Conformal Brachytherapy Planning for Cervical Cancer Using Transabdominal Ultrasound
Received 23 June 2008; received in revised form 28 September 2008; accepted 23 October 2008. published online 27 February 2009.
Purpose
To determine if transabdominal ultrasound (US) can be used for conformal brachytherapy in cervical cancer patients.
Materials and Methods
Seventy-one patients with locoregionally advanced cervix cancer treated with chemoradiation and brachytherapy were included in this study. The protocol consisted of US-assisted tandem insertion and conformal US-based planning. Orthogonal films for applicator reconstruction were also taken. A standard plan was modified to suit the US-based volume and treatment was delivered. The patient then underwent a magnetic resonance imaging (MRI) scan with the applicators in situ. Retrospectively, individual standard (STD), US, and MRI plans were extrapolated for five fractions and superimposed onto the two-dimensional sagittal MRI images for comparison. Doses to Point A, target volume, International Commission on Radiation Units and Measurements (ICRU) 38 bladder and rectal points, and individualized bowel points were calculated on original implant geometry on Plato for each planning method.
Results
STD (high-dose-rate) plans reported higher doses to Point A, target volume, ICRU 38 bladder and rectal points, and individualized bowel point compared with US and MRI plans. There was a statistically significant difference between standard plans and image-based plans—STD vs. US, STD vs. MRI, and STD vs. Final—having consistent (p ≤ 0.001) respectively for target volume, Point A, ICRU 38 bladder, and bowel point. US plan assessed on two-dimensional MRI image was comparable for target volume (p = 0.11), rectal point (p = 0.8), and vaginal mucosa (p = 0.19). Local control was 90%. Late bowel morbidity (G3, G4) was <2%.
Conclusions
Transabdominal ultrasound offers an accurate, quick, accessible, and cost-effective method of conformal brachytherapy planning.
∗Radiation Therapy Services, Peter MacCallum Cancer Center, East Melbourne, Australia
†Division of Radiation Oncology, Peter MacCallum Cancer Center, East Melbourne, Australia
‡Center for Biostatistics and Clinical Trials, Peter MacCallum Cancer Center, East Melbourne, Australia
Reprint requests to: Sylvia van Dyk, Radiation Therapy Services, Peter MacCallum Cancer Center, St. Andrew's Place, East Melbourne 3002, Victoria, Australia. Tel: (61) 396561111; Fax: (61) 396561490
ABSTRACT