Dosimetric Comparison between Conventional 2D and 3D Conformal Radiotherapy in the Treatment of Intact Breast Cancer
Radiotherapy (RT)
techniques after Conservative Breast Surgery (CBS) vary. Three Dimension (3D)
planning allows for better plan optimization compared to 2 Dimension (2D) plans
and also allowsfor creating Dose Volume Histograms (DVHs) for both Planning
Target Volume (PTV) and Organs at Risk (OAR). The aim of this study was
to compare dosimetrically between 3D treatment planning using MIT and 2 methods
of 2D treatment planning for patients with breast cancer that underwent
conservative surgery with respect to PTV coverage of the breast and the SCV lymph node, hot spot in the junctional area
and dose to OAR.
Twenty consecutive patients with CBS planned for whole breast and
supraclavicular (SCV) RT at the National Cancer Institute (NCI), Egypt between
January and June 2016 were included in this study. All patients were planned
clinically in 2D fashion with no more than 2 cm of ipsilateral lung allowed in
the tangential fields “Limited 2D” (Limit-2D) then Target and OAR volumes were
drawn according to the Radiation Therapy Oncology Group (RTOG) guidelines and
3D plans and a central slice PTV-based 2D plan, “Modified 2D” (Mod-2D), were
performed in the same Computerized Tomography (CT) slices for each patient.
Mono-Iso-Centeric technique (MIT) was used in 3D plans. DVH parameters were
used to compare the three plans.
In 3D plans, compared to Limit-2D, coverage improved for the intact
breast (V95% = 95% versus (Vs) 69%, p = 0.036) and SCVPTV (V90% = 90% Vs 65%, p
= 0.01). The breast and SCV V107%, V112% and Dmax were better with 3D plan, but
not statistical significant (NS). Junctional hot spots were 120% and 107% in
the Limit-2D and 3D plans respectively (p = 0.04). The dose to the heart, mean
(333 Vs 491 cGy), V10 (5% Vs 10%) and V20 (3% Vs 7%), Ipsilateral lung V20 (19%
Vs 26%), and contra lateral breast D-max (205 Vs 462 cGy) were higher in 3D
plans but NS, and the dose to the cord was the same. Comparison between 3D and
Mod-2D showed better OAR sparing with 3D with mean heart dose (491 cGy Vs 782
cGy, p = 0.025) and Ipsilateral lung V20 (26% Vs 32%, p = 0.07% with
statistically comparable target coverage.
This study demonstrated that application of 3D plan using MIT improved
coverage of breast and SCVPTVs with minimizing hot spot at the junctional area
if compared with Limit-2D plans with comparable dose to OAR. When compared with
Mod-2D plans, 3D plans not only had better target coverage but also better
sparing of OAR, the latter was statistically significant.
Article
by Amr Amin, et al, from Egypt.
Full
access: http://mrw.so/dkuqR
Image
by T KONI, from Flickr-cc.
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