Cigarette smoking and risk of non-Hodgkin lymphoma subtypes among women

Second malignant neoplasms in lymphomas, secondary lymphomas and lymphomas in metabolic disorders/diseases

With inconsistent findings, evidence has been obtained in recent years that metabolic disorders are closely associated with the development of lymphomas. Studies and multiple analyses have been published also indicating that some solid tumor survivors develop a secondary lymphoma, whereas some lymphoma survivors subsequently develop a second malignant neoplasm (SMN), particularly solid tumors. An interaction between the multiple etiologic factors such as genetic factors and late effects of cancer therapy may play an important role contributing to the carcinogenesis in patients with metabolic diseases or with a primary cancer. In this review, we summarize the current knowledge of the multiple etiologic factors for lymphomagenesis, focusing on the SMN in lymphoma, secondary lymphomas in primary cancers, and the lymphomas associated to metabolic disorders/diseases, which have been received less attention previously. Further, we also review the data of coexistence of lymphomas and hepatocellular carcinoma (HCC) in patients with infection of hepatitis C virus and hepatitis B virus.

Hazards of Recurrence, Second Primary, or Other Tumor at Ten Years After Surgery for Non-Small-Cell Lung Cancer

INTRODUCTION

Better treatment options entail the risk of multiple tumors in a patient's lifetime. We studied the incidence, risk factors, and prognostic impact of second primaries and other malignancies in patients with operated non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

We retrospectively analyzed 342 consecutive patients with curatively resected NSCLC between 2003 and 2007.

RESULTS

Among the 342 patients analyzed, 172 (50.3%) developed locoregional and/or distant recurrence; 25 (7.3%) had a second primary lung cancer, 97 (28.3%) had 1 or more malignancies other than NSCLC either in their history (n = 61; 17.8%) or following resection (n = 64; 18.7%). One hundred fifteen patients (33.6%) had a malignancy other than primary NSCLC. Eight patients developed both a second primary lung cancer and another malignancy. Older age and lower N-stage were significantly correlated with the occurrence of an additional tumor, as shown by a logistic regression nomogram. Whereas the risk of recurrence decreases over time, the risk of developing a second tumor, particularly a second primary lung cancer, remains high during up to 10 years of follow-up. One hundred seventy patients (49.7%) died of the primary (n = 158; 46.2%) or second primary (n = 12; 3.5%) NSCLC, 23 (6.7%) died of another malignancy, and 66 (19.3%) died due to unrelated causes (overall 10-year survival, 33.3%).

CONCLUSIONS

Second primary lung cancer or other malignancy occurs in 33% of patients with NSCLC; 26% of patients are affected within 10 years after resection of lung cancer. With curative treatment of secondary tumors, there is no negative influence on long-term prognosis of NSCLC; therefore, follow-up beyond 5 years is strongly advisable.

Association between snus use over time and smoking cessation in Norwegian smokers

BACKGROUND AND AIMS

The effect of snus (Swedish moist snuff) use over time on smoking cessation has not been clearly established. This study aimed to assess whether there is an association between snus use over the life-span and smoking cessation in Norway.

DESIGN AND SETTING

Yearly national cross-sectional surveys (2007-17) among Norwegian adults.

PARTICIPANTS

A total of 5353 ever-daily smokers aged 16-79 years, 61.0% of whom (n = 3268) had quit daily smoking, and 16.9% (n = 903) were ever snus users.

MEASUREMENTS

Retrospective data on smoking and snus use initiation and smoking cessation. Cox proportional hazard models were applied to estimate the association between time from initiation of snus use and quitting smoking.

FINDINGS

There was a significant association between snus use and quitting smoking during the 5 first years after starting using snus (hazard ratio = 1.92, confidence interval = 1.62-2.26), but not thereafter.

CONCLUSION

In Norway, snus use appears to be associated with a higher likelihood of quitting smoking within the first 5 years of initiation of this use.

Impact of tobacco smoking on the risk of developing 25 different cancers in the UK: a retrospective study of 422,010 patients followed for up to 30 years

BACKGROUND

The aim of this study was to analyze the impact of tobacco smoking on the risk of developing 25 different cancers in patients followed for up to 30 years in general practices in the UK.

METHODS

This study included all individuals with at least one visit to one of 196 general practitioners' offices in the UK between January 1988 and December 2008 (index date). Only individuals with documented smoking status were included. Smokers and non-smokers were matched (1:1) by age, gender, index year, body mass index, and physician. The main outcome of the study was the risk of cancer as a function of smoking status. Data regarding a total of 25 cancers were available for the present analysis. The risk of cancer was analyzed using Cox's regression model.

RESULTS

The present retrospective study included 211,005 smokers and 211,005 non-smokers. The mean age was 36.5 years (SD = 12.5 years) in men and 34.3 years (SD = 13.1 years) in women. There was a slightly positive association between smoking and any cancer in both men (HR = 1.07) and women (HR = 1.03). Smoking was further found to be positively associated with several cancers, such as liver cancer, bladder and kidney cancers, pancreas cancer, and lymphoma. By contrast, the use of tobacco was negatively associated with the risk of developing skin cancer, prostate cancer, multiple myeloma, endometrial carcinoma, or breast cancer.

