Anticoagulant therapy is associated with improved biochemical control of localized prostate cancer treated with radiation, especially among patients with high-risk disease, according to researchers.

Kevin S. Choe, MD, PhD, of the University of Chicago’s Pritzker School of Medicine, and colleagues studied 662 men with prostate cancer who underwent radiotherapy with either external beam radiation, permanent seed implantation, or both. Of these, 243 (37%) were receiving anticoagulants (warfarin, clopidogrel and/or aspirin) and 419 were not (controls).

At a median follow-up of 49 months, the four-year rate of freedom from biochemical failure (FFBF) was significantly better in the men who received anticoagulants than those who did not (91% vs. 78%), the investigators reported in Cancer (2010; published online ahead of print).

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After adjusting for potential confounders, anticoagulant treatment was associated with a 46% decreased risk biochemical failure, which the researchers defined as a PSA increase greater than 2 ng/mL from the post-treatment nadir. The rate of distant metastases at four years also was significantly decreased in the anticoagulant group (1% vs. 5%).

The four-year overall survival rate was 92.2% and 90.3% for the anticoagulant and control arm, respectively, a nonsignificant difference between the groups.

In subgroup analyses, the improvement in biochemical control was significant only among the men with high-risk disease (defined as either a PSA level above 20 ng/mL, a Gleason score of 8 or higher, or T3 disease). In this group, patients receiving anticoagulants had a four-year FFBF rate of 82.4% compared with 57.6% among men not on anticoagulants.

After adjusting for potential confounders, anticoagulant therapy was independently associated with improved biochemical control, as were Gleason score, initial PSA, and T classification.

In addition, the study showed that patients who received a radiation dose of 72 Gy or greater had a 49% decreased risk of biochemical failure compared with men who received a lower dose.

Dr. Choe’s group noted that association between cancer and the coagulation system is well recognized, and that substantial experimental data suggest that the coagulation system may modulate multiple cancer pathways, such as angiogenesis, tumor proliferation, and metastasis.

“The current study suggests that anticoagulants may have an antineoplastic effect in prostate cancer,” the authors concluded. “The mechanism of the antineoplastic effect remains speculative, but it may work by suppressing metastasis.”