Introduction: Chronic lymphocytic leukemia (CLL) is characterized by the proliferation of monoclonal B-lymphocytes. MBL (monoclonal B-cell lymphocytosis) is considered a precursor state of the disease. Although CLL is incurable it is an indolent disorder and often detected incidentally on routine blood counts. Until now little information has been available on CLL in Iceland, including the incidence, diagnosis, symptoms or MBL precursor state.  

Material and methods: This is a retrospective, descriptive study including CLL patients diagnosed in Iceland over the years 2003-2013. Registries of patients with a CLL diagnosis were obtained from the Icelandic Cancer Registry, Landspitali National University Hospital and the Medical Center in Mjódd. Medical records were reviewed for information on symptoms, diagnosis and treatment. Survival data and causes of death were obtained from national registries.

Results: The number of patients diagnosed with CLL over the study period was 161 (109 males, 52 females). The calculated incidence was 4.55/100,000, and the age-standardized incidence was 3.00/100,000. Mean age at diagnosis was 70.9 years (range 35-96 years). The Icelandic Cancer Registry lacked information on 28 patients (17.4%). The initial diagnosis of CLL was obtained exclusively with flow cytometry in 47.2% of cases. Symptoms were present at diagnosis in 67 of 151 patients (44.4%). One third of the group received chemotherapy and the average time to treatment was 1.3 years. Five-year survival was 70% and median survival was 9.4 years. Elevated lymphocyte counts (≥4,0x10⁹/L) in peripheral blood prior (0.1 to 13.4 years) to diagnosis of CLL was identified in 85 of 99 CLL patients (85.9%).

Conclusion: The incidence of CLL in Iceland is similar to other Western countries. The registration of CLL cases in the Icelandic Cancer Registry must be improved, especially in cases where diagnosis is based solely on flow cytometry. Elevated lymphocyte counts were present in a large proportion of cases prior to the diagnosis of CLL.

 

Figure 1a. Yearly incidence and gender distribution of CLL/SLL diagnoses during the study period.


Figure 1b. Age of CLL patients at the time of diagnosis (red bars). The population in Iceland stratified according to age group is displayed for comparison (blue line, Statistics Iceland 2013).

Figure 2. The study group. Information on patients diagnosed with CLL were obtained from the Icelandic Cancer Registry (n=133), Landspitali department of hematopathology (n=134) and the Medical Center in Mjódd (n=62).

Figure 3. Method of original CLL diagnosis.

Figure 4. The earliest elevated lymphocyte count per patient prior to CLL diagnosis. Outliers have been removed.

Figure 5. Overall survival for the whole study group and stratified according to age (> or < 70 years). Patients who were diagnosed after 70 years had significantly shorter survival than patients diagnosed prior to the age of 70, p<0,001.

Table I. The number and proportion of patients who reported various clinical symptoms or signs. B-symptoms represent one or more of the following; unexplained fever, weight loss and/or night sweats.

Table II. Results of blood tests at diagnosis. Reference values were obtained from the service manual of the department of laboratory medicine, Landspitali.

Table III. The primary cause of death of 47 deceased CLL patients in the study group.

Table IV. Calculated Rai stage of 133 CLL patients and time-to-treat. There was no statistical difference in time to treatment between patients with intermediate or high Rai stages. However, patients with low Rai stage at CLL diagnosis received treatment significantly later compared to the other two groups (p=0,01).