CT screen ineffective for detecting cancer in patients with blood clots [SOME Trial]

1. There was no clinical benefit from the addition of CT imaging to a cancer screening strategy for patients with a first unprovoked venous thromboembolism.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Clotting in the context of injury and bleeding is a natural and essential process. However, clots that form within blood vessels can cause significant issues. Certain medical conditions can upset the balance of the blood clotting system, and make the formation of abnormal blood clots more likely. Cancer is one condition that produces a hypercoagulable state. The diagnosis of an abnormal clot without an apparent cause could be an early sign of cancer. However, there is currently no consensus on the best strategy for cancer screening in these patients.

The Screening for Occult Malignancy in Patients with Idiopathic Venous Thromboembolism (SOME) trial compared two strategies of cancer screening: one with CT imaging of the abdomen and pelvis, and another without. About 4% of the 854 patients in the study were diagnosed with cancer within a year. Both screening strategies were equivalent in their performance; they both missed about 25-30% of cancers.

The study results suggest that a basic screen consisting of a clinical exam, blood tests, a chest x-ray and age- and sex-specific cancer screening is sufficient for a patient with a first unprovoked venous blood clot.

Click to read the online first article, published today in NEJM

Click to read an accompanying editorial in NEJM

Relevant Reading: Is extensive screening for cancer in idiopathic venous thromboembolism warranted?

In-Depth [randomized controlled trial]: This multi-center trial from Canada randomized 854 patients with a new diagnosis of unprovoked symptomatic venous thromboembolism (pulmonary embolism or deep-vein thrombosis) to two screening strategies. The limited strategy involved a clinical evaluation with history-taking and physical exam, some basic blood tests (complete blood count, serum electrolyte and creatinine levels, liver function tests) and a chest radiograph. The other group received the same limited strategy as well as a CT of the abdomen and pelvis.

There were 4 “undetected” cancers in the limited-screening group and 5 in the CT group. However, these cancers diagnosed after the screening may be new, and unrelated to the VTE. In fact, the 12-month incidence of cancer among those who were negative after the limited screening was similar to the incidence of cancer among people without a history of VTE. This suggested that the limited screening was able to detect essentially all the occult malignancies, and malignancies that developed in the subsequent year are simply what would be expected among the general population.

The CT strategy did not produce any clinical benefit in this study. It did not improve the detection of occult malignancy, nor did it reduce the time to diagnosis or cancer mortality.

Image: PD

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