Commissioning and Dosimetric Results of an Indigenously Developed Intra-Vaginal Template for Interstitial Plus Intracavitary High dose Rate Image-Guided Brachytherapy of Advanced Cervix Cancer.

AIM

The goal of this study is to discuss the commissioning and dosimetric parameters achieved during the clinical implementation of an indigenously developed intracavitary (IC) plus interstitial (IS) template for high dose rate (HDR) image-guided brachytherapy (IGBT) in cancer (Ca) cervix. We want to discuss our achieved values of cumulative equi-effective doses (EQD2) for high-risk clinical target volume (HRCTV) and organ at risk (OAR) and compare it with available published results.

MATERIALS AND METHODS

Medanta anterior oblique/lateral oblique template has a total of 19 needles including the central tandem. For commissioning the template with needles, the indigenously made acrylic phantom was used. Oblique and straight needles were placed inside the acrylic phantom and a computed tomography (CT) scan was performed. Sixteen patients were treated in HDR IGBT using this template after external-beam radiotherapy. The IGBT plans were evaluated based on EQD2 of target coverage i.e., dose received by 98% (D_HRCTV), 90% (D_HRCTV), and 50% (D_HRCTV) volume of HRCTV, and dose received by 2 cc (D) and 0.1 cc (D) of OAR using linear quadratic (LQ) radiobiological model.

RESULTS

The autoradiographic in radiochromic film shows that the distance between the needle tip and the middle of the source position is 6 mm. The mean D98%_HRCTV and D90%_HRCTV was 76.8 Gy (range: 70-87.7 Gy, < 0.01) and 84.49 Gy (range: 76.6-96.7 Gy, < 0.01), respectively. Mean EQD2 of D2cc of the bladder, rectum, and sigmoid was 85.6 Gy (range: 77.5-99.6 Gy, < 0.03), 74.3 Gy (range: 70.9-76.7 Gy, < 0.05), and 58.3 Gy (range: 50.6-67.9 Gy, = 0.01), respectively. The mean total reference air kerma at a 1 m distance is 0.489cGy (range: 0.391-0.681cGy).

CONCLUSIONS

The indigenously developed template could attain satisfactory standards in terms of set parameters for commissioning and acceptable dose volume relations in our clinical use for treating the advanced Ca cervix patients who need IC + IS type of HDR IGBT. The comparative analysis with contemporary applicators was acceptable.