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Brachytherapy. 2014 Jul-Aug;13(4):361-8. doi: 10.1016/j.brachy.2014.02.003. Epub 2014 Mar 18.

Proof of principle: Applicator-guided stereotactic IMRT boost in combination with 3D MRI-based brachytherapy in locally advanced cervical cancer.

Author information

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.

KEYWORDS:

Applicator-guidance; Brachytherapy; Cervical cancer; IMRT boost; MRI-guidance

PMID:
24656732
DOI:
10.1016/j.brachy.2014.02.003
[Indexed for MEDLINE]

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