Blood clots in leg veins (deep vein thrombosis) or lung arteries (pulmonary embolism) that happen for no reason (i.e. unexplained) are both called "unprovoked venous thromboembolism" (VTE). These unexplained blood clots can be the first symptom of cancer. Up to 10% of patients with unexplained blood clots will be diagnosed with cancer within one year of their blood clot diagnosis.

These cancers can be found anywhere in the body although the relationship appears stronger with the pancreas, ovary and liver. Cancer testing in patients with blood clots is controversial. There is presently a wide variety of expert opinions and practices. Previous studies showed that a limited cancer screen including a medical history, physical examination, basic blood work and chest X-ray, will find about 90% of cancers. More recent and better designed studies showed that the limited cancer screen misses many cancers and needs to be improved. More extensive cancer testing may find more cancers but is potentially uncomfortable for patients, costs a lot of money and involves a lot of people.

The "comprehensive computed tomography" is less uncomfortable, inexpensive, radiological test made to find many cancers at once. Thus, the scientific question to be asked is: Does a "comprehensive computed tomography" miss less cancers than a limited cancer screen in patients with blood clots?

The main goal of this study is to find out if a "comprehensive computed tomography" misses less cancers than a limited cancer screen in patients with unexplained blood clots.

The second goal of the study is 1) to find out if a "comprehensive computed tomography" finds more "curable" cancers than the limited cancer screen; 2) to find out if the patients diagnosed with cancer are still alive and cancer-free after one year (i.e. the patients with curable cancer were treated and are doing well); 3) to prove that a negative "comprehensive computed tomography" means that the patient will not have cancer and; 4) to find out if a "comprehensive computed tomography" is well tolerated and safe for patients.

Inclusion Criteria:

• Patients with a new diagnosis of unprovoked proximal deep vein thrombosis (DVT) or pulmonary embolism (PE) will be eligible to participate into the study:

  • Unprovoked VTE is defined as the absence of any of the following predisposing factors:

    1. known active cancer;
    2. recent (less than 3 months) paralysis, paresis or plaster immobilization of the lower extremities;
    3. recently bedridden for period of 3 or more days, or major surgery, within the previous 12 weeks requiring general or regional anaesthesia;
    4. previous unprovoked VTE;
    5. known thrombophilia (hereditary or acquired)

  • Proximal DVT is defined as a non-compressibility of any vein segment from the common femoral vein to the trifurcation of the popliteal vein or a persistent intra-luminal filling defect of the iliac, common femoral, superficial femoral or popliteal veins on contrast venography.

  • Pulmonary embolism is defined as:

    1. patients with a high/intermediate pre-test probability (Wells' model > 4) + high probability V/Q scan;
    2. positive pulmonary angiogram; or
    3. spiral CT demonstrating intraluminal filling defect in a vessel larger than a segmental artery

Exclusion Criteria:

Patients will be excluded from the study if they have any of the following criteria:

• Age < 18 years-old;
• Refusal or inability to provide informed consent;
• Greater than 21 days post diagnosis of idiopathic VTE
• Index VTE event of UEDVT or unusual site DVT
• Diagnosis of SSPE in the absence of above or below knee DVT
• Allergy to contrast media;
• Creatinine clearance < 60 ml/min;
• Claustrophobia or agoraphobia;
• Weight > 130 kg;
• Diagnosis of ulcerative colitis; and
• Diagnosis of glaucoma
• Current pregnancy