Room: AAPM ePoster Library
Purpose: report on the evolution of brachytherapy workflows in the image-based treatments of locally advanced cervical cancer in Canada.
Methods: Physicists in every Canadian province, willing to participate, were emailed a 41-item electronic questionnaire surveying brachytherapy workflow patterns including: fractionation schedules, prescription, equipment, imaging, and treatment delivery.
Results: the n=31 centres contacted, 21 participated in the survey (4 did not respond and 8 offered no brachytherapy). Brachytherapy boost, following external beam treatments (EBRT; 45 Gy in 25 fractions; n = 20), was delivered using high dose rate (HDR; n=20) or pulsed dose rate (PDR; n=1). Intracavitary/insterstitial treatments were done in 9 centres for 25 – 75% of their patients. Operating room availability was 1.75 [1-5] days (median [min-max]) to accommodate 2 [1-3] cervix cases. Imaging modalities used for assisting applicator placement included: US (16), CT (2), and MRI (1). All centres used image-based planning: CT (n=16; with MRI for contouring in n=9), MRI (4), or CBCT (1). For volume-based planning (n=15), contours commonly included Clinical Target Volume (CTV)-High Risk (HR), CTV-Intermediate Risk, rectum, sigmoid, and bladder. The most common HDR dose-fractionation schedule was 7 [4.6 – 10] Gy in 4 [3 – 6] fractions aiming for a total median radiobiological CTV-HR dose (calculated in n=14 centres) of 85 [80 – 95] Gy10. Treatment planning started with standard loading followed by manual/graphical optimization; n=2 used inverse planning. Planning was done either by physicists (n=12) or with assistance from brachytherapy therapists (n=7). Overall treatment times, including EBRT, was 50.5±5.6 days. Currently, no custom applicators (eg. 3D printed) or real-time dose verification during treatment is employed.
Conclusion: to previous studies, there is an increasing trend in the use of image-based volumetric planning, interstitial procedures, and radiobiological dose prescription. Cervical cancer brachytherapy in Canada is becoming more streamlined with use of international practice guidelines.