Dosimetric comparison of MRI-based HDR brachytherapy and stereotactic radiotherapy in patients with advanced cervical cancer: A virtual brachytherapy study.

AIM: To evaluate the treatment plans of 3D image-guided brachytherapy (BT) and stereotactic robotic radiotherapy with online image guidance - CyberKnife (CK) in patients with locally advanced cervix cancer. METHODS AND MATERIALS: Ten pairs of plans for patients with locally advanced inoperable cervical cancer were created using MR based 3D brachytherapy and stereotaxis CK. The dose that covers 98% of the target volume (HR CTV D98) was taken as a reference and other parameters were compared. RESULTS: Of the ten studied cases, the dose from D100 GTV was comparable for both devices, on average, the BT GTV D90 was 10-20% higher than for CK. The HR CTV D90 was higher for CK with an average difference of 10-20%, but only fifteen percent of HR CTV (the peripheral part) received a higher dose from CK, while 85% of the target volume received higher doses from BT. We found a significant organ-sparing effect of CK compared to brachytherapy (20-30% lower doses in 0.1 cm(3), 1 cm(3), and 2 cm(3)). CONCLUSION: BT remains to be the best method for dose escalation. Due to the significant organ-sparing effect of CK, patients that are not candidates for BT could benefit from stereotaxis more than from classical external beam radiotherapy.