eISSN: 2081-2841
ISSN: 1689-832X
Journal of Contemporary Brachytherapy
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1/2021
vol. 13
 
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abstract:
Original paper

Venezia applicator with oblique needles improves clinical target volume coverage in distal parametrial tumor residue compared to parallel needles only

Manon Kissel
1
,
Nathalie Fournier-Bidoz
2
,
Olivier Henry
2
,
Sophie Bockel
1
,
Tamizhanban Kumar
1
,
Sophie Espenel
1
,
Cyrus Chargari
1

1.
Radiation Therapy Department, Gustave Roussy, Villejuif, France
2.
Medical Physics Department, Gustave Roussy, Villejuif, France
J Contemp Brachytherapy 2021; 13, 1: 24–31
Online publish date: 2021/02/18
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Introduction
Residual distal parametrial involvement after radiochemotherapy is a true challenge for brachytherapists since the width and asymmetry of high-risk clinical target volume (HR-CTV) are difficult to cover properly with a standard implant.

Material and methods
Dosimetric plans of five patients treated with Venezia advanced gynecological applicator at our institution were reviewed. For each patient, we compared the original plan with a new plan where oblique needles were removed and re-optimized manually. Optimization process was halted when EQD210 D90 HR-CTV reached 90 Gy, when one hard constraint to organs at risk (OARs) was reached according to the EMBRACE II protocol, or when dose-rate of one of OARs exceeded 0.6 Gy/h.

Results
Tumors were large; median HR-CTV volume was 64 cc and median distance between tandem and outer contour of HR-CTV was 40 mm. For the five patients, HR-CTV EQD210 D90 was superior in the plan using oblique needles, with a median difference of 6.5 Gy (range, 1.7-8.5 Gy). Median D90 HR-CTV and intermediate-risk CTV (IR-CTV) were significantly increased with oblique needles: 85.9 Gy (range, 83.2-90.3 Gy) vs. 81.5 Gy (range, 77.4-84 Gy), and 68.7 Gy (range, 66.3-72.3 Gy) vs. 67 Gy (range, 64.3-69.1 Gy), p = 0.006 for both. There were no significant differences in the dose to OARs. Plans with only parallel needles had less favorable dose distribution, with cold spots on the outer parametria and higher vaginal activation to compensate parametrial coverage in its inferior part.

Conclusions
VeneziaTM applicator permits reproducible application to increase CTV coverage in patients with distal parametrial tumor residue during brachytherapy, while maintaining acceptable dose to OARs.

keywords:

brachytherapy, cervix cancer, interstitial, parametrium, Venezia, applicator

 
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