ABSTRACT
Chronic lymphocytic leukemia (CLL) is the most common form of leukemia among older
adults in western countries, accounting for around 30% of all leukemias (1), though in a
proportion of cases it can present with lymphoadenomegaly with a limited, if any, peripheral
blood involvement (defined as “Small Lymphocytic Lymphoma” - SLL). Data from the
United States Surveillance, Epidemiology, and End Results (SEER) Registry estimate the
U.S. incidence between 1996 and 2000 to be 3.7 per 100,000 individuals per year, being
rather stable over the past decades (2,3). The median age at diagnosis is 72 years (4),
though, in recent years, one-third of new cases are diagnosed before the age of 55 years
(5), indicating an increase in the incidence among younger individuals. Given the long
median survival of the disease (around 10 years), prevalence of CLL is 0.03% to 0.05%,
i.e., 30 to 50 individuals affected among 100,000 citizens. Overall, CLL diagnosis may be
underestimated because of underreporting and incomplete case ascertainment (6), which
did not change over the last 40 years (3). Age-adjusted incidence rates for CLL/SLL were
70% to 90% higher among males than females, with a sex ratio of about 1.5-2:1 (1).
Although male gender is an important risk factor for most hematological malignancies
(7,8), the causal factors underlying this association are unknown. Occupational exposures
are always of potential concern in male-predominant cancers.
