Sporadic rather than frequent scanning linked to CT-induced cancers
MedWire News: Study findings suggest that the majority of CT-induced cancers occur in patients undergoing sporadic rather than frequent scanning, raising the challenge of changing attitudes towards medical uncertainty.
"Currently, it is very difficult for a physician to advise any one patient with acute symptoms that the patient should not undergo a CT examination, and forgo its potential for immediate diagnosis or reassurance, because of the tiny and possibly only theoretical risk for cancer 20 years or more later," say Robert Zondervan (Massachusetts General Hospital, Boston, USA) and co-authors.
The researchers identified 25,104 patients aged 18-35 years who underwent chest or abdominopelvic CT scans between 2003 and 2007 and categorized the total number of scans per body part as scanned rarely (<5 times), intermediately (5-15 times), or frequently (>15 times). Cumulative radiation exposure was used to estimate cancer risk.
In total, 95% of patients overall, 93.8% of patients undergoing chest CT, and 95.7% of patients undergoing abdominopelvic CT were rarely scanned, compared with 0.3%, 0.4%, and 0.2%, respectively, who were frequently scanned.
Among the 36 patients who were frequently scanned with chest CT, the most common diagnoses were cancer (52.8%), lung transplantation for cystic fibrosis (30.6%), and leukemia or lymphoma with bone marrow transplantation (16.6%). The most common diagnosis among the 34 frequently scanned abdominopelvic CT patients was also cancer (73.5%).
Sarcoma was the most common diagnosis in the cancer follow-up category, representing 19% of chest CT and 30% of abdominopelvic CT patients. The most common indication for chest and abdominopelvic CT examinations was cancer follow-up (57.7% and 54.9%, respectively).
Over an average 5.4-years follow-up, 46% of frequently scanned patients died of complications linked to pre-existing underlying disease, before radiation-induced cancer could potentially influence their health.
When the authors calculated predicted cancer incidence and mortality linked to CT scanning, they found that of the 47 cancers predicted in the entire cohort, 36 (77%) were expected in the rarely scanned group, and just two (3%) in the frequently scanned group.
"Whatever risk is associated with radiation exposure, efforts to reduce CT scanning of the many patients scanned rarely, rather than of the few scanned frequently, has the greatest potential to reduce population exposure to medical radiation," write the authors in the Journal of the American College of Radiology.
The team calls for enhancements in medical education concerning appropriate utilization of radiologic examinations to help reduce the number of young adults undergoing unnecessary CT examinations.
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By Ingrid Grasmo