CT Screening for Occult Cancer ‘Exceedingly Unlikely’ to Benefit Unprovoked VTE Patients
Computed tomography screening for occult malignancy is not effective in patients with idiopathic venous thromboembolism
- Date: 24 Jun 2015
- Author: Lynda Williams, Senior medwireNews Reporter
- Topic: Imaging, Diagnosis and Staging
medwireNews: Computed tomography (CT) imaging for occult malignancy is unnecessary for patients with a first unprovoked venous thromboembolism (VTE), suggest the results of a randomised, open-label trial.
Just 3.9% of 854 patients had a new diagnosis of occult cancer within a year of an idiopathic VTE event and this rate did not significantly differ between patients assigned to undergo a basic screening strategy for malignancy alone or alongside abdomen and pelvis CT, at 3.2% versus 4.5%.
“Our results suggest that a limited screening strategy for occult cancer (history taking, physical examination, basic blood testing, chest radiography, and age-specific and sex-specific cancer screening) may be adequate for patients who have a first unprovoked venous thromboembolism”, say Marc Carrier, from Ottawa Hospital Research Institute in Ontario, Canada, and co-workers.
The team reports in The New England Journal of Medicine that four (29%) of 14 occult cancers diagnosed within a year of VTE were missed by the basic screening protocol, as were five (26%) of 19 occult cancers in the patients who also received abdominal and pelvis CT.
The absolute 1-year rate of biopsy-proven occult cancer in patients with unprovoked VTE and negative screening tests was a comparable 0.93% for the limited screening group and 1.18% for those who also received CT imaging.
And there was no significant difference between the screening and screening plus CT groups with regard to the average time to a cancer diagnosis (4.2 vs 4.0 months) or the rate of detection of early malignancy (0.23 vs 0.71%). The rate of cancer mortality was also similar in the two groups (1.4 vs 0.9%).
The researchers explain that the absolute difference between the two screening strategies was just 0.25 percentage points and that even in a best-case scenario of 1.12 percentage points, using the lower boundary of the confidence interval, the number needed to screen would be 91 patients for each missed occult tumour.
Noting that a radiation-induced cancer is estimated to occur in around one in 460 women and one in 498 men given abdominal and pelvis CT, the team concludes: “Hence, it is exceedingly unlikely that CT permits early detection of clinically relevant number of cancers and even less likely that early detection of these cancers would provide an overall net clinical benefit.”
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