Occupation and Risk of Non-hodgkin Lymphoma and Its Subtypes

A Pooled Analysis From the InterLymph Consortium

Andrea 't Mannetje; Anneclaire J. De Roos; Paolo Boffetta; Roel Vermeulen; Geza Benke; Lin Fritschi; Paul Brennan; Lenka Foretova; Marc Maynadié; Nikolaus Becker; Alexandra Nieters; Anthony Staines; Marcello Campagna; Brian Chiu; Jacqueline Clavel; Silvia de Sanjose; Patricia Hartge; Elizabeth A. Holly; Paige Bracci; Martha S. Linet; Alain Monnereau; Laurent Orsi; Mark P. Purdue; Nathaniel Rothman; Qing Lan; Eleanor Kane; Adele Seniori Costantini; Lucia Miligi; John J. Spinelli; Tongzhang Zheng; Pierluigi Cocco; Anne Kricker

Disclosures

Environ Health Perspect. 2016;124(4):396-405. 

In This Article

Abstract and Introduction

Abstract

Background: Various occupations have been associated with an elevated risk of non-Hodgkin lymphoma (NHL), but results have been inconsistent across studies.

Objectives: We investigated occupational risk of NHL and of four common NHL subtypes with particular focus on occupations of a priori interest.

Methods: We conducted a pooled analysis of 10,046 cases and 12,025 controls from 10 NHL studies participating in the InterLymph Consortium. We harmonized the occupational coding using the 1968 International Standard Classification of Occupations (ISCO-1968) and grouped occupations previously associated with NHL into 25 a priori groups. Odds ratios (ORs) adjusted for center, age, and sex were determined for NHL overall and for the following four subtypes: diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), and peripheral T-cell lymphoma (PTCL).

Results: We confirmed previously reported positive associations between NHL and farming occupations [field crop/vegetable farm workers OR = 1.26; 95% confidence interval (CI): 1.05, 1.51; general farm workers OR = 1.19; 95% CI: 1.03, 1.37]; we also confirmed associations of NHL with specific occupations such as women's hairdressers (OR = 1.34; 95% CI: 1.02, 1.74), charworkers/cleaners (OR = 1.17; 95% CI: 1.01, 1.36), spray-painters (OR = 2.07; 95% CI: 1.30, 3.29), electrical wiremen (OR = 1.24; 95% CI: 1.00, 1.54), and carpenters (OR = 1.42; 95% CI: 1.04, 1.93). We observed subtype-specific associations for DLBCL and CLL/SLL in women's hairdressers and for DLBCL and PTCL in textile workers.

Conclusions: Our pooled analysis of 10 international studies adds to evidence suggesting that farming, hairdressing, and textile industry–related exposures may contribute to NHL risk. Associations with women's hairdresser and textile occupations may be specific for certain NHL subtypes.

Introduction

Non-Hodgkin lymphoma (NHL) comprises a group of malignancies that are common in industrialized countries. Studies of occupational risk factors have proven valuable for generating hypotheses regarding the possible environmental causes of NHL, and over the past four decades, these studies have produced a number of strong leads (Schottenfeld and Fraumeni 2006). In particular, occupations involving exposure to pesticides and solvents have been repeatedly associated with NHL. Other occupational risk factors have been hypothesized; these include infectious agents, sunlight, organic dusts (including flour dust, textile dust, and wood dust), mineral dusts, metals, and ionizing radiation. Nevertheless, even repeatedly observed associations (e.g., employment as farmer) have not been entirely consistent across studies. A well-defined set of occupations and potential exposures relevant to NHL etiology has yet to be established.

Among the potential reasons for the lack of consistency in previous findings is the idea that individual case–control studies lack the power to provide stable estimates of relative risk for less-common occupations and are susceptible to chance findings because of the large number of occupations evaluated. Studies differ somewhat in how occupational details are recorded, coded, analyzed, and reported, making comparison difficult, and they may not be comparable in terms of the NHL subtypes included and tumor classifications used. Finally, there may be true differences in risk associated with the same occupation across different study regions owing to local differences in population characteristics, exposure patterns, and NHL subtype distribution.

To determine the extent of agreement with previous findings in the large pooled dataset of InterLymph consortium studies, we conducted an analysis of occupations in relation to NHL using a uniform classification of occupations and NHL pathology. Our aims were a) to confirm the relationship of occupations of a priori interest to NHL and its subtypes, and b) to estimate the contribution of specific occupations of a priori interest to the incidence of NHL and its subtypes.

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