CONCLUSIONS

Smoking increased the overall risk of cancer in primary care practices in the UK. In addition, smoking was predominantly positively and less frequently negatively associated with numerous specific cancers.

Polycyclic aromatic hydrocarbons: determinants of residential carpet dust levels and risk of non-Hodgkin lymphoma

PURPOSE

To investigate the risk of non-Hodgkin lymphoma (NHL) associated with residential carpet dust measurements of polycyclic aromatic hydrocarbons (PAHs).

METHODS

We evaluated the relationship between residential carpet dust PAH concentrations (benz(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, chrysene, dibenz(a,h)anthracene, and indeno(1,2,3-c,d)pyrene, and their sum) and risk of NHL (676 cases, 511 controls) in the National Cancer Institute Surveillance Epidemiology and End Results multicenter case-control study. As a secondary aim, we investigated determinants of dust PAH concentrations. We computed odds ratios (OR) and 95 % confidence interval (CI) for associations between NHL and concentrations of individual and summed PAHs using unconditional logistic regression, adjusting for age, gender, and study center. Determinants of natural log-transformed PAHs were investigated using multivariate least-squares regression.

RESULTS

We observed some elevated risks for NHL overall and B cell lymphoma subtypes in association with quartiles or tertiles of PAH concentrations, but without a monotonic trend, and there was no association comparing the highest quartile or tertile to the lowest. In contrast, risk of T cell lymphoma was significantly increased among participants with the highest tertile of summed PAHs (OR = 3.04; 95 % CI, 1.09-8.47) and benzo(k)fluoranthene (OR = 3.20; 95 % CI, 1.13-9.11) compared with the lowest tertile. Predictors of PAH dust concentrations in homes included ambient air PAH concentrations and the proportion of developed land within 2 km of a residence. Older age, more years of education, and white race were also predictive of higher levels in homes.

CONCLUSION

Our results suggest a potential link between PAH exposure and risk of T cell lymphoma and demonstrate the importance of analyzing risk by NHL histologic type.

Exposure to environmental tobacco smoke and risk of non-Hodgkin lymphoma in nonsmoking men and women

Little is known about the risk of non-Hodgkin lymphoma (NHL) in nonsmokers who are exposed to environmental tobacco smoke (ETS). Previous research on NHL and ETS has not included men or examined doses of ETS exposure during childhood. The Cancer Prevention Study II Nutrition Cohort collected information on smoking habits and exposure to ETS during childhood and adulthood. Among 61,326 never-smoking men and women, 884 incident cases of NHL were identified between 1992 and 2009. Multivariable-adjusted relative risks and 95% confidence intervals were calculated using Cox proportional hazards regression to identify associations between ETS and NHL risk. Compared with no exposure to ETS as a child or an adult, childhood and/or adult ETS exposure was not associated with NHL overall. There was a positive association between the number of smokers in the house as a child (P for trend = 0.05) and exposure to 6 or more hours per week of ETS as an adult (relative risk = 2.37, 95% confidence interval: 1.12, 5.04) with follicular lymphoma risk. Adult ETS exposure was associated with a lower risk of diffuse large B-cell lymphoma (relative risk = 0.68, 95% confidence interval: 0.48, 0.97). This study suggests that adult and childhood ETS exposure may affect the risk of NHL, and that the associations differ by histological subtype.

Is cancer risk still reduced if you give up smoking in later life?

SUMMARY This report summarizes the experimental and epidemiological evidence examining the ability of smoking cessation to influence cancer risk reduction in later life. Available evidence suggests that smoking cessation even in later years can significantly reduce mortality and yield risk reductions for many cancers including lung, oral, head and neck, and stomach cancer, among others. More research is necessary to accurately quantify the degree of cancer risk reduction for particular age groups and to calculate the minimum time of cessation necessary to produce a significant benefit for the patient. Smoking cessation is the only approach that has been shown to effectively reduce the risk of many cancers on a mass scale. Considering this, we recommend that healthcare providers communicate these benefits to patients at every opportunity and reinforce the notion that it is never too late to quit smoking.

Current understanding of lifestyle and environmental factors and risk of non-hodgkin lymphoma: an epidemiological update

The incidence rates of non-Hodgkin lymphoma (NHL) have steadily increased over the last several decades in the United States, and the temporal trends in incidence can only be partially explained by the HIV epidemic. In 1992, an international workshop sponsored by the United States National Cancer Institute concluded that there was an “emerging epidemic” of NHL and emphasized the need to investigate the factors responsible for the increasing incidence of this disease. Over the past two decades, numerous epidemiological studies have examined the risk factors for NHL, particularly for putative environmental and lifestyle risk factors, and international consortia have been established in order to investigate rare exposures and NHL subtype-specific associations. While few consistent risk factors for NHL aside from immunosuppression and certain infectious agents have emerged, suggestive associations with several lifestyle and environmental factors have been reported in epidemiologic studies. Further, increasing evidence has suggested that the effects of these and other exposures may be limited to or stronger for particular NHL subtypes. This paper examines the progress that has been made over the last twenty years in elucidating the etiology of NHL, with a primary emphasis on lifestyle factors and environmental exposures.

