Estimation of dose-volume parameters of female urethra as organ-at-risk during interstitial brachytherapy in gynecological malignancies

Abstract Background The aim of the study was to dosimetrically compare multicatheter interstitial brachytherapy (MIBT) and stereotactic radiotherapy with CyberKnife (CK) for accelerated partial breast irradiation (APBI) especially concerning the dose of organs at risk (OAR-s). Patients and methods Treatment plans of thirty-two MIBT and CK patients were compared. The OAR-s included ipsilateral non-target and contralateral breast, ipsilateral and contralateral lung, skin, ribs, and heart for left-sided cases. The fractionation was identical (4 x 6.25 Gy) in both treatment groups. The relative volumes (e.g. V100, V90) receiving a given relative dose (100%, 90%), and the relative doses (e.g. D0.1cm3, D1cm3) delivered to the most exposed small volumes (0.1 cm3, 1 cm3) were calculated from dose-volume histograms. All dose values were related to the prescribed dose (25 Gy). Results Regarding non-target breast CK performed slightly better than MIBT (V100: 0.7% vs. 1.6%, V50: 10.5% vs. 12.9%). The mean dose of the ipsilateral lung was the same for both techniques (4.9%), but doses irradiated to volume of 1 cm3 were lower with MIBT (36.1% vs. 45.4%). Protection of skin and rib was better with MIBT. There were no significant differences between the dose-volume parameters of the heart, but with MIBT, slightly larger volumes were irradiated by 5% dose (V5: 29.9% vs. 21.2%). Contralateral breast and lung received a somewhat higher dose with MIBT (D1cm3: 2.6% vs. 1.8% and 3.6% vs. 2.5%). Conclusions The target volume can be properly irradiated by both techniques with similar dose distributions and high dose conformity. Regarding the dose to the non-target breast, heart, and contralateral organs the CK was superior, but the nearby organs (skin, ribs, ipsilateral lung) received less dose with MIBT. The observed dosimetric differences were small but significant in a few parameters at the examined patient number. More studies are needed to explore whether these dosimetric findings have clinical significance.

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Implementation of 3D-CT based brachytherapy in the postoperative radiotherapy of cervical cancer: Treatment technique and dose-volume parameters

Acta chirurgica iugoslavica ◽

10.2298/aci0904201p ◽

2009 ◽

Vol 56 (4) ◽

pp. 201-207

Author(s):

V. Plesinac-Karapandzic ◽

N. Borojevic ◽

B. Markovic ◽

V. Stankovic ◽

S. Vuckovic ◽

...

Keyword(s):

Cervical Cancer ◽

At Risk ◽

Cancer Treatment ◽

Postoperative Radiotherapy ◽

Reference Points ◽

Intracavitary Brachytherapy ◽

Treatment Technique ◽

3D Ct ◽

Dose Volume ◽

Organ At Risk

Intracavitary brachytherapy has an important roll in developing complications in postoperative radiotherapy of cervical cancer. 3D-CT based brachytherapy gives precisely estimating doses to organ at risk. In this study, we show our preliminary results in implementation of 3D-imaging based postoperative brachytherapy of cervical cancer: treatment technique and dose-volume parameters. During 2009 year, in 6 patients with early stage I-II of cervical cancer, brachytherapy treatment planning was based on the radiographs and CT imaging brachytherapy technique. Mean values of ICRU reference points of rectum was R max 4,2Gy and bladder B max. 4,5Gy, while estimated volume-dose parameters D0.1 cm 3 D1.0 cm 3 D2.0 cm 3 were presented with higher dose. Volume of organ at risk reflected the need for better bladder preparation. Our initial experience in performing CT-based brachytherapy, enabled us to introduce the characteristics of the parameters, assessment of their significance from the aspect of mutual relations applicators and organs at risk. Further analysis are needed, for monitoring the effects of 3D planning on complications.

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