Outcomes and Causes of Mortality in Polycythemia Vera in a Distinct Demographic: Adolescents and Young Adults

Abstract

Background Polycythemia vera (PV) is an uncommon hematologic malignancy that occurs predominantly in older populations with an overall median age of 61 years, with less than 10% occurring below 40 years. 1 The adolescent and young adults (AYA) age group is defined as young people between 15 to 39 years of age. 2 There is a paucity of information on PV in AYA in the literature. We aimed to examine the outcomes and causes of death in PV in AYA and compare them with older people aged 40 years and above. Methods Cases of PV were identified from the Incidence-Surveillance, Epidemiology, and End-result (SEER) Research Plus Data, 17 Registries (2000 - 2020) using the International Classification of Diseases for Oncology, 3rd Edition (ICD-O-3) code 9950. Only primary cases were included. Patients' characteristics (sex, race, and causes of death) were obtained from the database. Those without microscopic or laboratory diagnosis, unknown race, cause of death, or survival were excluded. Descriptive statistics (frequencies and median) were compared with the Chi-squared test between the AYA and older population. The Kaplan-Meier method was used to estimate median overall survival (OS). Cox regression analysis was done to determine predictors of survival in both age groups. Results We identified 10,696 patients with PV within our study period of 2000 - 2020. Out of these, only 7.8% (n=830) were in the AYA cohort compared to 92.2% of the patients aged ≥ 40 years. The median age was 33 years (IQR: 27 - 37) in AYA and 65 years (IQR: 55 - 75) in the older group. There were more males (70% vs. 55%, p<0.001) but a lower proportion of Whites (67% vs. 78%, p<0.001) in the AYA group than in the older group. As shown in Figure 1, the causes of death (COD) were similar between AYA and older patients except for myeloproliferative/myelodysplastic syndromes, which was more common in the older people compared to AYA (15.4% vs. 3.7%, p=0.018). Conversely, non-disease causes of death (accidents, adverse events, suicides/self-inflicted injuries etc) were more frequent in the AYA group than in the older group (16.7% vs. 4.4%, p=0.001). The five and 10-year overall survival (OS) were 97.0% and 93.4%, respectively, in the AYA, but 81.2% and 63.4%, respectively, in the older group. On multivariate analysis, as shown in Table 1, there was no association between sex, race, geographical location, and survival in the AYA cohort, except higher income status was associated with reduced odds of mortality. In the older group, male sex (HR=0.74, 95% CI: 0.69 - 0.80) and diagnosis of PV between 2011 - 2020 (HR=0.65, 95% CI: 0.60 - 0.71) were independent predictors of better survival outcomes. Non-Hispanic White (HR=1.36, 95% CI: 1.17 - 1.57) and Black races (HR=1.47, 95% CI: 1.21 - 1.79), and living in a non-metropolitan area (HR=1.12, 95% CI: 1.02 - 1.23) were associated with poor survival in the older group. Conclusion Polycythemia Vera, though rare in AYA, seems to have good survival outcomes in this group. We observed that compared to the older population, AYA were more likely to die from non-disease causes and less frequently from myeloproliferative/myelodysplastic syndromes. Improved income status appears to favor survival outcomes in AYA.