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Vol 16, No 3 (2011)
Published online: 2011-05-01
Submitted: 2010-12-06
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Comparison of dose distributions and organs at risk (OAR) doses in conventional tangential technique (CTT) and IMRT plans with different numbers of beam in left-sided breast cancer

Hande Bas Ayata, Metin Güden, Cemile Ceylan, Nadir Kücük, Kayihan Engin
DOI: 10.1016/j.rpor.2011.02.001
·
Rep Pract Oncol Radiother 2011;16(3):95-102.

open access

Vol 16, No 3 (2011)
Published online: 2011-05-01
Submitted: 2010-12-06

Abstract

Aim

Our aim was to improve dose distribution to the left breast and to determine the dose received by the ipsilateral lung, heart, contralateral lung and contralateral breast during primary left-sided breast irradiation by using intensity modulated radiotherapy (IMRT) techniques compared to conventional tangential techniques (CTT). At the same time, different beams of IMRT plans were compared to each other in respect to CI, HI and organs at risk (OAR) dose.

Background

Conventional early breast cancer treatment consists of lumpectomy followed by whole breast radiation therapy. CTT is a traditional method used for whole breast radiotherapy and includes standard wedged tangents (two opposed wedged tangential photon beams). The IMRT technique has been widely used for many treatment sites, allowing both improved sparing of normal tissues and more conformal dose distributions. IMRT is a new technique for whole breast radiotherapy. IMRT is used to improve conformity and homogeneity and used to reduce OAR doses.

Materials and methods

Thirty patients with left-sided breast carcinoma were treated between 2005 and 2008 using 6, 18 or mixed 6/18 MV photons for primary breast irradiation following breast conserving surgery (BCS). The clinical target volume [CTV] was contoured as a target volume and the contralateral breast, ipsilateral lung, contralateral lung and heart tissues as organs at risk (OAR). IMRT with seven beams (IMRT7), nine beams (IMRT9) and 11 beams (IMRT11) plans were developed and compared with CTT and among each other. The conformity index (CI), homogeneity index (HI), and doses to OAR were compared to each other.

Results

All of IMRT plans significantly improved CI (CTT: 0.76; IMRT7: 0.84; IMRT9: 0.84; IMRT11: 0.85), HI (CTT: 1.16; IMRT7: 1.12; IMRT9: 1.11; IMRT11: 1.11), volume of the ipsilateral lung receiving more than 20[[ce:hsp sp="0.25"/]]Gy (>V20[[ce:hsp sp="0.25"/]]Gy) (CTT: 14.6; IMRT7: 9.08; IMRT9: 8.10; IMRT11: 8.60), and volume of the heart receiving more than 30[[ce:hsp sp="0.25"/]]Gy (>V30[[ce:hsp sp="0.25"/]]Gy) (CTT: 6.7; IMRT7: 4.04; IMRT9: 2.80; IMRT11: 2.98) compared to CTT. All IMRT plans were found to significantly decrease >V20[[ce:hsp sp="0.25"/]]Gy and >V30[[ce:hsp sp="0.25"/]]Gy volumes compared to conformal plans. But IMRT plans increased the volume of OAR receiving low dose radiotherapy: volume of contralateral lung receiving 5 and 10[[ce:hsp sp="0.25"/]]Gy (CTT: 0.0–0.0; IMRT7: 19.0–0.7; IMRT9: 17.2–0.66; IMRT11: 18.7–0.58, respectively) and volume of contralateral breast receiving 10[[ce:hsp sp="0.25"/]]Gy (CTT: 0.03; IMRT7: 0.38; IMRT9: 0.60; IMRT11: 0.68). The differences among IMRT plans with increased number of beams were not statistically significant.

Conclusion

IMRT significantly improved conformity and homogeneity index for plans. Heart and lung volumes receiving high doses were decreased, but OAR receiving low doses was increased.

