka
Original Article
Received:
Accepted:

Abstract

Background

The purpose of this study is to determine and recommend the optimal radiation source according to breast size for tangential irradiation in breast conserving therapy.

Methods

Twenty-eight patients treated at our department from January 1994 to January 1996 were studied. The dose distribution within the irradiated breast was calculated using ap60Co-gamma ray and 6 MV-X ray. Then we compared 3-D dose distributions of thep60Co-gamma ray and 6 MV-X ray in differentsized breasts. Three parameters (breast volume, chest wall separation, and breast height) were adopted as representative of breast size. We also examined correlations among the three parameters.

Results

When the breast size was large (breast volume>400 cmp3, chest wall separation >19.5 cm, or breast height>6.5 cm), the average volume of normal tissue which received more than 110% of the isocenter dose (“hot spot”) was significantly greater with thep60Co-gamma ray than with the 6 MV-X ray (p<0.05). A similar result was obtained with regard to hot spots in the clinical target volume. The cold area that received less than 95% of the isocenter dose was greater using a 6 MV-X ray when the breast size was small (breast volume <200 cmp3, chest wall separation< 17.5 cm, or breast height <5.0 cm). However, the difference was not significant.

There was a significant correlation between breast volume and chest wall separation (r=0.849, p< 0.001). Breast volume and breast height were also significantly correlated (r=0.813, p<0.001).

Conclusions

Since breast volume and shape are different in each patient, the optimal energy should be selected for each case to obtain uniform dose distribution in breast-conserving therapy. Chest wall separation or breast height, which are measurable without a 3-D planning system, can substitute for breast volume as parameters for breast size. We recommend that thep60Co-gamma ray not be used for treating large breasts, those with chest wall separation>/= 19.5 cm or breast height>/=6.5 cm.

Key words

Breast cancer Breast conserving therapy Radiotherapy Dose distribution CT-simulator Radiation energy Breast size 

Abbreviations

BCT

Breast conserving therapy

CT

Computed tomography

DVH

Dose volume histogram

CTV

Clinical target volume

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Copyright information

© The Japanese Breast Cancer Society 2000

Authors and Affiliations

  • Keiji Nihei
    • 1
  • Michihide Mitsumori
    • 1
  • Takashi Ishigaki
    • 2
  • Satsuki Fujishiro
    • 1
  • Masaki Kokubo
    • 1
  • Yasushi Nagata
    • 1
  • Keisuke Sasai
    • 1
  • Masahiro Hiraoka
    • 1
  1. 1.Department of Therapeutic Radiology and OncologyGraduate School of Medicine, Kyoto UniversityJapan
  2. 2.Department of RadiologyOsaka Red Cross HospitalJapan

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