February 09, 2016
2 min read

Unprovoked VTE may increase risk for subsequent cancer diagnosis

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Unprovoked venous thromboembolism appeared associated with a consistently high risk for subsequent cancer diagnosis, according to results of a population-based cohort study.

The risk for cancer appeared greatest in the first 6 months after VTE.

Individuals with cancer account for 20% of all patients diagnosed with VTE, and 15% of those with cancer will develop clinically detectable VTE, according to study background.

Chia-Hung Kao, MD, of Graduate Institute of Clinical Medical Science at China Medical University in Taiwan, and colleagues used Taiwan National Health Insurance program claims data from 1998 to 2008 to investigate the relationship between unprovoked VTE and subsequent risk for cancer.

Kao and colleagues identified 27,751 patients (median age, 61.8 years; 51.3% women) with unprovoked VTE. Researchers matched them 4:1 to 110,409 people (median age, 61.6 years; 51.3% women) without unprovoked VTE. Study participants were matched according to age, sex and index year.

Median follow-up was 4.18 years (range, 0.003-13) in the VTE group and 5.87 years (range, .003-13) in the non-VTE group.

Patients with unprovoked VTE demonstrated double the risk for cancer compared with those who did not have unprovoked VTE (adjusted HR [aHR] = 2.26; 95% CI, 2.16-2.37).

Risk for cancer among patients with VTE appeared higher among those aged 20 to 34 years (aHR = 5.61; 95% CI, 3.91-8.05) than those aged 65 years or older (aHR = 1.82; 95% CI, 1.71-1.93).

Overall risk for cancer appeared higher in the VTE group when follow-up was less than 6 months (aHR = 15.2; 95% CI, 13.7-16.9) than when follow-up was more than 3 years (aHR = 1.11; 95% CI, 1.02-1.2).

The highest sex- and age-specific cancer incidence rates in the VTE group occurred among patients aged 65 years or older (men, aHR = 3.59; 95% CI, 3.37-3.84; women, aHR = 2.45; 95% CI, 2.28-2.63). However, age-specific adjusted HR was highest among those in the younger age group and declined with older age (P < .001 for all).

At 6 months follow-up, the most prevalent primary tumors in the VTE group were lung cancer (aHR = 2.82, 95% CI, 2.51-3.16), colorectum cancer (aHR = 1.73, 95% CI, 1.52-1.97), liver cancer (aHR = 1.87, 95% CI, 1.64-2.13), hematologic malignancies (aHR = 3.61, 95% CI, 2.99-4.36) and other types of cancer (aHR = 2.58, 95% CI, 2.18-3.05).

Among those with less than 6 months follow-up, patients in the VTE group demonstrated greater risk for all cancer types than those without VTE. However, among patients with more than 3 years of follow-up, those with VTE only demonstrated greater risk for lung cancer (aHR = 1.33; 95% CI, 1.08-1.65).

Patients in the VTE group with cancer appeared more than twice as likely to die within 1 year than study participants in the non-VTE group who developed cancer (adjusted OR = 2.18; 95% CI, 1.98-2.4).) This supports previous research that showed unfavorable prognoses for subsequent malignancy after the diagnosis of unprovoked venous thromboembolism, Kao and colleagues wrote.

The potential for surveillance bias may limit these findings, researchers wrote. Also, because the Taiwan National Health Insurance program database does not include lifestyle information, researchers could not account for smoking, alcohol consumption or other behaviors that could affect health.

“[This] study provides evidence that higher risks of overall and site-specific cancer exist among patients with unprovoked VTE,” Kao and colleagues wrote. “This phenomenon is more evident for patients with 1 year of follow-up following diagnosis of unprovoked VTE. Moreover, unfavorable outcomes were observed among the cancer patients following unprovoked VTE, and aggressive screening programs for occult cancer in patients with unprovoked VTE might yield no clinical benefit.” – by Kristie L. Kahl

Disclosure: The researchers report no relevant financial disclosures.