Hairy Cell Leukemia – A Mortality Analysis

Objectives.—To assess mortality and survival analysis for patients with hairy cell leukemia, taking into consideration the effect of new therapies. Background.—Hairy cell leukemia (HCL) is a chronic B-cell disorder and an uncommon malignancy. Initially, therapeutic options were limited, and outcomes were poor. However, with the introduction of alpha interferon in 1984, followed by two purine nucleoside analogues pentostatin (1986) and cladribine (1990) and more recently, rituximab, a monoclonal antibody, HCL outcomes have improved, translating HCL from a disease with limited treatment options to a highly treatable disease with a near-normal survival. Methods.—A SEER-17 database survival analysis was conducted on patients diagnosed with HCL in the US. Using the International Classification of Diseases code for HCL (9940), the SEER database was interrogated for patients diagnosed from 1973-2013. Analysis was based on comparing the survival of patients in the last 4 decades to the expected survival population generated by the SEER data. Analysis using mortality and survival methodology was used to calculate the excess death rate (EDR), mortality ratios, and survival ratios. Results.—In patients with HCL diagnosed from 1973-1983 compared to those diagnosed from 1984-1993, the survival improved by 6% in the first year and reached 26% by year 5, 30% by year 10, 33% by the year 15, and 40% by year 20. Calculations of relative mortality showed a decrease in mortality from decade 1973-1983 to decade 1984-1993 of 66% in the first year, 96% by year 5, 66% by year 10, 46% by year 15, and 40% by year 20. Conclusions.—The survival of patients diagnosed with HCL has improved over the last 3 decades, with a significant benefit being seen since 1984. Thanks to the introduction of newer drugs, the outcome of patients with HCL has been transformed into a highly treatable form of leukemia, and patients now have a near-normal life expectancy.