Grant: Project Grant

Blood clots in leg veins (deep vein thrombosis) or lung arteries (pulmonary embolism) that happen for no reason are both called "unprovoked venous thromboembolism" . These unexplained blood clots can be the first manifestation of cancer. Current data suggest that after the occurrence of a first unexplained blood clot, approximately 5% of the patients will be diagnosed with cancer in the following year. In patients older than 50, this rate reaches 7%. Unfortunately, all types of cancers can be found and whether systematic cancer screening should be performed has remained controversial: extensive cancer testing may find more cancers but is potentially uncomfortable and harmful for patients. Markedly, two recent studies demonstrated that the number or cancer diagnosed or missed after an extensive screening approach was not different to the numbers observed after a limited screening approach (medical history, physical examination, basic blood work and chest X-ray). However, focusing workup in patients older than 50 could greatly improve the performance of extending cancer screening strategies. A PET scan, is a non-invasive whole body imaging test performed to find out many cancers at once. It combines computed tomography (CT) with functional imaging using sugar. It is routinely used for the diagnosis, staging and restaging of various cancers in oncology. Previous studies showed promising performances in finding an unknown cancer at the time of an unexplained blood clot by using PET scan. Our research question is whether a PET scan misses less cancers than a limited cancer screening plan in patients aged 50 years or more who are diagnosed with a first unexplained blood clot. We hope our study will also help in identifying more curable cancers when PET scan is performed and that a negative PET scan means that the patient has a risk of subsequent cancer similar to the general population.