Comparative analysis of radiation exposure from CT scan and VQ scan in the diagnosis of pulmonary embolism: an early-onset cancer risk assessment

Background — Computed tomography pulmonary angiography (CTPA) and ventilation-perfusion (VQ) scans are used to diagnose pulmonary embolism (PE), but there are concerns about ionizing radiation exposure from CTPA and its potential to increase cancer risk.

Objectives — This study compared early-onset cancer risk between patients diagnosed with PE who underwent CTPA or VQ imaging.

Methods — We conducted a retrospective population-based matched cohort study using linked clinical and administrative health databases in Ontario, Canada. Patients aged 18–75 years diagnosed with PE between 2004 and 2021 were included. Each patient who underwent VQ scan was matched by age and sex to a patient who underwent CTPA. Using a landmark statistical framework starting at 18-months post PE diagnosis, cancer diagnoses were identified using the Ontario Cancer Registry. Cox proportional hazards regression models assessed the association between imaging modality and cancer risk.

Results — A total of 20,476 patients were included, 10,238 in each cohort. The median follow-up was 5.26 years for patients in the CTPA group and 6.96 years for those in the VQ group. The overall cancer rate was 10.96 per 1,000 person-years (95% CI: 10.42–11.52). There was no significant difference in cancer risk between the CTPA (10.93 per 1,000 person-years, 95% CI: 10.14–11.78) and VQ scan groups (10.98 per 1,000 person-years, 95% CI: 10.26–11.75; p=0.93). Multivariable analysis demonstrated no significant association (HR 0.95; 95% CI: 0.86–1.05).

Conclusions — In this population-based cohort, cancer risk associated with exposure to CTPA was not significantly higher than that associated with VQ lung scans.