Thromboembolic events were common and predominantly arterial in this Asian PV cohort, occurring mainly before or at diagnosis, and prior thrombosis was associated with inferior survival.
Key Findings
Results
More than one-third of Thai PV patients experienced at least one thromboembolic event, with the vast majority occurring before or at diagnosis.
51 of 133 patients (38.3%) experienced at least one thromboembolic event, with 54 total events.
87% of thromboembolic events occurred before or at PV diagnosis.
Arterial thrombosis accounted for 90.7% of all events.
The cohort included 133 patients with a median age of 61 years (range 18–88), 60.2% male, from a single tertiary referral center.
Results
Age ≥60 years was significantly associated with thromboembolic events.
Odds ratio for thromboembolic events in patients aged ≥60 years was 2.34 (95% CI, 1.07–5.11).
This was identified as a statistically significant association.
The median age of the cohort was 61 years.
Results
Prior thrombosis was associated with an increased risk of death.
Hazard ratio for death associated with prior thrombosis was 1.98 (95% CI, 1.15–3.42).
The 5-year overall survival for the full cohort was 82.7% (95% CI, 74.61–88.35).
Median follow-up was 7.7 years.
Results
Hydroxyurea resistance or intolerance occurred in approximately one in ten patients.
Hydroxyurea resistance or intolerance was observed in 9.8% of patients.
This finding was noted during long-term follow-up with a median of 7.7 years.
Results
Bleeding complications, including major bleeding, were observed in a minority of patients.
Bleeding complications occurred in 6.8% of patients.
Major bleeding occurred in 4.5% of patients.
Results
Disease transformation and secondary solid malignancies occurred at notable rates during long-term follow-up.
Fibrotic transformation occurred in 4.5% of patients.
Leukemic transformation occurred in 3.8% of patients.
Secondary solid malignancies occurred in 6.0% of patients.
These findings underscore the importance of continued long-term surveillance in PV patients.
Background
Data on thrombotic burden and long-term outcomes in Asian PV patients were previously limited, motivating this retrospective cohort study.
The study was a retrospective cohort conducted at a single tertiary referral center in Thailand.
A total of 133 patients were included.
The study evaluated thromboembolic events, treatment-related complications, disease progression, and overall survival.
What This Means
This research examined what happens to patients in Thailand who have polycythemia vera (PV), a blood disorder where the body makes too many red blood cells. The study followed 133 patients for a median of nearly 8 years and found that blood clots (thrombosis) were very common — more than a third of patients had at least one clotting event. Strikingly, most of these clots (87%) happened before or at the time PV was actually diagnosed, suggesting that a clotting event is often what first brings the disease to medical attention. Nearly all clotting events were arterial (affecting arteries rather than veins), which is somewhat different from patterns sometimes reported in Western populations.
The study also found that patients who had experienced a prior blood clot had nearly twice the risk of dying compared to those who had not, and that being aged 60 or older roughly doubled the odds of having a clotting event. Over the long follow-up period, small but meaningful proportions of patients developed serious complications: about 1 in 25 developed scarring of the bone marrow (fibrotic transformation), about 1 in 26 developed leukemia, and 1 in 17 developed a second, unrelated cancer. About 1 in 10 patients could not tolerate or did not respond adequately to the standard drug hydroxyurea.
This research suggests that in Asian PV patients, clotting — especially arterial clotting — is a major concern that often predates diagnosis and worsens long-term survival. It highlights the need for early detection of PV in patients presenting with unexplained clots, careful long-term monitoring for disease progression and secondary cancers, and continued study of outcomes in non-Western populations, who have historically been underrepresented in PV research.
Hantrakun N, Tantiworawit A, Norasetthada L, Rattarittamrong E, Chai-Adisaksopha C, Rattanathammethee T, et al.. (2026). Thrombotic burden and longitudinal outcomes in Thai patients with polycythemia vera.. Annals of medicine. https://doi.org/10.1080/07853890.2026.2682982