Platelet activation in patients with colorectal cancer

Aspirin may reduce the risk of colorectal neoplasia at doses similar to those recommended for the prevention of cardiovascular disease. Thus, we aimed to address whether enhanced platelet activation, as assessed by the measurement of the urinary excretion of 11-dehydro-TXB2 (a major enzymatic metabolite of TXB2), occurs in patients with colorectal cancer. In 10 patients with colorectal cancer, the urinary excretion of 11-dehydro-TXB2 was significantly higher than in 10 controls, matched for sex, age and cardiovascular risk factors [1001(205-5571) versus 409(113-984) pg/mg creatinine, respectively, median (range), P<0.05]. The administration of aspirin 50 mg daily for 5 consecutive days to colorectal cancer patients caused a cumulative inhibition of platelet cyclooxygenase (COX)-1 activity either ex vivo, as assessed by the measurement of serum TXB2 levels, or in vivo, as assessed by urinary 11-dehydro-TXB2 excretion. In conclusion, enhanced platelet activation occurs in colorectal cancer patients. Permanent inactivation of platelet COX-1 by low-dose aspirin might restore anti-tumor reactivity.