Prevalence and the impact of hypogammaglobulinemia in newly diagnosed chronic lymphocytic lymphoma patients

Abstract Objective To examine the prevalence of hypogammaglobulinemia in chronic lymphocytic lymphoma (CLL) patients and to test the hypothesis that patients with hypogammaglobulinemia have a distinct clinical profile and outcome. Methods Immunoglobulin levels (IgA, IgG, IgM, IgE) were measured in newly diagnosed, treatment naïve banked samples of 150 patients with CLL followed prospectively for outcomes. Cox regression models were used to assess the effects of clinical variables on overall survival (OS). Results The median age of the selected CLL cohort was 64 years with a male predominance; 96.2% of the patients were white. Fifty‐nine deaths occurred during a median follow up of 6.8 years. Hypogammaglobulinemia in CLL was common in our cohort with 88 (58.7%, 95% CI: 50.4‐66.6%) patients having a measurable isotype deficiency. The most common Ig deficiency was IgM (44.0%). IgA deficiency or low IgE was associated with higher Rai stages as well as with higher white blood cell counts at presentation. Any immunoglobulin deficiency was not associated with overall survival. Conclusion A significant proportion of treatment‐naïve CLL patients had underlying Ig deficiencies – both in isolation and in isotype combinations. Although a deficiency of IgA or IgE was associated with more severe disease at presentation, the impact of this association was mild.

CLL is a heterogeneous disease with probably several different etiologies all resulting in clonal B cell proliferation. The two best established CLL prognostic markers are TP53 aberration and the mutational status of the variable region of the immunoglobulin heavy chain (IGHV) gene [12] These markers provide valuable but incomplete information on pace of disease progression, response to certain therapeutic strategies and expected overall survival. Neither marker substantially informs on the relationship of the disease to other underlying immune dysfunction or risk of infectious complications. A further understanding of the heterogeneity of CLL could be of value in providing more personalized therapy with current treatment options, as well as better understanding the biology needed to develop future treatment options.
Hypogammaglobulinemia can be seen in primary immunodeficiencies, for example, in common variable immunodeficiency (CVID), or be secondary to other processes such as malignancy, drug induced, or infectious [13]. A deficiency of an Ig isotype is usually defined by levels below two standard deviations of the mean of a normal cohort.
Although routine measurement of IgE is not part of the work up of hypogammaglobulinemia, Lawrence et al [14] have shown that an undetectable IgE (<2 IU/mL) occurs in only 3.3% of the general population in contrast to 75.6% of patients with CVID. Their findings support the routine measurement of serum IgE in the work up of patients with hypogammaglobulinemia.

The University of Iowa/Mayo Clinic Molecular Epidemiology
Resource (MER) is an established resource for discovery of biomarkers in lymphoid malignancies and provides a tool to evaluate the significance of hypogammaglobulinemia in newly diagnosed patients with CLL. This prospectively assembled cohort of newly diagnosed patients with lymphoproliferative disease collects baseline biologic specimens and ongoing patient clinical outcomes with sufficient duration of follow-up to assess relevant associations in a heterogeneous disease with indolent behavior [15].
There is inconsistency regarding the association between hypogammaglobulinemia and survival in CLL with some studies reporting worse survival [6,9] while other studies finding no evidence of an association [16,17]. Two contemporary studies evaluated the prevalence of hypogammaglobulinemia in CLL and neither studied the prevalence and impact of low IgE on outcomes in CLL [8,9]. Therefore, the objective of this study was to examine the prevalence of hypogammaglobulinemia, examining all isotypes, in newly diagnosed CLL patients and to test the hypothesis that patients with hypogammaglobulinemia have a distinct clinical profile and outcome.  [19]. To be eligible for this study, the patients had to be treatment naïve at the time of serum collection. Baseline clinical, laboratory, and treatment data were abstracted from medical records using a standardized protocol. Participants provided peripheral blood serum samples and were systematically followed every 6 months for the first 3 years, and then annually thereafter. Disease progression (ie, requirement for treatment) and deaths were verified through medical record review. Patients' reports of no disease progression were verified on an annual basis. The cohort protocol was approved by the institutional review boards at the Mayo Clinic and the University of Iowa and written informed consent is obtained from all participants.