Risk Factors of Follicular Lymphoma

INTRODUCTION: Non-Hodgkin Lymphoma (NHL) is a heterogeneous group of malignancies with over thirty different subtypes. Follicular lymphoma (FL) is the most common form of indolent NHL and the second most common form of NHL overall. It has morphologic, immunophenotypic and clinical features significantly different from other subtypes. Considerable effort has been devoted to the identification of risk factors for etiology and prognosis of FL. These risk factors may advance our understanding of the biology of FL and have an impact on clinical practice. AREAS COVERED: The epidemiology of NHL and FL is briefly reviewed. For FL etiology and prognosis separately, we review clinical, environmental and molecular (including genetic, genomic, epigenetic and others) risk factors suggested in the literature. EXPERT OPINION: A large number of potential risk factors have been suggested in recent studies. However, there is a lack of consensus, and many of the suggested risk factors have not been rigorously validated in independent studies. There is a need for large-scale, prospective studies to consolidate existing findings and discover new risk factors. Some of the identified risk factors are successful at the population level. More effective individual-level risk factors and models remain to be identified.

Cigarette smoking is associated with a small increase in the incidence of non-Hodgkin lymphoma: a meta-analysis of 24 observational studies

Previous studies have evaluated the association between cigarette smoking and incidence of non-Hodgkin lymphoma (NHL) with inconclusive results. Our main objective was to evaluate this relationship using a meta-analysis of observational studies. A literature search was undertaken through October 2011 looking for pertinent studies. Seven prospective cohort and 17 case-control studies were included in this meta-analysis. Outcomes were calculated using the random-effects model and are reported as odds ratio (OR). Meta-regression was used to evaluate the dose-response of intensity and duration of smoking in NHL incidence. Our study found an OR of 1.40 (95% confidence interval [CI] 1.14-1.73; p = 0.001) in current female smokers seen only in case-control studies. No increased odds of NHL was seen in men. There was no association between smoking and the most common NHL subtypes, with the exception of a statistical trend toward a higher incidence of T-cell lymphoma. In conclusion, there appears to be an increase in the odds of NHL in current female smokers.

Polymorphisms in immune function genes and non-Hodgkin lymphoma survival

INTRODUCTION

Cytokines play a critical role in regulating the immune system. In the tumor microenvironment, they influence survival, proliferation, differentiation, and movement of both tumor and stromal cells, and regulate tumor interactions with the extracellular matrix. Given these biologic properties, there is reason to hypothesize that cytokine activity influences the pathogenesis of non-Hodgkin lymphoma (NHL).

METHODS

We investigated the effect of genetic variation in cytokine genes on NHL prognosis and survival by evaluating genetic variation in individual SNPs as well as the combined effect of multiple deleterious genotypes. Survival information from 496 female incident NHL cases diagnosed during 1996-2000 in Connecticut were abstracted from Connecticut Tumor Registry in 2008. Survival analyses were conducted by comparing Kaplan-Meier curves and hazard ratios (HR) were computed using Cox proportional hazard models adjusting for demographic and tumor characteristics for genes that were suggested by previous studies to be associated with NHL survival.

RESULTS

We found that the variant IL6 genotype is significantly associated (HR = 0.42; 95%CI: 0.23-0.77) with a decreased risk of death, as well as relapse and secondary cancer occurrence, among those with NHL. We also found that risk of death, relapse, and secondary cancers varied by specific SNPs for the follicular, DLBCL, and CLL/SLL histologic types. We identified combinations of polymorphisms whose combined deleterious effect significantly alter overall NHL survival and disease-free survival.

CONCLUSION

Our study provides evidence that the identification of genetic polymorphisms in cytokine genes may help improve the prediction of NHL survival and prognosis.

Cigarette smoking, passive smoking, and non-Hodgkin lymphoma risk: evidence from the California Teachers Study

Epidemiologic studies conducted to date have shown evidence of a causal relation between smoking and non-Hodgkin lymphoma (NHL) risk. However, previous studies did not account for passive smoking exposure in the never-smoking reference group. The California Teachers Study collected information about lifetime smoking and household passive smoking exposure in 1995 and about lifetime exposure to passive smoking in 3 settings (household, workplace, and social settings) in 1997-1998. Multivariable-adjusted relative risks and 95% confidence intervals were estimated by fitting Cox proportional hazards models with follow-up through 2007. Compared with never smokers, ever smokers had a 1.11-fold (95% confidence interval (CI): 0.94, 1.30) higher NHL risk that increased to a 1.22-fold (95% CI: 0.95, 1.57) higher risk when women with household passive smoking were excluded from the reference category. Statistically significant dose responses were observed for lifetime cumulative smoking exposure (intensity and pack-years; both P 's for trend = 0.02) when women with household passive smoking were excluded from the reference category. Among never smokers, NHL risk increased with increasing lifetime exposure to passive smoking (relative risk = 1.51 (95% CI: 1.03, 2.22) for >40 years vs. ≤5 years of passive smoking; P for trend = 0.03), particularly for follicular lymphoma (relative risk = 2.89 (95% CI: 1.23, 6.80); P for trend = 0.01). The present study provides evidence that smoking and passive smoking may influence NHL etiology, particularly for follicular lymphoma.

