For the more than 500,000 Americans and Canadians who are diagnosed with unprovoked venous thromboembolism (VTE) each year, VTE may be an early sign of cancer. Despite this, there are no standard practices regarding how aggressively physicians screen for occult cancer among VTE patients.
In a study presented at the International Society on Thrombosis and Haemostasis (ISTH) Congress, Marc Carrier, MD, MSc, reported that the prevalence of occult cancer was low among patients with a first unprovoked VTE and that routine, comprehensive screening with computed tomography (CT) offered no additional detection benefit than a limited screening method.
“It has been described that up to 10 percent of patients with unprovoked VTE are diagnosed with cancer in the year following their VTE diagnosis,” Dr. Carrier, of the University of Ottawa, said during his presentation. “Therefore, it’s appealing for clinicians to screen these patients for occult cancer, but it has led to a lot of great diversity in practices.” For instance, some clinicians prefer to use a limited screening strategy (a history, physical examination, routine blood tests, and a chest X-ray), while others prefer to use additional tests (i.e., CT scans or ultrasound).
In the multicenter, open-label, randomized, controlled SOME (Screening for Occult Malignancy in Patients with Idiopathic Venous Thromboembolism) trial that Dr. Carrier reported on during the meeting, investigators assessed the efficacy of a screening strategy for occult cancer, which included comprehensive CT of the abdomen and pelvis in patients who had a first unprovoked VTE. The study’s findings were simultaneously published in New England Journal of Medicine.
Eight-hundred and fifty-four patients were enrolled from nine Canadian centers. Patients were randomized to undergo conventional limited occult-cancer screening (i.e., basic blood tests, chest radiography, and screening for breast, cervical, and prostate cancer; n=431) or limited occult-cancer screening with combination CT screening (i.e., virtual colonoscopy and gastroscopy, biphasic enhanced CT, parenchymal pancreatogram, and uniphasic enhanced VT of distended bladder; n=423).
The study’s primary endpoint was confirmed cancer that was missed by the screening strategy and detected by the end of the one-year follow-up.
A total of 33 patients (3.9%) had a new diagnosis of cancer at one-year of follow-up: 14 in the limited-screening cohort and 19 in the combination CT screening cohort (p=0.28). In addition, the number of occult cancers missed at one-year follow-up was similar between the two groups, with four (29%) in the limited-screening cohort and five (26%) in the combination CT screening group (p=1.0). See TABLE for further comparisons between the two patient cohorts.
Between the limited-screening and combination CT screening cohorts, there was also no significant difference with regard to detection of:
- early cancers (0.23% vs. 0.71%, respectively; p=0.37)
- overall mortality (1.4% vs. 1.2%, respectively; p>0.99)
- or cancer-related mortality (1.4% vs. 0.95%, respectively; p=0.75)
“The risk of occult cancer in patients with unprovoked or idiopathic VTE was lower than expected,” Dr. Carrier told ASH Clinical News. “Although clinicians need to keep a low index of suspicions for underlying cancer in this patient population, a good history, physical examination, basic blood work, and age- and gender-specific cancer screening seems to be good enough to find most malignancies.”
The study’s open-label design is a limitation, the researchers noted, because it could be associated with a risk of bias regarding the frequency of the outcome, as compared with the frequency that may have been observed in a placebo-controlled trial.
The low incidence of occult cancers is “reassuring for clinicians and patients,” Dr. Carrier added, and will hopefully provide clinicians some answers about how aggressively they should screen for cancer in their VTE patients. “I hope that clinicians will stop doing extensive occult cancer screening for this patient population, as it seems to be potentially associated with more risks (i.e., radiation exposure, additional testing, and complication for false positive findings, anxiety) than benefits.”
Carrier M, Lazo-Langner A, Shivakumar S, et al. Screening for occult cancer in unprovoked venous thromboembolism. N Engl J Med. 2015 Jun 22 [Epub ahead of print].
|Table. Occult Cancer Tumor Types|
|Tumor Type||Limited Occult-Cancer Screening(n=14)||Limited Occult-Cancer Screening plus CT(n=19)|
|Number of tumors/total number|
|During screening period|
|During follow-up period|