Understanding the problem

Many people are diagnosed with DVT or PE that is unexplained (no obvious reason why it happened). For most people, the cause will remain a mystery. However, cancer is known to cause blood clots in some people, and about 4 out of 100 people with unexplained DVT or PE will have cancer without knowing they have it.

Cancer Care Ontario recommends tests to check for cancer in everyone depending on their sex and age. These tests are called cancer screening tests. For example, women over age 50 are advised to have a mammogram to check for breast cancer every 2 years, and men and women over age 50 are advised to have a test for blood in the stool every 2 years to check for bowel cancer. (**These are just examples, and the guidelines differ for people with a personal or strong family history of cancer.)

Researchers asked if, in addition to the routine cancer screening tests, doctors should arrange for a CT scan (special type of x-ray) of the abdomen and pelvis for everyone who has an unexplained DVT or PE. If CT scans find more cancers at an early stage, they may be more treatable, and therefore finding them could save lives. However, some cancers do not require treatment in the early stages, and finding them can lead to unnecessary, potentially harmful tests (e.g., biopsy) and increased anxiety for patients.  Also, CT scans require use of a radioactive dye which can cause allergic reactions and serious kidney problems in some patients.