Marianne S Assenholt1, Anne Vestergaard2, Jesper F Kallehauge2, Sandy Mohamed3, Søren K Nielsen2, Jørgen B Petersen2, Lars Fokdal3, Jacob C Lindegaard3, Kari Tanderup4. 1. Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark. Electronic address: mariasse@rm.dk. 2. Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark. 3. Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. 4. Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark; Department of Oncology, Aarhus University Hospital, Aarhus, Denmark; Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.
Abstract
PURPOSE: To describe a new technique involving high-precision stereotactic intensity-modulated radiation therapy (IMRT) boost in combination with intracavitary-interstitial (IC-IS) brachytherapy (BT) in cervical tumors that cannot be sufficiently covered by IC-IS-BT due to extensive residual disease and/or difficult topography at the time of BT. METHODS AND MATERIALS: Three patients with stage IIIB-IVA cervical cancer had significant residual disease at the time of BT. MRI-guided IC-IS-BT (pulsed-dose rate) was combined with a stereotactic IMRT boost guided according to the BT applicator in situ, using cone beam CT. The planning aim dose (total external beam radiotherapy and BT) for the high-risk clinical target volume (HR-CTV) was D90 >70-85 Gy, whereas constraints for organs at risk were D2cm3 <70 Gy for rectum, sigmoid, and bowel and <90 Gy for bladder in terms of equivalent total dose in 2 Gy fractions. An IMRT boost adapted to the BT dose distribution was optimized to target the regions poorly covered by BT. RESULTS: HR-CTV doses of D90 >81 Gy were obtained in the central HR-CTV and D90 >69 Gy in the distal regions of HR-CTV. Image-guided set up of the IMRT boost with the applicator in situ was feasible. The dose plans were robust to intra-fraction uncertainties of 3 mm. Local control with acceptable morbidity was obtained at a followup of 3, 2.5, and 1 year, respectively. CONCLUSIONS: The combination of MRI-guided BT with an applicator-guided stereotactic IMRT boost is feasible. This technique seems to be useful in the few cases where HR-CTV coverage cannot be obtained even with IS-IC-BT.
PURPOSE: To describe a new technique involving high-precision stereotactic intensity-modulated radiation therapy (IMRT) boost in combination with intracavitary-interstitial (IC-IS) brachytherapy (BT) in cervical tumors that cannot be sufficiently covered by IC-IS-BT due to extensive residual disease and/or difficult topography at the time of BT. METHODS AND MATERIALS: Three patients with stage IIIB-IVA cervical cancer had significant residual disease at the time of BT. MRI-guided IC-IS-BT (pulsed-dose rate) was combined with a stereotactic IMRT boost guided according to the BT applicator in situ, using cone beam CT. The planning aim dose (total external beam radiotherapy and BT) for the high-risk clinical target volume (HR-CTV) was D90 >70-85 Gy, whereas constraints for organs at risk were D2cm3 <70 Gy for rectum, sigmoid, and bowel and <90 Gy for bladder in terms of equivalent total dose in 2 Gy fractions. An IMRT boost adapted to the BT dose distribution was optimized to target the regions poorly covered by BT. RESULTS: HR-CTV doses of D90 >81 Gy were obtained in the central HR-CTV and D90 >69 Gy in the distal regions of HR-CTV. Image-guided set up of the IMRT boost with the applicator in situ was feasible. The dose plans were robust to intra-fraction uncertainties of 3 mm. Local control with acceptable morbidity was obtained at a followup of 3, 2.5, and 1 year, respectively. CONCLUSIONS: The combination of MRI-guided BT with an applicator-guided stereotactic IMRT boost is feasible. This technique seems to be useful in the few cases where HR-CTV coverage cannot be obtained even with IS-IC-BT.