Research conducted by United States scientists has revealed that the Avastin cancer drug increased the risk of developing blood clots in the veins by a third when combined with chemotherapy, the mainstay treatment for cancer patients.

A study involving 15 clinical trials and almost 8,000 people showed that the popular Avastin, which is marketed by Roche and Genentech, rendered the risk of blood clots in the veins to go up from approximately 10 percent of cancer patients to nearly 13 percent of them.

Dr. Shenhong Wu of Stony Brook University Cancer Center in New York, who reported his findings in the Journal of the American Medical Association, stated that where patients also undergoing chemotherapy were concerned, the risk of blood clots further increased.

Results showed that 6 percent of patients taking Avastin had severe blood clots in their veins, while 4 percent of the ones being treated via chemotherapy only were reported with the condition.

Given that a large number of people suffering from cancer already have the condition called venous thromboembolism, which means that blood clots form in their veins, Wu stated that both patients and doctors should constantly check for sings of blood clots.

Nevertheless, he added that cancer patients should not stop taking the Avastin drug, even though it increased the risk of venous thromboembolism by an overall 33 percent.

Moreover, the Avastin label itself notifies people of the risks the drug carries, warning that blood clots might form in the arteries and then travel through them, which can cause a stroke or a heart attack.