When a patient develops a blood clot in the Deep Venous system or in the blood vessels of the lung, the clot needs to be thinned out with blood thinners so that it doesn’t grow, break off and migrate. The patient also needs to be evaluated whether there was a cause for the blood clot. The pathways of management and length of anticoagulation or “blood thinning” are different for Provoked or Unprovoked Clots.
Transient risk factors e.g., trauma, surgery, prolonged immobility, or pregnancy or delivery, long distance travel via airplanes, etc., can “provoke:” a clot. When no risk factors are identified, the clot is considered unprovoked.
Known cancer can provoke a clot; when a clot is unprovoked, a search for Occult, or hidden, or as yet undeclared cancer is recommended. Meta-analyses of older studies have shown up to 10% of patients with unprovoked clots receive a diagnosis of cancer within the year after their diagnosis of a venous clot. More than 60% of occult cancers are diagnosed shortly after the diagnosis of unprovoked venous thromboembolism. After that, the incidence rate of cancer diagnosis gradually declined and returned to the rate in the general population after 1 year. These previous studies have led to routine screening for Occult Cancers with an unprovoked clot.
How much screening is needed?
A new study published in the New England Journal of Medicine examines the question.
Patients were divided into limited screening (blood work/ Chest XRay and mammogram/ pelvic exam/ colonoscopy by standard guidelines) versus all this + CT scans.
This study showed that Patients with unprovoked venous thromboembolism and a negative screening result for occult cancer with the limited screening strategy had a low incidence of cancer diagnosis of 0.93% (95% CI, 0.36 to 2.36) over the following year, which is no different than the incidence reported in patients without venous thromboembolism. The addition of routine CT scans did not increase Occult Cancer detection rates, or improve outcomes. In addition CT scans incur radiation exposure..
Because the prevalence of occult cancer was low among patients who had a first unprovoked venous thromboembolism and routine screening with CT of the abdomen and pelvis did not provide a clinically significant benefit, these should be practice changing findings. In addition, patients with unprovoked clots need not sit in fear of an occult malignancy, but will need to do routine testing and screening procedues.
Screening for Occult Cancer in Unprovoked Venous Thromboembolism
Marc Carrier, M.D., et al.
June 22, 2015DOI: 10.1056/NEJMoa1506623