Epidemiological Insights into Large Granular Lymphocyte Leukemia: A Nationwide SEER Database Study

Background: Large granular lymphocytic (LGL) leukemia is a rare hematological malignancy that arises from cytotoxic T lymphocytes (T-LGL) or natural killer (NK) cells. LGL leukemia accounts for 2% to 5% of chronic lymphoproliferative disorders in the United States of America. LGL leukemia can either present as an indolent type or an aggressive type. Most patients remain asymptomatic and often have associated autoimmune diseases, such as rheumatoid arthritis and hematologic dyscrasias. We analyzed the demographic characteristics of LGL leukemia patients and investigated the influence of social determinants on their survival.

Methods: We performed a retrospective cohort study of the Surveillance, Epidemiology, and End Results (SEER) database for patients diagnosed with LGL leukemia between years 2000 and 2020. Patient demographics, year of diagnosis, and timeline of treatment were analyzed by descriptive statistics. Cox proportional hazards regression analysis was performed to identify the factors influencing the survival of these patients.

Results: A total of 2589 patients were diagnosed with LGL leukemia. Median age of diagnosis was 67 years. 59.4% were aged more than 65 years of age at the time of diagnosis, 52.7% were males, 81.5% were Caucasians, 64% had an annual income of more than $65,000, and 84.2% lived in metropolitan areas. 91.8% were diagnosed in the past decade after 2010. It is worth noting that 64.5% of the patients received treatment more than six months after diagnosis of LGL leukemia. 81.5% of patients were Caucasians, 9.6% were African Americans, 5.3% were Asians/Pacific Islanders, followed by 2% Hispanics and 1.5% American Indians. At the time of the last follow-up, 65.5% of patients were alive, with an overall median survival of forty months. 70% of patients had LGL leukemia as the only primary malignancy. Age less than 65 years had better outcomes than the older age group (HR 0.32). Female gender was protective (HR 0.69). Poor outcomes were seen in patients with an annual income of less than $65,000 (HR 1.21). The year of diagnosis and residence had no significant effect on survival. Marriage improved the outcomes of patients (HR 0.78) (Table 1). Patients receiving treatment within six months of diagnosis had higher mortality (HR 1.43) than the rest of the population. Caucasians comprised majority of the patient population and had better prognoses (HR 0.11) than Asians/Pacific Islanders (HR 0.49), Hispanics (HR 0.82), and African Americans (HR 0.97) (Figure 1).

Conclusion: We present a population-based analysis and the determinants of survival in patients with LGL leukemia, a rare malignancy. The number of cases has increased in the past decade. Significant patient factors influencing survival in LGL leukemia patients include younger age at diagnosis, female gender, marriage and higher annual income.