Elevated Platelet Aggregation in Patients with Ovarian Cancer: More than Just Increased Platelet Count

<b>Background:</b> Patients with ovarian cancer have high platelet counts, which correlate with disease burden, incidence, and lethality of blood clots (thrombosis). We hypothesized that elevated aggregation is associated with both increased platelet number and altered behavior of platelets in patients with ovarian cancer. <b>Methods:</b> Healthy controls and patients with suspected or diagnosed ovarian cancer were evaluated for complete blood counts. To evaluate the effects of platelet count versus platelet behavior, equal platelet-rich plasma (PRP) volumes versus equal platelet numbers were used in platelet aggregation assays. Arachidonic acid, adenosine diphosphate, and collagen platelet agonists were used to induce aggregation. Volunteers were grouped into healthy controls (23), benign/borderline cases (7), and cancer cases (25 ovarian, 1 colorectal, and 2 endometrial). <b>Results:</b> The rate and amount of platelet aggregation were higher in patients compared to healthy controls regardless of whether the same platelet number or PRP volume was used. Compared to healthy controls, patients with untreated ovarian cancer exhibited high levels of platelet activation markers, P-selectin (27.06 vs. 31.06 ng/mL, <i>p</i> = 0.03), and beta-thromboglobulin (3.073 vs. 4.091 µg/mL, <i>p</i> = 0.02) in their plasma. The significance of the elevation and its correlations with platelet number or PRP volume varied depending on the agonist. Platelet (305.88 vs. 134.12, <i>p</i> < 0.0001) and white blood cell (8.459 vs. 5.395, <i>p</i> < 0.01) counts (×10⁹/L) were elevated pre-chemotherapy and decreased post-chemotherapy, respectively. <b>Conclusions:</b> Elevated platelet aggregation is caused by both altered platelet number and behavior in patients with ovarian cancer. These results support the study of antiplatelet agents for thrombosis prevention in these patients.