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. 2016 Jan 25;8(1):e467.
doi: 10.7759/cureus.467.

Intensity-Modulated Radiation Therapy Versus 3D Conformal Radiotherapy for Postoperative Gynecologic Cancer: Are They Covering the Same Planning Target Volume?

Jelena Lukovic  1 , Nikhilesh Patil  2 , David D'souza  1 , Barbara Millman  3 , Brian P Yaremko  1 , Eric Leung  4 , Frances Whiston  5 , George Hajdok  3 , Eugene Wong  6
Affiliations

Intensity-Modulated Radiation Therapy Versus 3D Conformal Radiotherapy for Postoperative Gynecologic Cancer: Are They Covering the Same Planning Target Volume?

Jelena Lukovic et al. Cureus. .

Abstract

Background and purpose: This study compares dosimetric parameters of planning target volume (PTV) coverage and organs at risk (OAR) sparing when postoperative radiotherapy for gynecologic cancers is delivered using volumetric modulated arc therapy (VMAT) versus a four-field (4FLD) box technique.

Material and methods: From July to December 2012, women requiring postoperative radiation for gynecologic cancers were treated with a standardized VMAT protocol. Two sets of optimized 4FLD plans were retrospectively generated: one based on standard anatomical borders (4FLD) and one based on the clinical target volume (CTV) created for VMAT with a 2 cm expansion guiding field border placement (4FLD+2). Ninety-five percent isodose curves were generated to evaluate PTV coverage.

Results: VMAT significantly improved dose conformity compared with 4FLD and 4FLD+2 plans (p < 0.001) and provided additional coverage of the PTV posteriorly and superiorly, corresponding to coverage of the presacral and proximal iliac vessels. There was a significant reduction in dose to all OARs with VMAT, including a 58% reduction in the volume of the small bowel receiving more than 45 Gy (p=0.005).

Conclusions: Despite treating a larger volume, radiotherapy using a 4FLD technique is less homogenous and provides inferior coverage of the PTV compared with VMAT. With meticulous treatment planning and delivery, VMAT effectively encompasses the PTV and minimizes dose to OARs.

Keywords: cervix cancer; dosimetry; endometrial cancer; gynecological cancers; intensity-modulated radiotherapy (imrt).

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Comparative dose distributions for A) 4FLD+2, B) 4FLD, and C) VMAT.
Figure 2
Figure 2. PTV coverage with a 4FLD plan generated based on standard anatomic borders. Undercovered areas are posterior (purple) and superior (yellow).
See this image and copyright information in PMC

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