MAGNETIC RESONANCE IMAGING-GUIDED INTRACAVITARY BRACHYTHERAPY FOR CANCER OF THE CERVIX

Purpose: To determine the feasibility and benefits of optimized magnetic resonance imaging (MRI)-guided brachytherapy (BT) for cancer of the cervix. Methods and Materials: A total of 20 patients with International Federation of Gynecology and Obstetrics Stage IB-IV cervical cancer had an M RI-compatible intrauterine BT applicator inserted after external beam radiotherapy. MRI scans were acquired, and the gross tumor volume at diagnosis and at BT, the high-risk (HR) and intermediate-risk clinical target volume (CTV), and rectal, sigmoid, and bladder walls were delineated. Pulsed-dose-rate BT was planned and delivered in a conventional manner. Optimized MRI-based plans were developed and compared with the conventional plans. Results: The HR CTV and intermediate-risk CTV were adequately treated (the percentage of volume treated to >= 100% of the intended dose was >95%) in 70% and 85% of the patients with the conventional plans, respectively, and in 75% and 95% of the patients with the optimized plans, respectively. The minimal dose to the contiguous 2 cm 3 of the rectal, sigmoid, and bladder wall volume was 16 +/- 6.2, 25 +/- 8.7, and 31 +/- 9.2 Gy, respectively. With MRI-guided BT optimization, it was possible to maintain coverage of the HR-CTV and reduce the dose to the normal tissues, especially in patients with small tumors at BT. In these patients, the HR percentage of volume treated to >= 100% of the intended dose approached 100% in all cases, and the minimal dose to the contiguous 2-cm(3) of the rectum, sigmoid, and bladder was 12-32% less than with conventional BT planning. Conclusion: MRI-based BT for cervical cancer has the potential to optimize primary tumor dosimetry and reduce the dose to critical normal tissues, particularly in patients with small tumors. (C) 2009 Elsevier Inc.