Background
Results of prospective clinical trials for patients with previously untreated diffuse large B-cell lymphoma (DLBCL) suggest that patient sex, weight, and/or body mass index (BMI) impact clinical outcomes. Recent reports implicate differences in rituximab metabolism as the explanation for differences in outcomes for male and female patients.1–3 Analysis of pharmacokinetic data from clinical trial subjects by the German High-Grade Non-Hodgkin Lymphoma Study Group (DSHNHL)3,4 shows that rituximab clearance is relatively slow in elderly (age >60 years) women compared with men, leading to higher blood levels and prolonged exposure to rituximab, possibly explaining the better clinical outcomes observed in elderly women. Specifically, it has been suggested that elderly men are underdosed, based on faster rituximab clearance.
Reports on the impact of BMI on treatment outcomes are conflicting. Analysis of the US Veterans Administration (VA) database shows an association between increased BMI and improved survival in patients with DLBCL,5 whereas similar analyses of the ECOG clinical trial (E4494) for patients with DLBCL aged 60 years and older fail to show either a significant association of BMI with clinical outcomes or a sex difference related to BMI in failure-free survival.6 To further investigate these potential risk factors, we studied the effect of patient sex, BMI, and body surface area (BSA; the actual dosing parameter), and interactions among these factors, on long-term clinical outcomes in patients with DLBCL included in the prospectively collected NCCN Outcomes Database for Non-Hodgkin's Lymphoma, focusing on the elderly subset.
Patients and Methods
Patient Cohort: NCCN NHL Database for DLBCL
The formation and data structure of this multicenter NCCN Outcomes Database for NHL was previously reported.7 There are 7 participating NCCN Member Institutions, including (1) City of Hope Comprehensive Cancer Center, (2) Dana-Farber/Brigham and Women's Cancer Center, (3) Fox Chase Cancer Center, (4) The University of Texas MD Anderson Cancer Center, (5) Roswell Park Cancer Institute, (6) University of Michigan Comprehensive Cancer Center, and (7) Robert H. Lurie Comprehensive Cancer Center of Northwestern University. Sequential patients seen at these centers older than 18 years with newly diagnosed DLBCL between June 1, 2000, and December 31, 2010, were included, with follow-up through December 31, 2011. Patients were required to be cancer-free for 5 years before their lymphoma diagnosis.
Study Cohort
De novo DLBCL cases diagnosed between June 2000 and December 2010 and treated with a rituximab-containing regimen as first-line therapy were included in the main study group. Patients were divided into 2 age subgroups: older than 60 years and 60 years of age or younger. The following additional patient characteristics were extracted from the database: sex, BMI (weight [kg]/height [m]2), BSA (Dubois formula),8 and international prognostic index (IPI) risk category9 based on age, Ann Arbor stage (I–IV), number of extranodal site involvement, lactate dehydrogenase level, and ECOG performance status (0–4). Initial treatment, outcomes, and corresponding event dates were queried related to disease progression or death, or, if neither, date of the last follow-up visit. Patients recorded to have moderate or severe liver disease and/or severe renal insufficiency (glomerular filtration rate <30%) were also identified from the database.
Outcomes and Methods of Analysis
Treatment outcomes were assessed for progression-free survival (PFS) and overall survival (OS) at 3 years for the entire study population and both age subgroups (≤60 and >60 years). PFS at 3 years was the primary outcome, which was determined as the earliest of death, disease recurrence, or indication of disease progression on therapy. PFS was chosen a priori because it better reflects the treatment outcomes associated with initial therapy. OS was the secondary outcome and was defined as death from any cause. The effects of sex, BMI, and BSA on PFS and OS were first studied individually in a Cox regression model. Effects of BMI and BSA on PFS both as continuous variables and as categorical variables based on WHO criteria were examined. BSA was viewed as an index for actual rituximab dosing. The effect of sex with respect to WHO classification of BMI (low, ≤18.5; normal, >18.5–25.0; overweight, >25.0 kg/m2) or BSA (<2, ≥2 m2) were then studied in multivariable model and through stratified analysis using Kaplan-Meier curves and log-rank tests. Interaction terms between sex and BMI, and sex and BSA were tested respectively in the multivariable Cox model. Across participating study centers, no dose capping was mandated for rituximab based on BSA. In a sensitivity analysis, the effect estimate of these factors on PFS and OS was adjusted for the IPI (risk categories: low, low-intermediate, high-intermediate, and high) in the multivariable Cox regression model. Weight alone as a prognostic factor was also examined in the univariate and multivariate analyses, adjusting for sex and age.
Results
The study population consisted of 1,386 adult patients with DLBCL with complete clinical information at baseline, all confirmed to have received rituximab-based first-line immunochemotherapy for DLBCL (Table 1). A total of 146 patients were excluded for missing height, weight, or IPI. The median age of this study population was 58 years (men, 58 years; women, 59 years); 627 patients were older than 60 years. The median follow-up for PFS of the entire cohort was 3 years, and was 2.8 years in the elderly (age >60 years) subset. Most elderly men were
Baseline Characteristics of the NCCN Diffuse Large B-Cell Lymphoma Cohort Who Received Rituximab-Based First-Line Chemoimmunotherapy (n=1,386)

