ET in adults ≥60 years: A multicenter real-world study in China

Essential thrombocythemia (ET) is a subtype of BCR::ABL1-negative myeloproliferative neoplasms (MPN), and approximately 50% of patients who are diagnosed with ET are ≥60 years old.¹ The MPN Hub have previously reported on a study investigating key considerations in diagnosing and treating pediatric patients with MPN, with specific mention of ET.  Below, the MPN Hub describes a retrospective analysis evaluating older patients (≥60 years) and the potential need for different treatment strategies and prognosis compared with younger patients (18-59).

Study design¹

This retrospective, real-world analysis compared the differences in the molecular characteristics, risk factors for complications and disease progression, and current treatment status of patients diagnosed with ET from China.¹ Eligible patients:

• Were aged ≥60 years or between 18–59 years (control group)
• Had a diagnosis of ET according to the World Health Organization 2016 criteria²
• Had no previous diagnosis of polycythemia vera, primary myelofibrosis (MF) or prefibrotic primary MF.

Selected baseline characteristics of older patients with ET are shown in Table 1.

Table 1. Baseline characteristics*

L, liter; WBC, white blood count. *Adapted from Fu, et al.1
Characteristics, % (unless otherwise specified)	Hydroxyurea treatment (n = 160)	Interferon α treatment (n = 31)
Sex
Female	51.3	38.7
Male	48.8	61.3
Median age (range), years	67 (60–91)	65 (60–77)
Median WBC (range), x109/L	10.3 (4.5–27.1)	11.34 (5.24–25.7)
Driver mutations
JAK2V617F	67.5	64.5
CALR	14.4	9.7
MPL	2.5	6.5

Results¹

A total of 903 patients were included in the analysis, of which 282 patients were aged ≥60 years and 621 patients were aged between 18-59 years acting as the control population. Older patients (≥60 years):

• Had a significantly different genetic mutation profile compared with the control group (Figure 1).
• Had higher white blood count, neutrophil count and platelet counts compared with the control group.
• Had higher rates of thrombosis before diagnosis (37.23% vs 13.69%) and during follow-up (20.21% vs 4.83%).
• At follow-up, 8.16% of patients had disease progression to MF (2.13% vs 1.61%, p = 0.592) or acute leukemia (6.03% vs 5.48%, p = 0.739) compared with the control group.

RNA, ribonucleic acid.
*Adapted from Fu R, et al.¹

Safety

Among the patients aged ≥60:

• Risk factors for disease progression were presence of palpable splenomegaly, male sex, and presence of ASXL1 and SF3B1 mutations.
• Overall, 34 patients died after a median duration of 45.45 months from diagnosis.
  • Of these patients, 15 died from ET, five from thrombotic complications, one from cerebral hemorrhage, and nine from disease progression.
• More patients died from ET (5.32% vs 1.45%), thrombotic events (1.77% vs 0.16%) and disease progression (3.19% vs 1.13%) compared to the control group.

Real-world treatment status in older patients (≥60 years)¹

According to the National Comprehensive Cancer Network, all patients who are at high-risk for ET should receive cytoreductive therapy combined with antiplatelet drugs.

• In real-world setting, 57.08% of patients were categorized as high-risk and were in line with these guidelines.
• Meanwhile, 50.55% of older patients with ET evaluated in this study were categorized as high-risk and were in line with these guidelines.

Conclusion

This study suggests that patients diagnosed with ET who were aged ≥60 years have different clinical characteristics, molecular profiles, thrombotic and bleeding complications, and prognoses compared with patients aged 18-59 years. These findings indicate that older patients may benefit from different treatment regimens than younger patients and highlights the need for further studies and reviews of clinical practice in this population.