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A blood clot in an abdominal vein-i.e., splanchnic venous thrombosis (SVT), known to be relatively rare-may be an indicator of undiagnosed cancer, according to research now available online in Blood ( The findings also suggest that such clots also predict shorter survival in patients with liver and pancreatic cancers.

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As explained in a news release from the journal, it has been known that compared with the general population, individuals who develop deep-vein thrombosis (DVT) or pulmonary embolism (PE) are two to four times more likely to be diagnosed with cancer within the next year. In the presence of cancer, blood typically clots more easily, and expanding tumors may compress a vein in its path, reducing or minimizing blood flow. In other cases, surgery, inflammation, or tumor growth can injure blood vessels, promoting clotting.


For the study, researchers analyzed the medical-discharge diagnoses of 1,191 Danish patients diagnosed with SVT from 1994 to 2011, following the records for a median of 1.6 years, calculating the risk of a subsequent cancer diagnosis compared with the expected risk in the general population in Denmark. Researchers also assessed the survival outlook of patients with SVT as compared with cancer patients without blood clots.


"As we learn more about the association between many types of thromboses and cancer, we also want to better understand these more rare clots and how they can perhaps signal a hidden cancer," said the study's lead author, Kirstine K. Sogaard, MD, of Aarhus University Hospital. "In this case, we had access to comprehensive data that we believed could provide insights useful to clinicians caring for patients with this condition."


After linking the SVT patient records to the Danish Cancer Registry, the researchers found that 183 of the 1,191 patients were later diagnosed with cancer, and more than half were identified within three months of the SVT diagnosis. The majority of these cancers occurred in the liver, pancreas, or blood.


After comparing the cancer incidence among SVT patients with national Danish cancer rates, the investigators estimated that patients with SVT were 33 times more likely to be diagnosed with cancer than expected during the first three months following SVT diagnosis.


Seeking to understand how SVT might affect survival in those patients with cancer, the team then compared the survival in these patients with a matched cohort of cancer patients without the blood clots. While patients with liver or pancreatic cancer had a poor outcome whether they did or did not have SVT, those with SVT and these cancers did have a markedly worse three-month survival-44 percent versus 55 percent for patients with liver cancer, and 33 percent versus 53 percent for patients with pancreatic cancer.


There was no significant difference in survival between blood cancer patients with and without SVT, but there was a higher incidence of myeloproliferative neoplasms beyond 12 months following SVT diagnosis, potentially indicating delayed diagnosis, the team wrote.


"This study is the first to demonstrate in a large population that patients who develop splanchnic venous thrombosis are likely to be diagnosed with cancer within a relatively short time period," Sogaard said. "As we continue to learn more about patients who suffer from these blood clots, it will be important to examine the pros and cons of screening for these hidden cancers."