Individual Effects of BMI, BSA, and Sex on Clinical Outcomes
When BMI and BSA were considered as continuous variables, the effect of BMI on disease progression or death (PFS) varied across its range, with a higher risk associated with low BMI and the risk decreasing as BMI increased (Figure 1A). Similarly, risk of disease

Change of risk on 3-year progression-free survival across range of (A) body mass index (BMI) and (B) body surface area (BSA) in terms of estimated hazard ratios (HR; red) and CI band (blue).
Citation: Journal of the National Comprehensive Cancer Network J Natl Compr Canc Netw 14, 10; 10.6004/jnccn.2016.0136
Effect of Sex in Relation to the Levels of BMI and BSA and Patient Age
Among all patients, male sex was associated with worse clinical outcomes after adjusting for age and BMI or BSA (3-year PFS: HR, 1.4 and 1.5, respectively; P<.01). (Table 3). Of note, the magnitude of risk associated with male sex on survival diminished with increasing BMI (≤18.5 kg/m2, >18.5–25.0 kg/m2, >25 kg/m2) and BSA (<2 m2, ≥2 m2) (Figure 2B–C). Compared with men, women showed a significantly lower risk of 3-year PFS in the normal BMI category (log-rank, P<.01), whereas the sex difference in risk was no longer present in the high BMI group (log-rank, P=.29). Similarly with BSA, the sex difference in survival was most apparent in the normal BSA group (<2 m2), in the group with BSA of 2 m2 or more. HR estimates for sex, BMI, and BSA remained largely unchanged after adjusting for IPI in the multivariable model. Normal BMI versus high BMI independently predicted poor outcomes (3-year PFS: HR, 1.5; P<.01; OS: HR, 1.6; P<.01) after adjusting for sex, as did BSA (<2 m2 vs ≥2 m2), which correlated with a lower risk of 3-year PFS (HR, 1.4; P=.03) (Table 3). Weight itself, irrespective of height or BMI, was not a significant prognostic factor for PFS (3-year HR, 0.99; 95% CI, 0.99–1.00; P=.09) or OS (3-year HR, 1.00; 95% CI, 0.99–1.01; P=.32) after adjusting for sex and age.
Specifically, in the elderly age subgroup (n=627), high BMI remained protective. The sex difference in effect on PFS attenuated with increase in levels of BMI and BSA. Notably, the poor risk associated with male
Univariable Analysis of Effect of Age, Sex, BMI, and BSA on Treatment Outcomes in Patients With DLBCL Who Received Rituximab-Containing First-Line Therapy (n=1,386)