Risk factors for non-Hodgkin lymphoma subtypes defined by histology and t(14;18) in a population-based case-control study

The t(14;18) chromosomal translocation is the most common cytogenetic abnormality in non-Hodgkin lymphoma (NHL), occurring in 70-90% of follicular lymphomas (FL) and 30-50% of diffuse large B-cell lymphomas (DLBCL). Previous t(14;18)-NHL studies have not evaluated risk factors for NHL defined by both t(14;18) status and histology. In this population-based case-control study, t(14;18) status was determined in DLBCL cases using fluorescence in situ hybridization on paraffin-embedded tumor sections. Polytomous logistic regression was used to evaluate the association between a wide variety of exposures and t(14;18)-positive (N=109) and -negative DLBCL (N=125) and FL (N=318), adjusting for sex, age, race, and study center. Taller height, more lifetime surgeries, and PCB180 exposure were associated with t(14;18)-positivity. Taller individuals (third tertile vs. first tertile) had elevated risks of t(14;18)-positive DLBCL (odds ratio [OR] = 1.8, 95% confidence interval [CI] 1.1-3.0) and FL (OR=1.4, 95%CI 1.0-1.9) but not t(14;18)-negative DLBCL. Similar patterns were seen for individuals with more lifetime surgeries (13+ vs. 0-12 surgeries; t(14;18)-positive DLBCL OR=1.4, 95%CI 0.7-2.7; FL OR=1.6, 95%CI 1.1-2.5) and individuals exposed to PCB180 greater than 20.8 ng/g (t(14;18)-positive DLBCL OR=1.3, 95%CI 0.6-2.9; FL OR=1.7, 95%CI 1.0-2.8). In contrast, termite treatment and high alpha-chlordane levels were associated with t(14;18)-negative DLBCL only, suggesting that these exposures do not act through t(14;18). Our findings suggest that putative associations between NHL and height, surgeries, and PCB180 may be t(14;18)-mediated and provide support for case-subtyping based on molecular and histologic subtypes. Future efforts should focus on pooling data to confirm and extend previous research on risk factors for t(14;18)-NHL subtypes.

Vegetable and fruit intake and non-Hodgkin lymphoma survival in Connecticut women

We investigated whether an increased intake of vegetables and fruits favors NHL survival. A cohort of 568 female cases of incident NHL diagnosed during 1996-2000 in Connecticut was followed up for a median of 7.7 years. Adjusted hazard ratios (HRs) were estimated by Cox proportional hazard models. Our results show that a pre-diagnostic high intake of vegetables appeared to favor overall survival (HR = 0.74, 95% CI 0.57-0.98) among patients with NHL who survived longer than 6 months. In particular, pre-diagnostic high intakes of green leafy vegetables and citrus fruits were associated with 29% (95% CI 0.51-0.98) and 27% (95% CI 0.54-0.99) reduced risk of death, respectively. When different types of vegetables and fruits were investigated separately, their impacts were found to vary in NHL subtypes. Our study suggests that increasing vegetable and citrus fruit consumption could be a useful strategy to improve survival in NHL patients.

A case-control study of tobacco use and other non-occupational risk factors for lymphoma subtypes defined by t(14; 18) translocations and bcl-2 expression

OBJECTIVE

We re-evaluated reported associations between tobacco use and other factors and non-Hodgkin lymphoma (NHL) t(14; 18)-subtypes based on fluorescence in situ hybridization (FISH) assays believed to be more sensitive than polymerase chain reaction (PCR), previously used for detecting t(14; 18).

METHODS

Commercial FISH assays and bcl-2 immunostaining were performed on paraffin sections to determine t(14; 18) and bcl-2 case-subtypes. Polytomous logistic regression models estimated associations between NHL case-subtypes (versus 1,245 population-based controls) and tobacco use as well as other factors.

RESULTS

Adjusting for age, state, and proxy status, t(14; 18)-negative NHL was associated with any tobacco use (vs. no tobacco use, OR = 1.9, 95% CI = 1.0-3.5), including current smoking (vs. no cigarette use, OR = 1.9, 95% CI = 1.1-3.2). Tobacco exposures were not clearly associated with t(14; 18)-positive NHL or bcl-2 case-subtypes. Hair-dye use and family history of a hemolymphatic cancer were associated with t(14; 18)-negative NHL, but the number of exposed cases was small.

