9. Comparison between conventional simulator planning and conformal 3-D planning for cervical cancer teletherapy

Abstract

The using of simulator planning based on bony landmarks for pelvic irradiation of cervix cancer is associated with a risk in a geographical miss, which may be generated by inadequate knowledge of the individual anatomy. 3D treatment planning system let us know an individual topography of pelvic organs, enables to mark a PTV and it allows more adequate coverage.

Purpose

The aim of this study was to evaluate a benefit resulting from 3D treatment planning for teletherapy of cervical cancer.

Material and method

In our study on 15 patients with cervical carcinoma in the stage IIIB simulator planning of, box” technique was performed. Next we defined the PTV in 3D-planning system and compared the dose distribution, obtained with both methods, in the target volumes and organs at risk using dose-volume histograms.

Results

In 4 of 15 patients the encompassment of the PTV by the treated volume was inadequate in case of simulator planning. The treated volumes based on 3D-planning were 8% smaller than volumes based on simulator planning. The treated volume/planning target volume ratio was 1,64 for simulator planning and 1,50 for 3D planning. 3D-planning system resulted in a reduction of the irradiated bladder volume (−12%) and the bowel volume (−9%). The bladder and bowel volumes in treated volumes depended on bladder fillings.

Conclusions

Implementation of 3D treatment planning system in teletherapy of cervical cancer helps to avoid a geographical miss, to reduce both the treated volume and the doses delivered to organs at risk.