Blood and Clots Series: My patient has a pulmonary embolism. Should I screen them for cancer?

In Blood & Clots, Medical Concepts by Eric TsengLeave a Comment

All the content from the Blood & Clots series can be found here.

CanMEDS Roles addressed: Expert, Leader

Case Description

An 83 year old female presents for follow-up after completing 3 months of oral anticoagulant therapy with Rivaroxaban for her unprovoked deep vein thrombosis. She did some research online and heard about a link between venous thrombosis and cancer, and asks why you are not getting a CT scan to rule out malignancy. Should you screen her for cancer? If so, which tests are necessary?

What is the association between unprovoked venous thromboembolism and occult malignancy?

25-40% of all VTE events are unprovoked, and 5-10% of unprovoked VTE are associated with underlying occult (undiagnosed) cancer 1 2 3 . In those diagnosed with cancer after VTE, most cancer diagnoses occur within one year of diagnosing VTE 3 4. This association raises the question: Should  we screen patients for cancer upon diagnosing unprovoked VTE? Should we screen them extensively using a strategy incorporating “screening” CT scans? Or should we limit our approach to routine/limited strategy (history, physical exam, basic bloodwork, and age-appropriate cancer screening)?

Should I be screening my patients with unprovoked VTE extensively for occult cancer?

There have been randomized trials and meta-analyses performed to try and answer this question.

  • In the largest RCT addressing this issue, the SOME study (n = 854), patients with first unprovoked VTE were randomized to extensive screening (comprehensive CT scans) versus limited screening. There was no difference in the number missed occult cancer diagnoses at 1 year, suggesting that extended screening is not universally warranted 3. These results are consistent with other studies 5.
  • While these individual trials have shown no difference in the detection of occult cancer, a recent meta-analysis pooling individual data from randomized trials suggests that extensive strategies may detect more cancer cases initially, despite there being no difference at 12 months after VTE diagnosis. It is unclear whether this translates to improved patient outcomes 6.

This is kind of confusing. How do I put this all together?

There are limited data suggesting that extensive screening may increase the detection of occult cancer. However, keep in mind that

    1. The overall incidence of occult cancer after unprovoked VTE is still low (5%)
    2. It’s unclear whether finding occult cancer earlier actually makes any differences to clinical outcomes (cancer-related survival, overall survival)
    3. Unnecessary CT scans may result in harm – radiation and contrast exposure, patient anxiety, downstream unnecessary tests 5

At the moment there isn’t enough evidence to support extensive cancer screening in everyone. At minimum, your patients should undergo age-appropriate cancer screening. Do have a high index of suspicion for cancer in these patients and consider more extensive screening in those with unexplained symptoms potentially attributable to cancer (unintentional weight loss, iron deficiency, cytopenias, especially in older patients) 7.


STOP! Think about how you would advise and counsel your patient at this point. Then, click here to see the case resolution.

You discuss the above considerations with your patient and she decides against pursuing any CT scans as she has been feeling well and she was reassured by her normal labwork and unconcerning history and physical exam. She continues Rivaroxaban for extended secondary VTE prevention. You ask her primary care provider to ensure her cancer screening is up to date within the next 12 months. On a routine mammogram four months later a breast lump is found and she is diagnosed with breast cancer.


Main Messages

  • Extensive cancer screening with CT scans after unprovoked VTE is not recommended in all patients, as it likely does not significantly increase the rate of occult cancer detection and has not been shown to impact clinical outcomes.
  • Maintain a high index of suspicion; routine cancer screening should be recommended, with targeted extensive screening in selected patients.
  • As extensive cancer screening remains controversial, it does not need to be considered in the ED in patients with unprovoked VTE. However, close follow up by a primary care provider or hematologist is important.

All the content from the Blood & Clots series can be found here.

This post was reviewed by Jesse Leontowicz, Brent Thoma and copyedited by Rebecca Dang.


Heit J, Spencer F, White R. The epidemiology of venous thromboembolism. J Thromb Thrombolysis. 2016;41(1):3-14. [PubMed]
Carrier M, Le G, Wells P, Fergusson D, Ramsay T, Rodger M. Systematic review: the Trousseau syndrome revisited: should we screen extensively for cancer in patients with venous thromboembolism? Ann Intern Med. 2008;149(5):323-333. [PubMed]
Carrier M, Lazo-Langner A, Shivakumar S, et al. Screening for Occult Cancer in Unprovoked Venous Thromboembolism. N Engl J Med. 2015;373(8):697-704. [PubMed]
White R, Chew H, Zhou H, et al. Incidence of venous thromboembolism in the year before the diagnosis of cancer in 528,693 adults. Arch Intern Med. 2005;165(15):1782-1787. [PubMed]
Khan F, Vaillancourt C, Carrier M. Should we screen extensively for cancer after unprovoked venous thrombosis? BMJ. 2017;356:j1081. [PubMed]
van E, Le G, Otten H, et al. Screening for Occult Cancer in Patients With Unprovoked Venous Thromboembolism: A Systematic Review and Meta-analysis of Individual Patient Data. Ann Intern Med. 2017;167(6):410-417. [PubMed]
Ihaddadene R, Corsi D, Lazo-Langner A, et al. Risk factors predictive of occult cancer detection in patients with unprovoked venous thromboembolism. Blood. 2016;127(16):2035-2037. [PubMed]

Eric Tseng

Dr. Eric Tseng is a hematologist who works at St. Michael’s Hospital and the University of Toronto. His clinical practice is focused on non-cancer hematology and thrombosis medicine. His academic interests are in postgraduate medical education and competency based education.