CONCLUSIONS

The association between t(14; 18)-negative NHL and cigarette smoking was unexpected given previous evidence of associations between smoking and follicular lymphoma (which is largely t(14; 18)-positive). Future studies characterizing additional molecular characteristics of t(14; 18)-negative NHL may help determine whether the association with smoking may have been causal versus an artifact of chance or bias.

Risk of non-Hodgkin lymphoma and nitrate and nitrite from the diet in Connecticut women

It has been estimated that 65,980 individuals were diagnosed with non-Hodgkin lymphoma (NHL) and 19,500 died from NHL in the United States in 2009. Although established risk factors such as immunodeficiency and viral infections may be responsible for a portion of the cases, the majority of NHL cases remain unexplained. Dietary nitrate and nitrite intake are exposures of particular interest for NHL risk as they are precursors in the endogenous formation of N-nitroso compounds, which cause lymphomas in animal studies. We investigated NHL risk overall and by histologic type in relation to dietary nitrate and nitrite intake in a population-based case-control study of 1,304 women in Connecticut. Nitrate and nitrite intake were assessed using a 120-item food frequency questionnaire. We found no association between risk of NHL overall and dietary nitrate and a slightly increased risk of NHL with higher dietary nitrite intake (highest vs. lowest intake quartile OR = 1.4; 95% CI: 0.9-2.2). When we evaluated intake by subtype, a significant positive trend was observed for follicular lymphoma and nitrate (p-trend = 0.04) and nitrite (p-trend < 0.01) with an over twofold risk in the highest nitrite intake quartile (OR = 2.3; 95% CI: 1.1-4.9). An increased risk in the highest quartile of nitrite intake was also observed for T-cell lymphoma (OR = 3.4; 95% CI: 1.0-11.9). Animal products containing nitrite were more strongly associated with risk of follicular lymphoma; whereas, both animal and plant sources of nitrite were associated with elevated ORs for T-cell lymphoma. Our results confirm a previous finding for nitrite intake and NHL risk and highlight the importance of evaluating histologic type. We conclude that these results should be replicated in a larger study with data on drinking water as well as dietary sources of nitrate intake.

Genetic polymorphisms in the metabolic pathway and non-Hodgkin lymphoma survival

Metabolic pathway enzymes, such as Cytochrome P450 (CYP), glutathione S-transferase (GST), and N-acetyltransferases (NAT) are involved in activation and detoxification of environmental carcinogens as well as drug metabolism. We hypothesized that the genetic variations in such metabolic pathways may affect NHL prognosis and survival. Follow-up information of 496 female NHL incident cases diagnosed during 1996-2000 in Connecticut were abstracted from the Connecticut Tumor Registry in 2008; survival analyses were conducted by comparing the Kaplan-Meier curves, and hazard ratios (HR) were computed from the Cox Proportional Hazard models adjusting for demographic and tumor characteristics which were suggested by previous studies to be determinants of NHL survival. We identified six SNPs from four metabolism genes (CYP2E1, GSTP1, GSTT1, and NAT1) that were associated with NHL survival. Specifically, polymorphisms in GSTT1 were associated with follicular lymphoma survival; and polymorphisms in CYP2E1, GSTP1, and NAT1 were associated with survival of chronic lymphocytic leukemia/small lymphocytic lymphoma. Our study suggests that genetic polymorphisms in metabolic pathways may help improve the prediction of NHL survival and prognosis.

Genetic variation in N-acetyltransferases 1 and 2, cigarette smoking, and risk of non-Hodgkin lymphoma

Cigarette smoke contains many carcinogens that are metabolically activated through xenobiotic metabolism by phase I and II enzymes, including N-acetyltransferases 1 and 2 (NAT1 and NAT2). We investigated non-Hodgkin lymphoma risk in general and by subtype in relation to NAT1 and NAT2 genotypes and cigarette smoking in a population-based case-control study in Connecticut. Of the 535 controls, 53.1% reported ever smoking, and of the 461 cases, 55.7% reported ever smoking. We found a two-fold increased risk of T-cell lymphoma among those possessing the NAT1*10 genotype compared to those with other NAT1 genotypes; including an OR of 2.0 (95% CI: 1.0-2.4) for those heterozygous or homozygous for NAT1*10 genotypes. Rapid acetylator NAT2 phenotype increased the risk of both T-cell lymphoma (OR = 3.2; 95% CI: 1.1-9.5) and marginal zone lymphoma (OR = 3.0; 95% CI: 1.0-8.7), though these results were based on a small number of cases. When smoking status and risk of NHL was stratified by NAT1 and NAT2 genotypes, an increased risk of NHL overall was observed in current (OR = 1.7; 95% CI: 1.2-2.4) smokers without the NAT1*10 genotype but not among smokers with the NAT1*10 genotype (p-interaction < 0.01). No association between history of cigarette smoking and risk of NHL overall was observed with any NAT2 genotype. Our results present modest evidence that acetylation rate is associated with risk of NHL for specific subtypes and that the NAT1*10 genotype is an "at-risk" allele. Additionally, our results suggest that the relationship between NHL and smoking status may be modified by common genetic variation in NAT1 but not NAT2. We conclude that these findings require replication in larger studies and ultimately in pooled analyses.

