A prospective comparison of computerized-tomography (CT) based with trans-rectal-ultrasonography (TRUS) assistance and magnetic-resonance imaging (MRI) based target-volume definition during image guided adaptive brachytherapy for cervical cancers

Publication date: Available online 7 June 2018
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Umesh Mahantshetty, Pushpa Naga CH, Chira Ranjan Khadanga, Shivakumar Gudi, Supriya Chopra, Lavanya Gurram, Swamidas Jamema, Yogesh Ghadi, Shyamkishore Shrivastava
PurposeAlthough magnetic resonance imaging (MRI) represents the gold standard for image guided adaptive brachytherapy (IGABT) for cervical cancer, majority of brachytherapy (BT) continues to be guided by computerized tomography (CT). However, CT seems to overestimate the target volume definition while the potential of trans-rectal ultrasonography (TRUS) needs further evaluation. With an aim to evaluate CT-based target contouring with incorporation of TRUS during BT, we conducted this prospective comparative study.Materials and methodsPatients with locally advanced cervical cancer undergoing MR IGABT between January 2013 and March 2014 were included. During BT procedure, TRUS imaging with central tandem in situ was acquired at three representative levels. Reference points/dimensions (D1 to D4) of hypo-echoic region seen on TRUS images with respect to central tandem were recorded. CT and MR BT planning imaging was performed after BT application. High risk clinical target volume (HR-CTV) was contoured on CT with incorporation of clinical and TRUS imaging findings and compared with gold standard MR based target approach.ResultsImage sets belonging to 25 patients [FIGO IIB:11 (44%) and IIIB: 14 (56%)] were evaluable. The mean (±SD) volume of HR-CTV on CT and MR imaging were 39.1 (±20) cm³ and 39 (±19) cm³ respectively (r=0.92, p<0.001).Significant correlation was found between HR-CTV dimensions (width and thickness) between CT and MR at various levels (r=0.70 to 0.80, p<0.001).In addition, absolute differences in target dimensions between CT and MR were less than 0.5 cm. Also a strong correlation was seen for patients with medial and lateral parametrial invasion (p<0.05) between CT and MR imaging as compared to no parametrial disease at BT. Furthermore, the mean differences of HR-CTV width between CT and MR contours at various levels, irrespective of parametrial involvement was 0.1- 0.4 cm only.ConclusionsOur study suggests, CT based target and OAR delineation utilizing MR at diagnosis and real time TRUS information during BT seems comparable to the gold standard MR based approach in IGABT for cervical cancers.

Teaser

Target volume definition and delineation (high risk) at the time of brachytherapy (BT) is an important step in image guided adaptive brachytherapy for cervical cancers. We present the first prospective study comparing CT-based target delineation with incorporation of trans-rectal ultrasonography at BT and gold standard approach of MR-based target delineation and report comparable results. These findings have a potential impact on brachytherapy practice for cervical cancers across the globe.


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