Photo by Angela Mary Butler
TORONTO—A CT scan of the abdomen and pelvis does not improve cancer detection in people with unexplained venous thromboembolism (VTE), results of the SOME trial suggest.
“Unexplained blood clots have long been thought of as a possible early warning sign of cancer, with previous studies suggesting that up to 10% of patients with unexplained clots will be diagnosed with cancer within the year,” said Marc Carrier, MD, of Ottawa Hospital Research Institute in Ontario, Canada.
“Some clinical guidelines recommend a CT scan of the abdomen and pelvis in these patients, in addition to other cancer screening, but there has been very little evidence to know if the added CT scan is helpful. We did this study to find out.”
Dr Carrier and his colleagues described this research in an article published in NEJM and in a presentation given at the 2015 ISTH Congress (abstract LB001*).
The trial involved 854 patients treated at 9 Canadian centers who had an unexplained VTE—deep vein thrombosis, pulmonary embolism, or both.
The patients were randomized to receive basic cancer screening or basic cancer screening plus a CT scan of the abdomen and pelvis. Basic cancer screening included blood work and a chest X-ray, in addition to gender-specific screening (such as a breast exam, Pap smear, and prostate exam) if it had not been conducted in the last year.
Overall, 33 patients (3.9%) had a new diagnosis of occult cancer during the 1-year follow-up period.
There was no significant difference in the rate of diagnosis between the patients who received only basic screening and the patients who underwent CT as well—3.2% (14/431) and 4.5% (19/423), respectively (P=0.28).
Likewise, there was no significant difference in the number of cancers that were not diagnosed by the screening strategies. Basic screening failed to uncover 4 cancers (29%), and basic screening plus CT failed to reveal 5 cancers (26%, P=1.0).
In addition, there was no significant difference between the screening strategies in the time to cancer diagnosis or cancer-related mortality. The mean time to cancer diagnosis was 4.2 months in the basic screening group and 4.0 months in the CT group (P=0.88). And the rate of cancer-related mortality was 1.4% and 0.9%, respectively (P=0.75).
“Although it is tempting to believe that more cancer screening is always better, our study shows that this is not necessarily the case,” Dr Carrier said. “And in fact, unnecessary CT scanning has real risks. It can cause stress and anxiety in patients, as well as radiation exposure, and it can lead to over-investigation of false-positive findings. Our study means many patients will now be able to avoid this.”
That could lead to significant savings for the healthcare system, according to the researchers. For example, approximately 30,000 Canadians suffer from an unexplained VTE every year, and a CT scan costs approximately $300. So avoiding unnecessary CT scans could result in a potential saving of $9 million per year in Canada alone.
*Information in the abstract differs from that presented at the meeting.