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

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.”

Reference

Carrier M, Lazo-Langner A, Shivakumar S, et al. Screening for occult cancer in unprovoked venous thromboembolism. N Engl J Med 2015; Advance online publication 22 June. DOI: 10.1056/NEJMoa1506623

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