Survey of Image-guided Radiation Therapy use in the United States

Abstract

Image-guided radiation therapy (IGRT) is a novel array of techniques that utilize modern imaging modalities for target delineation, tumor localization, and patient set-up. The prevalence of IGRT use among U.S. radiation oncologists is unknown. A random sample of 1600 radiation oncologists belonging to the American Society of Radiation Oncology was surveyed by email and fax between February 1st, 2009 and March 31st, 2009 regarding frequency of IGRT use, clinical applications, and future plans for use. The definition of IGRT included any sophisticated imaging for target delineation used during planning or any in-room imaging used for set-up or tumor localization during treatment. Of the 1089 evaluable participants, 379 (35%) responded. 511 potential participants were excluded, because they were either retired or uncontactable. Of responders, 65% were in private practice (PP) and 35% were academic (AC). The proportion that used IGRT for target delineation was 95% (PP, 95%; AC, 96%). The most commonly used techniques were FDG-PET (76%), MRI (72%), and 4D-CT (44%). 4D-CT use was more common among academics (67% vs 30%, p < 0.001) than private practitioners. Less commonly used techniques included functional MRI (fMRI) (9%), MR spectroscopy (7%), SPECT (8%), and other PET tracers (3%). Among those using IGRT for target delineation, the most common disease sites treated were lung (78%), head and neck (H&N) (75%), and CNS (74%). The majority of responders using target delineation techniques used them in <25% of their patients. The proportion that used IGRT for in-room set-up/tumor localization was 94% (PP, 94%; AC, 94%). The percentage using ultrasound, video, planar modalities (EPID, kV gantry-mounted imaging, etc.) and volumetric modalities (CBCT, CT-on-rails, etc.) were 23%, 3%, 80% and 59%, respectively. CBCT use was more common among academics (64% vs 45%, p < 0.001) than private practitioners. Among those using IGRT for in-room setup/tumor localization, the most common disease sites treated were prostate (85%), H&N (70%), CNS (67%), and lung (63%). For prostate cancer, the most commonly used modalities were EPID with fiducials (44%) and CBCT (44%), while 25% of responders reported having ceased use of ultrasound. For lung cancer, the most commonly used modalities were EPID without fiducials (48%) and CBCT (47%). The majority of responders using in-room IGRT used them in ≤50% of their patients. 66% and 60% planned to increase use of IGRT for target delineation and in-room set-up/tumor localization, respectively. No current users planned to decrease or cease use of IGRT. IGRT is widely used among radiation oncologists in the US for both target delineation and treatment delivery. Based on prospective plans of responders, the frequency of use is expected to increase.