Patients with cardiovascular disease who develop major internal bleeding are much more likely to be diagnosed with cancer, a large international clinical trial has found.

Patients with gastrointestinal (GI) bleeding are 18 times more likely to be diagnosed with GI tract cancer, and those who major genitourinary (GU) tract bleeding are 80-fold more likely to be diagnosed with GU cancer, than patients without internal GI or GU bleeding, respectively.

The study results are part of a presentation today at the European Society of Cardiology Congress in Munich, Germany. The clinical trial, called Cardiovascular Outcomes for People Using Anticoagulation Strategies (COMPASS), is led by the Population Health Research Institute (PHRI), a joint institute of McMaster University and Hamilton Health Sciences (HHS).

The COMPASS study involves more than 27,000 patients with coronary or peripheral artery disease in 33 countries.

Previously, COMPASS found that the combination of rivaroxaban combined with aspirin reduces cardiovascular death, stroke or heart attack by 24% compared with aspirin alone. Increased bleeding was an unwanted side effect of the combination of rivaroxaban and aspirin, although there was no significant increase in fatal or critical organ bleeding.

The new analyses demonstrate that patients who developed bleeding were more likely to be diagnosed with cancer, particularly when the bleeding occurred in the GI or GU tracts. One in 5 of all new cancer diagnoses during the trial were in patients who had experienced bleeding.

"This startling insight should stimulate a search for occult cancers in patients with cardiovascular disease who develop bleeding," said John Eikelboom, co-principal investigator of COMPASS, an associate professor of medicine at McMaster's Michael G. DeGroote School of Medicine, and a hematologist at HHS.

Stuart Connolly, co-principal investigator of the COMPASS trial, added: "Bleeding has become a key focus in cardiovascular disease prevention. Most of our efforts have been focused on discovering better ways to prevent and treat bleeding, but if bleeding allows us to diagnose cancer earlier, it may lead to an unexpected benefit."

Connolly is also a professor of medicine at McMaster and a cardiac electrophysiologist at Hamilton Health Sciences.

The trial is sponsored by Bayer AG.