Over 68 million CT scans are performed annually in the United States. The numbers of these scans are increasing with clinicians casting wider diagnostic nets and with patients requesting (and paying for) broader preventative and prophylactic imaging.
A new study has documented that patients with high cumulative radiation exposure levels, from multiple CT exams over their lifetime, are at a significant increased risk for cancer. The investigators, Sodickson A. et al., reported that cumulative CT radiation exposure adds to baseline cancer risks. These findings were published this month in the Journal of Radiology, authored by Sodickson’s group out of the prestigious Brigham and Woman’s Hospital in Boston.
Lifetime CT Exposure Study Methods
The study methods were as follows:
A group of 31,462 patients were studied via examination of medical records.
A total of 190,712 CT scans over a period of 22 years was documented in the group.
A per patient cumulative CT radiation exposure total was calculated by adding all CT doses received to date utilizing a typical amount of radiation per type of CT study.
The Biological Effects of Ionizing Radiation VII method (BEIR) was used to estimate Lifetime Attributable Risk (LAR), accounting for sex and age at the time of exposure as well.
Patients with an LAR greater than 1% were stratified using billing ICD9 codes and electronic order entry information.
Patient Scan And Radiation Data In CT And Cancer Risk Study
33% of patients studied had five or more CT scans in lifetime
5% of patients studied had experienced 22 to 132 scans
15% received cumulative effective (lifetime to study date) doses of more than 100mSv
4% received between 250 to 1375 mSV cumulative doses
CT Scan And Cancer Study Results
Science Daily reported that the lead investigator, Aaron Sodickson, M.D., stated that “most patients accrued small cumulative cancer risks”.
7.3 % of patients had enough recurrent CT scans to raise their estimated cancer risk by 1% or more (above baseline levels in the United States).
315 patients in the study, that were in the top percentage of this group, had an increased risk of 2.7 to 12%.