Determining chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) incidence is challenging for two reasons: cancer registries tend to underreport CLL cases and its diagnostic criteria changed markedly in 2008. No studies have reported incidence rates dealing with both difficulties, and thus CLL/SLL burden in Europe is currently uncertain. Herein, we present accurate CLL/SLL incidence in a Spanish region during 1998-2013, using the population-based Girona Cancer Registry (GCR). We detected an 18.2% under-reporting of CLL/SLL cases when combining records from the GCR and additional information sources (i.e., records of flow cytometry laboratories, hospital registries and hematologists' databases). In addition, age-adjusted rates (using the 2013 European population) changed from 7.57 (95% CI 6.87; 8.30) in 1998-2008 to 6.35 (95% CI 5.51; 7.30) in 2009-2013. Overall, completeness of CLL/SLL data requires accurate diagnosis and reporting of cases. Revision of cancer registry operations to include CLL/SLL-specific surveillance is likely to ensure that the monitoring of this malignancy is entirely accurate.
Keywords: 2008 Guidelines; Cancer registry; Chronic lymphocytic leukemia; Incidence; Under-reporting.