The Use of Oblique Needles (Venezia Applicator) in Cervix Cancer Brachytherapy - a Dosimetric Study

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Abstract Summary

Lau TK (1)
(1) Clinical Oncology Department, Pamela Youde Nethersole Eastern Hospital

Introduction:
Brachytherapy is an essential treatment modality for cervical cancer. The rapid BT dose fall-off delivers extremely high dose to the target volume while sparing the nearby organ-at-risk (OAR). The use of hybrid brachytherapy applicator allows both intra-cavitary and interstitial approaches facilitates easy applicator placement with high flexibility of dose distribution. Many hybrid applicators accommodate interstitial needles inserted parallel to the intrauterine tube. The new applicator VeneziaTM contains ovoid holes for both parallel and oblique needles that allow an even higher dose control capability in difficult situations. 

Objectives:
This study evaluates the effectiveness of using oblique needles with VeneziaTM applicator in treating cervical cancer, and attempts to identify tumor characteristics that could benefit from their use.

Methodology:
A total of 20 patients previously treated with 3D planning brachytherapy using hybrid applicator with interstitial needles were recruited retrospectively. The treatment plans that could not achieve the department protocol requirements were selected and replanned with the use of VeneziaTM applicator (virtual plans). For each of such cases one plan was produced with parallel needles insertion only and another plan was produced with both parallel and oblique needles. Dosimetric outcomes of the plans, in particular the D90 of the High Risk CTV (HRCTV) and D2cc of the four OARs: rectum, bladder, sigmoid and small bowel, were analysed and compared to evaluate the improvement brought about by the oblique needles. With 7Gy prescribed to HRCTV D90, the correlation between the volume and maximum radius of HRCTV and OAR D2cc reduction by using oblique needles was also evaluated. A categorical analysis on the plan performance were also carried out.

Results:
35 BT plans were selected in this planning study. With 7Gy prescribed to HRCTV D90, there are significant reduction in D2cc of all the four OARs with the use of oblique needles (p < 0.001). There are also significant correlations between maximum radius of HRCTV and OAR D2cc reduction by having oblique needles (p< 0.001). A maximum HRCTV radius, larger than 34mm, was identify as an indicator of using oblique needles with hybrid applicator.

Conclusion:
Using oblique needles improved BT treatment plan dose compliance and significantly reduced OAR dose. The use of oblique needles should be considered with the maximum HRCTV radius was larger than 34mm.

Abstract ID :
HAC75
Submission Type
HA Staff
Authors (including presenting author) :
Lau TK (1)
Affiliation :
(1) Clinical Oncology Department, Pamela Youde Nethersole Eastern Hospital
Introduction :
Introduction: Brachytherapy (BT) is an essential treatment modality for cervical cancer. The rapid BT dose fall-off delivers extremely high dose to the target volume while sparing the nearby organ-at-risk (OAR). The use of hybrid brachytherapy applicator allows both intra-cavitary and interstitial approaches facilitates easy applicator placement with high flexibility of dose distribution. Many hybrid applicators accommodate interstitial needles inserted parallel to the intrauterine tube. The new applicator VeneziaTM contains ovoid holes for both parallel and oblique needles that allow an even higher dose control capability in difficult situations.
Objectives :
Objectives: This study evaluates the effectiveness of using oblique needles with VeneziaTM applicator in treating cervical cancer, and attempts to identify tumor characteristics that could benefit from their use.
Methodology :
Methodology: A total of 20 patients previously treated with 3D planning brachytherapy using hybrid applicator with interstitial needles were recruited retrospectively. The treatment plans that could not achieve the department protocol requirements were selected and replanned with the use of VeneziaTM applicator (virtual plans). For each of such cases one plan was produced with parallel needles insertion only and another plan was produced with both parallel and oblique needles. Dosimetric outcomes of the plans, in particular the D90 of the High Risk CTV (HRCTV) and D2cc of the four OARs: rectum, bladder, sigmoid and small bowel, were analysed and compared to evaluate the improvement brought about by the oblique needles. With 7Gy prescribed to HRCTV D90, the correlation between the volume and maximum radius of HRCTV and OAR D2cc reduction by using oblique needles was also evaluated. A categorical analysis on the plan performance were also carried out.
Result & Outcome :
Results: 35 BT plans were selected in this planning study. With 7Gy prescribed to HRCTV D90, there are significant reduction in D2cc of all the four OARs with the use of oblique needles (p < 0.001). There are also significant correlations between maximum radius of HRCTV and OAR D2cc reduction by having oblique needles (p< 0.001). A maximum HRCTV radius, larger than 34mm, was identify as an indicator of using oblique needles with hybrid applicator.
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