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LETTERS TO EDITOR
Year : 2017  |  Volume : 42  |  Issue : 2  |  Page : 99
 

Reference to: Chen YG, Li AC, Li WY, Huang MY, Li XB, Chen MQ, et al. The feasibility study of a hybrid coplanar arc technique versus hybrid intensity-modulated radiotherapy in treatment of early-stage left-sided breast cancer with simultaneous-integrated boost. J Med Phys 2017;42:1-8


Department of Radiation Oncology, Fortis Memorial Research Institute, Gurgaon, Haryana, India

Date of Web Publication16-Jun-2017

Correspondence Address:
Biplab Sarkar
Department of Radiation Oncology, Fortis Memorial Research Institute, Gurgaon, Haryana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jmp.JMP_37_17

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How to cite this article:
Sarkar B. Reference to: Chen YG, Li AC, Li WY, Huang MY, Li XB, Chen MQ, et al. The feasibility study of a hybrid coplanar arc technique versus hybrid intensity-modulated radiotherapy in treatment of early-stage left-sided breast cancer with simultaneous-integrated boost. J Med Phys 2017;42:1-8. J Med Phys 2017;42:99

How to cite this URL:
Sarkar B. Reference to: Chen YG, Li AC, Li WY, Huang MY, Li XB, Chen MQ, et al. The feasibility study of a hybrid coplanar arc technique versus hybrid intensity-modulated radiotherapy in treatment of early-stage left-sided breast cancer with simultaneous-integrated boost. J Med Phys 2017;42:1-8. J Med Phys [serial online] 2017 [cited 2019 Jun 19];42:99. Available from: http://www.jmp.org.in/text.asp?2017/42/2/99/208271


Sir,

I must congratulate Chen et al. for their publication. However, I would like to highlight few points on the beam angles used by them in their study. They have described 15° HybridIMRT, 45° HybridIMRT, and HybridVMAT. The tangential wedge pair technique and the field-in-field technique are the most commonly employed techniques in breast irradiation. The advantage of these conventional techniques is the resultant minimum cardiac dose, attributed to its beam arrangement geometry.[1],[2] While choosing the beam/arc angles in any alternative technique, doses to heart, lung, and contralateral breast should be carefully evaluated. Of all these organs, heart is the most vulnerable and rates of major coronary events increased (between 5 and 30 years post radiotherapy) linearly with the mean dose to the heart by 7.4%/Gy with no apparent threshold.[3] The choice of beam angles by Chen et al. other than the 15° HybridIMRT is inappropriate and very high, particularly the 180° VMAT which is not advisable. The mean doses to heart reported by Chen et al. are 8.00 ± 2.61 Gy, 9.58 ± 2.14 Gy, and 7.81 ± 1.60 Gy, respectively, for the 15° HybridIMRT, 45° HybridIMRT, and HybridVMAT techniques.

Instead, if a short tangential arc spanning 30° is used, for a similar prescription dose of 50.4 Gy to the periphery, the reported cardiac dose can be substantially reduced to 3.0 ± 1.0 Gy.[2] Similarly, the ipsilateral lung V20 Gy reported by them in HybridVMAT was 25.49 ± 3.89% which can be significantly reduced to 10.6 ± 5.8% if short tangential arcs are employed. Therefore, it is strongly urged not to use large arc angles or spread out beam angles for breast/chest wall radiotherapy.

Recently, Taylor et. al. done a meta-analysis of 647 randomized control trials published between 2010 and 2015 and reported a mean cardiac dose of 4.4 Gy and whole lung dose of 5.7 Gy.[4] Therefore, irrespective of the technique, cardiac and lung dose reported by Chen et al. is significantly high compared to any modern radiotherapy technique. Therefore, described hybrid techniques should be suitably modified to achieve a mean cardiac dose of <4.5 Gy and 10%-15% of the prescription dose to whole lung before actually used in the clinic.

Financial support and sponsorship

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Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Zhao H, He M, Cheng G, Han D, Wu N, Shi D, et al. A comparative dosimetric study of left sided breast cancer after breast-conserving surgery treated with VMAT and IMRT. Radiat Oncol 2015;10:231.  Back to cited text no. 1
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2.
Giri UK, Sarkar B, Jassal K, Munshi A, Ganesh T, Mohanti B, et al. Left-sided breast radiotherapy after conservative surgery: Comparison of techniques between volumetric modulated arc therapy, forward-planning intensity-modulated radiotherapy and conventional technique. J Radiother Pract 2017;16:101-8.  Back to cited text no. 2
    
3.
Darby SC, Ewertz M, McGale P, Bennet AM, Blom-Goldman U, Brønnum D, et al. Risk of ischemic heart disease in women after radiotherapy for breast cancer. N Engl J Med 2013;368:987-98.  Back to cited text no. 3
    
4.
Taylor C, Correa C, Duane FK, Aznar MC, Anderson SJ, Bergh J, et al. Estimating the risks of breast cancer radiotherapy: Evidence from modern radiation doses to the lungs and heart and from previous randomized trials. J Clin Oncol 2017;35:1641-9.  Back to cited text no. 4
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