Venous Clots Common in Young Sarcoma Patients

BALTIMORE, April 23 -- Venous blood clots, although frequently asymptomatic, are nonetheless common in children and young adults with sarcoma, researchers here found.

In 122 consecutive sarcoma patients diagnosed and treated at the National Cancer Institute, 19 (16%) had a total of 23 thromboembolic events, according to Ido Paz-Priel, M.D., of Johns Hopkins, and colleagues.

Of the 23 events, 46% were detected only incidentally, they reported in the April 20 issue of the Journal of Clinical Oncology.

The finding suggested that children and young adults with sarcomas "should be monitored carefully for the development of thromboembolic events and suggestive symptoms should be pursued aggressively," the researchers said.

Sarcoma, like most cancer, is conducive to thrombosis because tumor cells promote coagulation and secrete cytokines that trigger inflammation, the researchers noted. Other factors, such as chemotherapy, surgery, immobilization, and having a central venous access device, can also increase the risk of blood clots.

But the risk of thrombosis in children and young adults with sarcoma was not known, so the researchers analyzed records of consecutive patients diagnosed and treated from October 1980 through July 2002.only at NCI's Pediatric Oncology Branch.

Of the 122 patients for whom data were available, 61 had Ewing's sarcoma, 20 had osteosarcoma, 26 had rhabdomyosarcoma, and the rest had other sarcomas.

The rate of thromboembolism was similar for each type - 10% for osteosarcoma, 13% for Ewing's sarcoma, 15% for rhabdomyosarcoma, and 33% for the other forms combined.

The study also found:

• 53% of patients with a venous clot had it on presentation.
• 43% of the emboli were in the deep veins of the extremities, 22% were pulmonary, and 17% in the inferior vena cava.
• 35% of the emboli were associated with tumor compression.
• 13% were associated with venous catheters.

The researchers said the study suggests that patients with metastatic disease are more likely to have thromboembolic events, although the difference did not reach statistical significance.

Emboli developed in 23% of patients with metastatic disease at presentation, compared to 10% of those with localized disease. The odds ratio was 2.59, with a 95% confidence interval from 0.9 to 7.1, which almost reached statistical significance, at P<0.06.

Because the awareness of thrombosis has increased over time, the researchers compared the prevalence of events before and after 1993. More patients presented with metastatic disease before the cutoff than after - 44% versus 34%, a difference that was significant at P<0.02.

However, the researchers found, only 7% of the early patients were diagnosed with an thromboembolic event, compared with 23% in the most recent period, a difference that was significant at P<0.015.

The differences are "likely to due to improved imaging and increased index of suspicion," the researchers said.

One implication of that fact, they added, is that the current data "likely underestimate the true magnitude of this problem."

Such clotting events are important because "thromboembolism is a potentially life-threatening complication that is almost always amenable to therapy," according to co-author Alan Wayne, M.D., clinical director of the Pediatric Oncology Branch.

Few patients in the study underwent comprehensive evaluation for prothrombotic disorders and information regarding genetic or acquired risk factors was not available for most patients.