Kaplan-Meier curves showing effect of sex on 3-year progression-free survival (PFS) stratified by the (A) age groups, (B) levels of body mass index (BMI), and (C) body surface area (BSA) in all patients.
*P is significant (ie, <.05).
Citation: Journal of the National Comprehensive Cancer Network J Natl Compr Canc Netw 14, 10; 10.6004/jnccn.2016.0136
Discussion
The addition of rituximab to front-line anthracycline-containing regimens for patients with DLBCL has been shown to improve outcomes in both men and women, young and old. Several analyses have shown greater benefit in women, especially among the elderly, attributed to slower clearance of rituximab, resulting in higher and more prolonged rituximab levels.1,3 These findings raise the issue of potential rituximab underdosing and suboptimal clinical outcomes in elderly men. In this analysis of clinical outcomes of nearly 1,400 patients with newly diagnosed DLBCL enrolled in the NCCN Outcomes Database for NHL, we have confirmed previous reports of an age-related disadvantage to male sex. Furthermore, we found that this effect on patient outcomes is abrogated by higher levels of BMI and BSA in most North American patients with DLBCL.
Our results, derived from real-world clinical experience at 7 NCCN Member Institutions, confirm and extend those reported by others that were based exclusively on patients enrolled on clinical trials.1,6,10 We report that in the rituximab era, male sex is associated with a higher risk of disease progression and death than female sex, and that the difference in PFS results primarily from the elderly patient subgroup (>60 years). The difference between older women and men is as yet unexplained and may reflect the comparatively better survival of women versus men in the general population. An alternative explanation suggested by detailed pharmacokinetic studies of elderly clinical trial subjects1,3 receiving rituximab-containing chemotherapy is that a more pronounced age-dependent decline in rituximab clearance in women compared with men underlies the comparatively better outcomes observed in elderly women.
In terms of the role of patient body habitus, previous studies have investigated the impact of weight and BMI on clinical outcome with mixed results. Analysis of the RICOVER-60 trial suggests that the addition of rituximab to conventional therapy has differential effects related to body weight.3 Patients in the lowest weight quartile experienced significant improvement in PFS with the addition of rituximab, whereas the top weight quartile had only a minor improvement in outcomes. In our analysis of the NCCN Outcomes Database, we used BMI and BSA to better reflect body habitus. We show that high BMI (>25 kg/m2) favorably influences treatment outcomes
Multivariable Analysis of Effect of Sex, BMI, and BSA on Treatment Outcomes Divided by Age Group in Patients With DLBCL Who Received Rituximab-Containing First-Line Therapy (n=1,386)

Our analysis suggests that high BMI is protective among elderly patients with DLBCL treated with rituximab-containing chemotherapy. In particular, high BMI/BSA in this North American elderly DLBCL population compensates for the negative impact of male sex. Whether the slightly higher total dosing of larger patients underlies this observation is unclear. Higher body weight has been associated with faster rituximab clearance,3 and would therefore not be expected to improve outcomes for men through its effect on rituximab pharmacokinetics. Our analysis of real-world treatment data did not suggest that patient

Kaplan-Meier curves showing effect of sex on 3-year progression-free survival (PFS) stratified by the levels of (A) body mass index (BMI) and (B) body surface area (BSA) in the elderly group (aged >60 years).
Citation: Journal of the National Comprehensive Cancer Network J Natl Compr Canc Netw 14, 10; 10.6004/jnccn.2016.0136
Conclusions
This analysis of a large unselected North American DLBCL patient cohort treated with rituximab-based chemoimmunotherapy confirms an age-dependent disadvantage to male sex in treatment outcomes. This effect diminishes with higher levels of BMI and BSA, and impacts patients mainly of normal or low BMI/BSA, the minority of patients with DLBCL in North America. These findings do not exclude the possibility that higher doses of rituximab or different scheduling could benefit subsets of patients, as suggested by preliminary results from the randomized phase II SEXIE-R-CHOP-1416 and analysis of the SMARTE-R-CHOP-14 trial.17 Our findings support continued efforts to optimize rituximab dosing, especially in elderly men with a BMI of 25 kg/m2 or less or BSA of 2 m2 or less. Future prospective trials should factor body habitus and sex into the study design and analysis.
The authors wish to acknowledge the patients and staff of the NCCN Member Institutions participating in the lymphoma database for their contributions.
The authors have disclosed that they have no financial interests, arrangements, affiliations, or commercial interests with the manufacturers of any products discussed in this article or their competitors. The NCCN non-Hodgkin's lymphoma database project was reviewed by the Institutional Review Board and received approval at each participating institution. Dr. Zhou was supported by the National Institutes of Health (NIH) Fellowship Training Grant (T32) under the award number (T32 CA 79447-15).
The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.
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