CT, MRI and ultrasound scanning rates: evaluation of cancer diagnosis, staging and surveillance in Ontario.

Objective: To examine practice patterns and rates of computed tomography (CT), magnetic resonance imaging (MRI), and abdominal ultrasound (AUS) during staging, treatment and surveillance for cancer patients.

Methods: Using Ontario Health Insurance Plan billing data linked to the Ontario Cancer Registry, we determined rates of CT, MRI, and AUS by body site for breast, colorectal, lung, lymphoma, and prostate cancer, from 1998 to 2002. Rates of scans were additionally examined by region of patient residence and time from cancer diagnosis.

Results: The frequency of imaging increased in nearly all scans and tumors over the study period. Rates of peri-diagnosis scans varied substantially by region, ranging from 1.7-fold variation (CT for lung cancer) to 50-fold variation (MRI for breast cancer). For breast cancer, there is possible over-utilization of CT, but overall rates of scanning appear reasonable for the other four cancers.

Conclusions: Considerable regional variation in imaging rates suggests utilization guidelines should be developed or knowledge transfer initiatives are needed to improve compliance to existing guidelines. In breast cancer, there appears to be over-utilization of imaging. Further studies are necessary to determine utilization for each stage, the reason scans were obtained, and the impact of scans on patient outcomes.