Abstract 5505: Risk of second malignancies in patients with Chronic Lymphocytic Leukemia: A population based Canadian study

Abstract

Abstract A previous population based study on Chronic Lymphocytic Leukemia (CLL) in Manitoba, Canada, demonstrated that in elderly patients the relative survival is reduced, with the difference being greater in males (Seftel et al. 2009). In this study we evaluated the risk of 2nd cancers in an unselected Canadian CLL population to determine whether 2nd cancers might explain the poor relative survival seen in older men with CLL. All CLL diagnoses in Manitoba (Jan 98-Dec 03) were obtained from the Manitoba provincial cancer registry and a centralized flow cytometry database. All cases were reviewed to confirm the diagnosis of CLL. For each patient, the time at risk was considered from the index cancer diagnosis (CLL diagnosis where CLL is the first primary cancer) to the second primary cancer, date of death or censoring date (Dec 09). The Standardized Incidence Ratio (SIR) was calculated to compare the observed number of second cancers in CLL patients with an expected number derived from age, gender and calendar year specific standardized rates of second malignancies for patients with follicular lymphoma (FL). Of 612 patients, 148 (24%) had a history of a previous cancer and were eliminated from the study. Of the remaining 464 (median age 69 y, F:M ratio 1:1.4) 104 (22.88%) patients eventually developed a second malignancy (median follow up 6.4 y, median time to develop 2nd cancer 3.3 y). CLL patients had a 1.8-fold higher relative risk of a 2nd cancer (95% CI 1.29-2.41) compared to FL patients. SIR was 1.9 when non-melanoma skin cancers were excluded. Patients with FL had a similar incidence of second malignancies, as did patients with other invasive cancers. The most common second cancer among CLL patients was non-melanoma skin cancer, followed by cancers of the digestive organs, prostate, breast and lung. Malignancy was the leading cause of death in CLL patients. In patients with a 2nd cancer, cancers of the digestive organs, lung and brain were the most common causes of death. However, in patients without a 2nd cancer, CLL was the primary cause of death. After cancer, cardiovascular complications and infections were the most common causes of death in CLL patients. This study is unique in that (a) it is a population-based study of CLL patients with a confirmed diagnosis (b) the risk of 2nd cancers was compared with another cancer cohort. FL is an indolent B cell neoplasm that is treated and followed in similar ways to CLL. We demonstrated that CLL patients have a significantly increased risk of developing a 2nd cancer compared to FL patients, and this increase was similar in both genders and in all age groups. Thus, the poor relative survival of older men with CLL cannot be explained by an increased incidence of 2nd cancers. The increased incidence of malignancy in CLL may be related to the immune suppression in this disease or to an inherited predisposition to cancer. Further investigations are underway to better explain our observations. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5505. doi:1538-7445.AM2012-5505