Abstract

Aim

Our aim was to improve dose distribution to the left breast and to determine the dose received by the ipsilateral lung, heart, contralateral lung and contralateral breast during primary left-sided breast irradiation by using intensity modulated radiotherapy (IMRT) techniques compared to conventional tangential techniques (CTT). At the same time, different beams of IMRT plans were compared to each other in respect to CI, HI and organs at risk (OAR) dose.

Background

Conventional early breast cancer treatment consists of lumpectomy followed by whole breast radiation therapy. CTT is a traditional method used for whole breast radiotherapy and includes standard wedged tangents (two opposed wedged tangential photon beams). The IMRT technique has been widely used for many treatment sites, allowing both improved sparing of normal tissues and more conformal dose distributions. IMRT is a new technique for whole breast radiotherapy. IMRT is used to improve conformity and homogeneity and used to reduce OAR doses.

Materials and methods

Thirty patients with left-sided breast carcinoma were treated between 2005 and 2008 using 6, 18 or mixed 6/18 MV photons for primary breast irradiation following breast conserving surgery (BCS). The clinical target volume [CTV] was contoured as a target volume and the contralateral breast, ipsilateral lung, contralateral lung and heart tissues as organs at risk (OAR). IMRT with seven beams (IMRT7), nine beams (IMRT9) and 11 beams (IMRT11) plans were developed and compared with CTT and among each other. The conformity index (CI), homogeneity index (HI), and doses to OAR were compared to each other.

Results

All of IMRT plans significantly improved CI (CTT: 0.76; IMRT7: 0.84; IMRT9: 0.84; IMRT11: 0.85), HI (CTT: 1.16; IMRT7: 1.12; IMRT9: 1.11; IMRT11: 1.11), volume of the ipsilateral lung receiving more than 20[[ce:hsp sp="0.25"/]]Gy (>V20[[ce:hsp sp="0.25"/]]Gy) (CTT: 14.6; IMRT7: 9.08; IMRT9: 8.10; IMRT11: 8.60), and volume of the heart receiving more than 30[[ce:hsp sp="0.25"/]]Gy (>V30[[ce:hsp sp="0.25"/]]Gy) (CTT: 6.7; IMRT7: 4.04; IMRT9: 2.80; IMRT11: 2.98) compared to CTT. All IMRT plans were found to significantly decrease >V20[[ce:hsp sp="0.25"/]]Gy and >V30[[ce:hsp sp="0.25"/]]Gy volumes compared to conformal plans. But IMRT plans increased the volume of OAR receiving low dose radiotherapy: volume of contralateral lung receiving 5 and 10[[ce:hsp sp="0.25"/]]Gy (CTT: 0.0–0.0; IMRT7: 19.0–0.7; IMRT9: 17.2–0.66; IMRT11: 18.7–0.58, respectively) and volume of contralateral breast receiving 10[[ce:hsp sp="0.25"/]]Gy (CTT: 0.03; IMRT7: 0.38; IMRT9: 0.60; IMRT11: 0.68). The differences among IMRT plans with increased number of beams were not statistically significant.

Conclusion

IMRT significantly improved conformity and homogeneity index for plans. Heart and lung volumes receiving high doses were decreased, but OAR receiving low doses was increased.

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Keywords

Breast cancer; IMRT; Left breast; Whole breast radiotherapy; IMRT; Conventional techniques comparison

About this article
Title

Comparison of dose distributions and organs at risk (OAR) doses in conventional tangential technique (CTT) and IMRT plans with different numbers of beam in left-sided breast cancer

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 16, No 3 (2011)

Pages

95-102

Published online

2011-05-01

DOI

10.1016/j.rpor.2011.02.001

Bibliographic record

Rep Pract Oncol Radiother 2011;16(3):95-102.

Keywords

Breast cancer
IMRT
Left breast
Whole breast radiotherapy
IMRT
Conventional techniques comparison

Authors

Hande Bas Ayata
Metin Güden
Cemile Ceylan
Nadir Kücük
Kayihan Engin

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