TORONTO (FRONTLINE MEDICAL NEWS) – The prevalence of occult cancer is low in patients with a first unprovoked venous thromboembolism, according to results from a multicenter, randomized study presented at the International Society on Thrombosis and Haemostasis congress.

In addition, routine screening with the addition of a comprehensive CT scan of the abdomen and pelvis was no better than routine screening alone in detecting occult cancer in this population.

Those are key findings that Dr. Marc Carrier of the University of Ottawa presented from the Screening for Occult Malignancy in Patients with Idiopathic Venous Thromboembolism (SOME) trial, a multicenter, open-label, randomized controlled trial that compared the efficacy of conventional screening with or without comprehensive CT of the abdomen/pelvis for detecting occult cancers in patients with unprovoked venous thromboembolism (VTE). The results of this study were published the same day as his presentation in the New England Journal of Medicine.

“It has been described that up to 10% of patients with unprovoked VTE are diagnosed with cancer in the year following their VTE diagnosis,” Dr. Carrier said. “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. Some clinicians prefer to use a limited screening strategy that would include a history, physical examination, routine blood tests, and a chest X-ray. Other clinicians prefer to use the limited screening strategy in combination with additional tests. That could be CT of the abdomen and pelvis, ultrasound, or tumor marker, or [computed axial tomography] scan. It’s hard for a physician to know what to use.”

For the SOME trial, a total of 854 patients with unprovoked VTE were randomized to two groups: 431 to limited occult cancer screening (basic blood work, chest X-ray, and breast/cervical/prostate cancer screening) and 423 to limited screening in combination with a comprehensive CT of the abdomen/pelvis. The comprehensive CT included a virtual colonoscopy and gastroscopy, a biphasic enhanced CT, a parenchymal pancreatogram, and a uniphasic enhanced CT of distended bladder. The primary outcome was confirmed cancer that was missed by the screening strategy and detected by the end of the 1-year follow-up period.

Dr. Carrier reported that 33 patients (3.9%) had a new diagnosis of cancer in the interval between randomization and 1-year follow-up: 14 in the limited-screening group and 19 in the limited-screening-plus-CT group, a difference that was not statistically significant (P = .28). In addition, the number of occult cancers missed by the end of the 1-year follow-up period was similar between the two groups: four in the limited-screening group and five in the limited-screening-plus-CT group.

He and his associates also found no significant differences between the limited-screening group and the limited-screening-plus-CT group in the rate of detection of early cancers (0.23% vs. 0.71%, respectively; P = .37), in overall mortality (1.4% vs. 1.2%; P > 0.99), or in cancer-related mortality (1.4% vs. 0.95%; P = .75).

“Occult cancers are not nearly as common as we thought they were, which is reassuring for clinicians and patients because then we don’t have to do a lot of investigations to try and find them, and often scare patients and expose them to radiation and additional procedures,” Dr. Carrier said in an interview. “Limited screening alone, which is what is recommended in Canada and in the United States for age- and gender-specific screening, is more than reasonable for these patients.”

The SOME trial was funded by the Heart and Stroke Foundation of Canada. Dr. Carrier had no relevant financial conflicts to disclose.

Therese Borden contributed to this article.