Genetic polymorphisms in nitric oxide synthase genes modify the relationship between vegetable and fruit intake and risk of non-Hodgkin lymphoma

Oxidative damage caused by reactive oxygen species and other free radicals is involved in carcinogenesis. It has been suggested that high vegetable and fruit intake may reduce the risk of non-Hodgkin lymphoma (NHL) as vegetables and fruit are rich in antioxidants. The aim of this study is to evaluate the interaction of vegetable and fruit intake with genetic polymorphisms in oxidative stress pathway genes and NHL risk. This hypothesis was investigated in a population-based case-control study of NHL and NHL histologic subtypes in women from Connecticut, including 513 histologically confirmed incident cases and 591 randomly selected controls. Gene-vegetable/fruit joint effects were estimated using unconditional logistic regression model. The false discovery rate method was applied to adjust for multiple comparisons. Significant interactions with vegetable and fruit intake were mainly found for genetic polymorphisms on nitric oxide synthase (NOS) genes among those with diffuse large B-cell lymphoma and follicular lymphoma. Two single nucleotide polymorphisms in the NOS1 gene were found to significantly modify the association between total vegetable and fruit intake and risk of NHL overall, as well as the risk of follicular lymphoma. When vegetables, bean vegetables, cruciferous vegetables, green leafy vegetables, red vegetables, yellow/orange vegetables, fruit, and citrus fruits were examined separately, strong interaction effects were narrowed to vegetable intake among patients with diffuse large B-cell lymphoma. Our results suggest that genetic polymorphisms in oxidative stress pathway genes, especially in the NOS genes, modify the association between vegetable and fruit intake and risk of NHL.

Genetic polymorphisms in glutathione S-transferases and cytochrome P450s, tobacco smoking, and risk of non-Hodgkin lymphoma

We investigated variation in glutathione S-transferases (GSTs) and cytochrome P450s (CYPs), and smoking in a population-based case-control study of NHL including 1,115 women. Although risk of NHL was not altered by variant polymorphisms in GSTs or CYPs, it was significantly changed for DLBCL when considered in conjunction with smoking behavior, though only in nonsmokers. An increased risk of DLBCL in nonsmokers was associated with the variant G allele for GSTP1 (OR = 1.6, 95% CI 1.0-2.3) and CYP1A1 (OR = 2.4; 95% CI 1.0-5.7), but a decreased risk for the variant G allele for CYP1B1 (OR = 0.6, 95% CI 0.4-1.0). Our results confer support investigation of the gene-environment interaction in a larger study population of DLBCL.

The utility of t(14;18) in understanding risk factors for non-Hodgkin lymphoma

Characteristic chromosomal abnormalities are associated with specific histological subtypes of non-Hodgkin lymphoma (NHL). The chromosomal translocation t(14;18)(q32;q21) is one of the most common chromosomal abnormalities in NHL, occurring in 70%-90% of cases of follicular lymphoma, 20%-30% of diffuse large B-cell lymphoma, and 5%-10% of other less common subtypes. The t(14;18)-positive NHL may represent a homogenous group and, consequently, increase etiologic specificity in epidemiological studies. Although the t(14;18) has important clinical ramifications, its etiologic significance remains to be determined. Two population-based, case-control studies addressed this issue by evaluating potential risk factors for t(14;18)-positive and t(14;18)-negative subgroups of NHL. Both studies found that the association between pesticide exposures and risk of NHL was largely limited to t(14;18)-positive NHL cases. However, the findings regarding cigarette smoking, family history of hematopoietic cancer, and hair dye use were not entirely consistent. These results indicate that defining subgroups of NHL according to t(14;18) status may be useful for etiologic research, particularly for exposures that are genotoxic or may contribute to the development of NHL through pathways involving the t(14;18). Studies to further evaluate these associations and delineate the effects of various exposures in other genetically defined subgroups of NHL are warranted.

Case-control study of lymphoid neoplasm in three French areas: description, alcohol and tobacco consumption

A multi-centre hospital-based case-control study was conducted in three regions of France between 2000 and 2003 in order to establish the risk factors of lymphoid neoplasms. We report here results concerning alcohol and tobacco consumption. A total of 298 cases and 276 controls, case-matched by inclusion centre, age and sex were included. Cases were classified according to the World Health Organization classification and validated by an expert panel of eight pathologists. Overall alcohol intake did not incur any risk increase for non-Hodgkin's lymphoma. Wine consumption marginally increased the risk of follicular lymphoma [odds ratio=2.19 (0.83-5.80)], with a higher risk for drinkers who started before the age of 20 years [odds ratio=4.04 (1.19-13.76)] and for drinkers who consumed more than 19 g of alcohol per day [odds ratio=4.37 (1.04-18.45)]. Beer and spirit consumption was not linked to non-Hodgkin's lymphoma risk. Tobacco consumption did not show a risk increase. The risk increase of follicular lymphoma due to wine consumption was new. We discuss this risk based on the French context, France being the European country with the highest alcohol consumption, particularly of wine.

