Chronic Lymphocytic Leukemia-Associated Chromosomal Abnormalities and Risk of Secondary Malignancies

Introduction: Incidence of secondary malignant neoplasm in patients with chronic lymphocytic leukemia (CLL) is already established. Genetic predisposition has been considered to be a possible contributory factor for the preponderance of second cancers in this population. In the present study, we examined the frequency, characteristics, and clinical outcomes of secondary malignancies in patients with CLL based on their Interphase fluorescence in situ hybridization (FISH) panel.

Methods: We reviewed the medical records of consecutive patients with CLL observed or treated at Ellis Fischel Cancer Center during the period from 2007-2014. We collected demographic data, CLL Rai stage, treatment history, Interphase fluorescence in situ hybridization (FISH) panel results and the presence of a secondary malignancy (skin cancers, solid tumors and hematologic malignancy excluding CLL transformation).Our aim was to investigate the association between secondary malignancy and chromosomal abnormalities and other risk factors using Chi²test for categorical variables and Wilcoxon rank-sum test for continuous variables. Cox proportional hazard models and logistic regression models were used to evaluate risk factors of developing secondary malignancy and overall survival.

Results: We identified 142 CLL patients who were either observed (n=62) or had a history of treatment (n=80) for CLL. 67% were male and 33% were female. 85% of patients were Caucasians, 10% African Americans, and 5% other. Familial CLL was present in 6% of cases. 51% of patients were non-smokers. 5% of patients had cancers preceding the diagnosis of CLL (non-melanoma skin cancers=3, melanoma=1, Hodgkin's lymphoma=1, Prostate=2). 28% of patients developed secondary malignancies after the diagnosis of CLL; among them non-melanoma skin cancers were the most common (78%), followed by cutaneous melanoma (9.5%) and papillary thyroid cancer (4.7%). Other malignancies included lung (2.3%), kidney (2.3%), prostate (2.3%) and ocular melanoma (2.3%). 12% patients had aggressive non-melanoma recurrent skin cancers that require multiple treatments along-with systemic therapy for progressive CLL.

CLL-FISH panel at diagnosis was available in 98 patients. Among these patients,13q deletion was present in 45%. Within the 13q deletion group, secondary malignancy was noted in 50% during a median follow up of 7 years. All cases of papillary thyroid cancers were also present in 13q deletion. In contrast, 11q deletion was detected in 15% and trisomy 12 in 18% of patients with incidence of secondary malignancy 40% and 10%, respectively. No solid malignancy other than skin was identified in the 11q deletion and trisomy 12 groups. 17p deletion was present in 5% of cases and 60% of 17p deletion cases had secondary cancers (skin 80%). Normal FISH panel was present in 17% cases and 20% of normal FISH had secondary malignancy (solid 10%, skin 10%).

The median overall survival time is 6 years for the entire cohort (IRQ: 3-9 years). Secondary malignancy was associated with worse overall survival (OS) (HR=0.57, 95% CI:0.33-0.98, p=0.04) compare to patients who did not have secondary malignancy. The risk of secondary malignancy is increased in patients with advanced age (OR=1.05, 95% CI:1.00-1.10, p=0.04) and in those who were treated with alkylating agent for CLL OR=6.62, 95% CI:2.08-21.03, p=0.001. However, there were no significant difference on risk of developing secondary malignancy based on specific chromosomal FISH result, Rai stage, smoking, family history and gender.

Conclusion: Secondary malignancies are frequent in patients with detectable chromosome abnormality on FISH panel. However, the increased risk of secondary malignancy does not correlate with specific cytogenetic abnormality. Non melanoma skin cancers are exceedingly common in CLL patients and carries aggressive couse in progressive CLL patients. Larger studies are required to identify subtype of CLL based on integrated mutational and cytogenetic subgroup that are at increased risk of specific secondary malignancies.