Risk of malignancy associated with chronic lymphocytic leukemia: A population based Canadian study

Abstract

20020 Background: Patients with Chronic Lymphocytic Leukemia (CLL) may have an increased risk of other malignancies. Available literature reports on malignancies that develop after the diagnosis of CLL, but does not discuss malignancies that precede the diagnosis of CLL. Methods: All patients diagnosed with CLL between 01/1998 and 12/2003 were extracted from the provincial cancer registry and a centralized flow cytometry database. All other malignancies were obtained from the cancer registry. Dates of diagnoses were compared. A malignancy within 30 days before or after the diagnosis of CLL was considered synchronous with that diagnosis. Results were compared with the age-adjusted incidence of cancer in the province, excluding CLL. Results: Of the 713 cases of CLL, 333 invasive cancers and 38 in situ neoplasia were identified before, synchronous to, or after the diagnosis of CLL. Synchronous malignancies occurred in 4% of cases. The Standardized Incidence Ratio (SIR) for other malignancy subsequent to CLL was 1.40 (95% confidence interval [CI] 1.09–1.80) derived from 65 tumors for males, and 1.29 (95% CI 0.90–1.80) from 35 tumors for females. Mean time to diagnosis of subsequent cancer was 2.0 years (standard deviation[SD] 1.5). The SIR for other malignancy in the 5 years preceding the diagnosis of CLL was 1.36 (95% CI 0.93–1.94) from 31 tumors for males and 0.77 (95% CI 0.54–1.08) from 35 tumors for females. Mean time from diagnosis of preceding malignancy to CLL was 9.4 years (SD 8.7). Conclusions: In this population based study, patients with CLL are at increased risk of other invasive and in situ cancers. This risk is apparent after but not before the diagnosis of CLL, particularly in males. The mechanism of this increased risk may be acquired with the presence of CLL through an underlying but undetermined mechanism, as opposed to an inherent or more longstanding predisposition to malignancy. No significant financial relationships to disclose.