Patient cohort and baseline characteristics
IgG/A/M levels were measured using immunoturbidimetric assay whereas the IgE level was determined using electrochemiluminescence immunoassay. The values of normal range used in our laboratory were used to define cut-offs for low levels -IgG (<700 mg/dL) and IgM (<40 mg/dL). Low IgA was defined as IgA (<70 mg/dL), and based on prior literature [14], low IgE was defined as IgE (<2 IU/mL).

Patients
From   Figure 1). The strongest correlation among isotype deficiencies was between IgG and IgM (ɸ = 0.43) with the remaining associations ranging from 0.14 to 0.29. The mean and median values for each immunoglobulin subtype is presented in Table 2.

Association of hypogammaglobulinemia with clinical presentation and clinical outcomes
Presence of any hypogammaglobulinemia was not associated with gender, stage at presentation, age, or WBC count at presentation, but some differences were seen for specific isotypes (Table 1). IgA (Table 3) deficiency or low IgE (Table 4) were significantly associated with higher Rai stages as well as with higher white blood cell counts at presentation.
No association was noted between clinical features at presentation and deficiencies in IgG or IgM (Tables S1 and S2).

F I G U R E 2 Association of Ig deficiencies with overall survival
Median TFS was 6.9 years with 72 (48.0%) patients receiving an initial one course of active treatment. Treatment-free survival did not significantly differ by hypogammaglobulinemia.
Median survival for the entire cohort was 12.7 years with no significant difference between those with any immunoglobulin deficiency (12.2 years) and those with normal immunoglobulin levels (12.8 years; Figure 2). No overall or treatment free survival difference was noted for any specific isotype deficiency (Table S3). Furthermore, multiple deficiencies were not associated with any identifiable difference in clinical outcomes. The specific combination of deficiencies in IgG and IgMpotentially a screening sign for patients with common variable immunodeficiency -was not associated with a difference in overall survival.

DISCUSSION
We observed a high prevalence of hypogammaglobulinemia in newly A recent study found both reduced and elevated levels of IgG and IgA at diagnosis are important and independent prognostic markers for infection in CLL, with IgA being more relevant as a marker of disease progression and survival [11]. To the best of our knowledge, our study is the first to report on the levels of all Ig isotypes, including low IgE.
There is no consensus regarding the impact of hypogammaglobulinemia on overall survival in CLL (Table 5). This is due to heterogeneous CLL cohorts between studies and the measurement of only single immunoglobulin class in some studies rather than all Ig classes.
Andersen et al [9] found any Ig deficiency to be associated with worse overall survival, although Parikh et al [8] with the largest study did   [14,22]. This strategy might help identification of patients with primary immunodeficiency. In our study, we did find that 16.7% of our cohort of CLL patients were low in IgE and it was associated with higher Rai stages as well as with higher white blood cell counts at presentation.
Although the association of pretreatment hypogammaglobulinemia with overall survival is uncertain, most studies including ours show clear association with stage, a marker of disease burden, and possibly duration of having CLL [8,9,23] that explained the shorter time to the first treatment in these studies. Hypogammaglobulinemia is likely a consequence of the oncogenic process of CLL since it is rarely found prior to a few years before the diagnosis [24]; however, the exact process is unknown. This seems to be in concordance with the data from multiple myeloma that immunoparesis (deficiency of non-clonal immunoglobulins) is associated with the stage at the time of diagnosis [25,26]." Our study has a few limitations: the study population was predominantly Caucasian, limiting the generalizability of our results to other ethnicities. It is difficult to capture response rates -and consequently progression using rigorous iwCLL response definitions [27] in an observational study, thus we relied on time to treatment as a surrogate measure of short-term disease behavior and response to therapy. One of the major strengths of this study is the use of the lymphoma molecular epidemiology resource-prospective enrollment of consecutive lym-