Venous thromboembolism (VTE) can be the first sign of an occult cancer, but aggressive cancer screening is not worthwhile in individuals who present with a VTE, conclude researchers reporting a new meta-analysis.
The meta-analysis examined individual data for more than 2000 patients with unprovoked VTE and found that using an extensive screening strategy detected more cancer cases at an initial screening compared with a more limited approach.
Overall, occult cancer was detected in 1 in 20 patients within a year of diagnosis with an unprovoked VTE, and older age was associated with a higher cancer prevalence.
But while an extensive screening strategy identified more cases initially, it did not translate to higher detection of early-stage cancer. In a comparison of the two types of strategies, the proportion of early-stage cases did not differ.
Importantly, note the authors, the benefit of an extensive screening strategy remains unclear as to whether the increase in cancer detection “will translate into benefits with regard to important patient outcomes, such as lower morbidity and mortality.”
The study is published online August 21 in Annals of Internal Medicine.
“Despite the substantial increase in cancer detection with extensive screening, not enough evidence exists yet to support the routine use of these tests in patients with unprovoked VTE,” the authors conclude.
In an accompanying editorial, Geno Merli, MD, and Howard Weitz, MD, both from Thomas Jefferson University Hospital, Philadelphia, Pennsylvania, agree with the study authors.
Although the current analysis showed that an extensive strategy might initially detect more cancers than a limited one, whether outcomes are improved remains unclear, they note.
“It supports the opinion that for most patients, history; physical examination; basic laboratory studies; and age-, sex-, and risk factor–specific tests comprise the initial cancer screening after the diagnosis of unprovoked VTE,” Dr Merli and Dr Weitz write. “We believe that extensive screening is not cost-effective and that further study is needed to better define the effect of advanced imaging in patients older than 50 years.”
Finding the Best Approach
The meta-analysis was conducted by Marc Carrier, MD, from the Ottawa Hospital Research Institute, University of Ottawa, Ontario, Canada, and colleagues. They combined patient-level data from 10 recently published prospective studies of occult cancer screening for a total cohort of 2316 patients with unprovoked VTE.
The authors defined limited screening as a combination of interventions that included medical history taking, physical examination, basic blood tests, chest radiography, and age- and/or sex-specific tests (such as mammography).
Extensive screening strategies differed and were heterogeneous across the studies but generally included advanced imaging modalities, such as computed tomography (CT) and ultrasonography of the abdomen or whole-body positron emission tomography–CT.
In 7 studies (n = 2001) that enrolled patients before screening, 101 individuals were diagnosed with cancer during the first 12 months (pooled period prevalence of 5.2%). The most commonly diagnosed malignancy was colon cancer (17%), followed by cancers of the lung (15%) and pancreas (11%).
Screening strategies were compared directly in 3 studies (n = 885 with limited screening and n = 945 with extensive screening). Within this group, the 12-month period prevalence of cancer was 4.2% for the limited screening group and 5.6% among patients who had undergone extensive screening.
Occult cancer was detected at screening in 21 of 885 patients (2.4%; 3 studies) who underwent a limited screening strategy vs 50 of 1116 (4.5%; 7 studies) who underwent extensive screening.
Extensive screening was associated with a 2-fold higher probability of detecting occult cancer (adjusted odds ratio, 2.0; P = .012; 3 studies) at initial screening compared with limited screening. However, the difference in the proportion of early-stage solid cancers between the two approaches was not statistically significant (P = .30).
A total of 54 cancer cases were detected by a limited screening strategy. Of those, 16 (30%) were stage 0, I, or II solid cancer; 31 (57%) were stage III or IV solid cancer; and 7 (13%) were hematologic malignancies.
For extensive screening, 17 cases were detected, of which 8 (47%) were stage 0, I, or II solid cancer; 7 (41%) were stage III or IV solid cancer; and 1 (5.9%) was a hematologic malignancy. Stage could not be determined in 1 patient (5.9%).
However, age was a risk factor; cancer prevalence increased linearly with advancing age and was 7-fold higher in those aged 50 years and older than in younger patients (6.8% vs 1.0%; P < .001).
There was no outside funding source for the study. Several of the authors have disclosed relationships with industry, as noted in the paper. The editorialists have disclosed no relevant financial relationships.
Ann Intern Med. Published online August 22, 2017. Abstract, Editorial
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