3-T MRI-based adaptive brachytherapy for cervix cancer: treatment technique and initial clinical outcomes.
OBJECTIVE
To report the techniques and initial clinical outcomes for MRI-based adaptive brachytherapy (MRIB-ABT) using 3-T MRI.


METHODS
All patients who underwent MRIB-ABT between January 2008 and June 2012 for cervical cancer using 3-T MRI for at least three fractions were retrospectively reviewed. The institutional standard for initiation of brachytherapy planning was 100% of dose at point A and 160% at the vaginal surface with five fractions of 500-550 cGy at Point A. The dose distribution was modified to enhance coverage of the high-risk clinical target volume (HR-CTV) and to spare the organs at risk (OAR) by altering dose specification distances around the tandem and the percentage of the Point A dose around the ring or ovoids.


RESULTS
Eighteen patients (FIGO stages IB = 4, II = 12, III = 1, and IVA = 1) underwent eighty-two 3-T MRI-based insertions. All patients received 3D conformal, external beam radiation (45-50.4 Gy). The median gross tumor volume pretreatment was 38 cm(3) (2-165 cm(3)) compared with 4.8 cm(3) (1-9 cm(3)) at the first high-dose rate fraction with a median volume reduction of 88%. Dose specification at the level of Point A was altered in 51% of 3-T MRI fractions from the standard 20 mm (range, 14-18 mm) and in 8% at the ring surface to optimally cover the HR-CTV and spare the OAR. The 2-year local control, disease-specific survival, and overall survival are 100%, 100%, and 93%, respectively.


CONCLUSIONS
MRIB-ABT using 3-T MRI for treatment of cervix cancer allows for customized alterations in dose specification that minimize dose to the OAR and maximize coverage of the HR-CTV.
Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI.
Jordan
J
Kharofa
Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI.
Natalya
N
Morrow
Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI.
Tracy
T
Kelly
Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI.
Jason
J
Rownd
Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI.
Eric
E
Paulson
Department of Gynecologic Oncology, Medical College of Wisconsin, Milwaukee, WI.
Janet
J
Rader
Department of Gynecologic Oncology, Medical College of Wisconsin, Milwaukee, WI.
Denise
D
Uyar
Department of Gynecologic Oncology, Medical College of Wisconsin, Milwaukee, WI.
William
W
Bradley
Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI. Electronic address: berickson@mcw.edu.
Beth
B
Erickson
D000230:Adenocarcinoma / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000379:methods*; D002294:Carcinoma, Squamous Cell / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009367:Neoplasm Staging; D058958:Organs at Risk; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000379:methods*; D012189:Retrospective Studies; D016019:Survival Analysis; D016896:Treatment Outcome; D047368:Tumor Burden; D002583:Uterine Cervical Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*
3-T MRI; Cervical cancer; MRI-based brachytherapy