The non-Hodgkin lymphomas: a review of the epidemiologic literature

The non-Hodgkin lymphomas (NHL) are a heterogeneous group of B-cell and T-cell neoplasms that arise primarily in the lymph nodes. NHL incidence rates in the US doubled between about 1970 and 1990, and stabilized during the 1990s. NHL accounts for approximately 3.4% of cancer deaths in the US. Although some of the observed patterns in NHL have been related to HIV/AIDS, these conditions cannot fully explain the magnitude of the changes; neither do changes in classification systems nor improved diagnostic capabilities. Studies of occupational and environmental exposures (e.g., pesticides, solvents) have produced no consistent pattern of significant positive associations. Inverse associations with ultraviolet radiation exposure and alcohol and fish intake, and positive associations with meat and saturated fat intake have been reported in several studies; additional studies are needed to confirm or refute these associations. Family history of NHL or other hematolympho-proliferative cancers and personal history of several autoimmune disorders are associated with increased risk of NHL, but are not likely to account for a large proportion of cases. HIV and other infectious agents, such as human herpesvirus 8 and Epstein-Barr, appear to be associated with differing types of NHL, such as some B-cell lymphomas. Future epidemiologic studies should evaluate associations by NHL type, enhance exposure information collected, and elucidate factors that may identify susceptible (or resistant) subpopulations because of genetic, immunologic or other characteristics. The extent to which the etiology of NHL types may differ is important to resolve in ongoing and future studies.

Risk of second malignant neoplasms among lymphoma patients with a family history of cancer

Radiotherapy and chemotherapy are known risk factors for second cancers after lymphoma. The role of genetic influences, however, remains largely unknown. We assessed risk of second cancers associated with family history of any cancer in 41,181 patients with Hodgkin lymphoma (HL) (n = 7,476), non-Hodgkin lymphoma (NHL) (n = 25,941), or chronic lymphocytic leukemia (CLL) (n = 7,764), using a large population-based database. Family history of cancer was based on a diagnosis of any cancer in 110,862 first-degree relatives. We found increased relative risk (RR) (1.81, 95% confidence interval (CI): 1.04-3.16) of breast cancer among HL patient with positive (vs. negative) family history of cancer. Among CLL patients with positive (vs. negative) family history of cancer, we observed elevated risks of bladder (RR = 3.53, 95% CI: 1.31-9.55) and prostate cancer (RR = 2.15, 95% CI: 1.17-3.94). For NHL patients with positive (vs. negative) family history of cancer, we observed non-significantly increased risk of non-melanoma skin cancer (RR = 1.94, 95% CI: 0.86-4.38) and lung cancer (RR = 1.99, 95% CI: 0.73-5.39). Our observations suggest that genetic factors, as measured by positive family history of cancer, may be influential risk-factors for selected second tumors following lymphoproliferative disorders.

Genetic polymorphisms in the oxidative stress pathway and susceptibility to non-Hodgkin lymphoma

Oxidative damage caused by reactive oxygen species (ROS) and other free radicals is involved in a number of pathological conditions including cancer. In a population-based case-control study of non-Hodgkin lymphoma (NHL) (n = 518 cases, 597 controls) among women in Connecticut, we analyzed one or more single nucleotide polymorphisms (SNPs) in ten candidate genes (AKR1A1, AKR1C1, AKR1C3, CYBA, GPX1, MPO, NOS2A, NOS3, OGG1, and SOD2) that mediate oxidative stress directly or indirectly in the NADPH oxidase-dependent respiratory burst. Odds ratios (OR) and 95% confidence intervals (CI) were adjusted for age and race. Polymorphisms in AKR1A1 and CYBA were significantly associated with increased risk of NHL. There was a 1.7-fold (95% CI = 1.2-2.4, P = 0.0047) increased risk of NHL for individuals who were variant homozygous for the AKR1A1 (IVS5 + 282T > C) SNP. The effect was most pronounced for risk of diffuse large B-cell lymphoma, but risk estimates were non-significantly elevated for other common B-cell histologies and T-cell lymphomas as well. In addition, individuals variant homozygous for the CYBA (Ex4 + 11C > T) SNP had a 1.6-fold (95% CI = 1.1-2.4, P = 0.019) increased risk of NHL that was particularly pronounced for T-cell lymphoma (OR = 3.5, 95% CI = 1.3-9.6, P = 0.013), but was also associated with non-significant increased risks for each of the common B-cell histologies. These results suggest that SNPs in genes related to the oxidative stress pathway may be associated with increased risk of NHL.

Epidemiology and etiology of non-Hodgkin lymphoma--a review

The etiology of non-Hodgkin lymphoma, as well as its global dramatic rise in incidence during the past decades, remains largely unexplained. However, there is increasing awareness that this group of malignancies may entail not only clinical, morphological and molecular heterogeneity, but also considerable variations in terms of etiologic factors. In this review, epidemiologic patterns are summarized as well as current evidence of associations between various known or suspected risk factors for non-Hodgkin lymphoma overall or for any of its subtypes. Central pathogenetic mechanisms include immunosuppression, especially in relation to T-cell function and loss of control of latent EBV infection, and chronic antigen stimulation. Some degree of familiar aggregation also implies a role for genetic susceptibility. A number of recent investigations of non-Hodgkin lymphoma etiology will hopefully lead to a better understanding of the causes of these malignancies.

Expression of DNA mismatch repair proteins in transformed non-Hodgkin's lymphoma: relationship to smoking

It has been hypothesized that defects in DNA-mismatch repair are associated with smoking in certain types of transformed non-Hodgkin lymphoma (NHL). We have analyzed biopsy samples from two indolent B-cell lymphomas, follicular lymphoma (FL) and chronic lymphocytic leukemia/small lymphocytic leukemia (CLL/SLL), that have transformed to diffuse-large B-cell lymphoma (DLBCL). We correlated the presence or absence of DNA-mismatch repair enzymes by immunostaining as well as the p53 status to smoking history. Of all patients (n = 30), 37% showed negative immunostaining of MLH1, 16% showed negative immunostaining of MSH2 and 63% had p53 mutations and/or protein expression. Eighteen out of 20 transformed follicular lymphomas and seven out of 10 CLL/SLL that have transformed to DLBCL (Richter's syndrome) were informative for smoking histories. We found that the relative risk of negative immunostaining for either MLH1 or MSH2 was 2.2 times higher in smokers than non-smokers (relative risk = 2.2041, 95% confidence interval: 0.89714, 5.41491). No direct correlation was found between smoking and the mutations in the p53 gene. These results suggest that cigarette smoking may play a role in the development of transformed lymphomas through defective mismatch repair.

Tobacco use, body mass index and the risk of malignant lymphomas--a nationwide cohort study in Sweden

In the search for risk factors involved in the etiology of lymphoproliferative malignancies there is still inconsistent evidence regarding effects of smoking tobacco, and the role of smokeless tobacco is poorly investigated. New evidence indicates that excess body weight increases the risk of NHL and HD. To determine if tobacco use of various forms and high Body Mass Index (BMI) affect the occurrence of these neoplasms, we conducted a prospective cohort study on over 330,000 Swedish construction workers included in the Construction Industry Working Environment and Health program. Information on smoking, snuff dipping, height and weight was gathered by self administered questionnaires together with personal interviews. Cancer incidence was ascertained through the year 2000 by record linkage to the nationwide Swedish Cancer Registry, Migration Registry and Cause of Death Registry. At the end of follow up, 1,309 subjects had been diagnosed with NHL (including chronic lymphocytic leukemia) and 205 with HD respectively. Age adjusted incidence rate ratios were computed using Cox proportional Hazard regression modeling. Smoking cigarette, pipe or cigar was not associated with NHL or HD. There was no evidence indicating a relation between quantity and duration of smoking and NHL or HD risk. No link was found between NHL and usage of smokeless tobacco. Having a BMI of 30 or higher did not convey excess risk of developing NHL or HD compared to normal weight (BMI 18.6-24.9). We conclude that tobacco smoking and high BMI do not entail an increased risk of NHL and HD. Our findings of a relation between the duration of snuff dipping and HD need further investigation.

Cytokine polymorphisms in the Th1/Th2 pathway and susceptibility to non-Hodgkin lymphoma

Studies have demonstrated that common polymorphisms in Th1 and Th2 cytokine genes can alter gene expression, modulate the balance between Th1/Th2 responsiveness, and influence susceptibility for autoimmune disorders, infectious diseases, and cancer. We analyzed one or more single nucleotide polymorphisms (SNPs) in 20 candidate Th1/Th2 genes in a population-based case-control study of non-Hodgkin lymphoma (NHL; n = 518 cases, 597 controls) among women in Connecticut. SNPs in critical genes, IL4, IL5, IL6, and IL10, were associated with risk for NHL and in some instances with a specific histologic subtype. Analysis of 4 SNPs in the IL10 promoter (-3575T>A, -1082A>G, -819C>T, and -592C>A) revealed that both the AGCC haplotype (odds ratio [OR] = 1.54, 95% confidence interval [CI] = 1.21-1.96, P < .001) and the TATA haplotype (OR = 1.37, 95% CI = 1.05-1.79, P = .02) were associated with increased risk for B-cell lymphomas. In contrast, the IL4-1098G allele was associated with increased risk of T-cell lymphomas (OR = 3.84; 95% CI = 1.79-8.22; P < .001). Further, the IL10 and IL4 SNP associations remained significant after adjusting for multiple comparisons. These results suggest that SNPs in Th2 cytokine genes may be associated with risk of NHL.

Tobacco and alcohol consumption and risk of lymphoma: Results of apopulation-based case-control study in Germany

Changing trends in lifestyle exposures are suggested to be contributing factors to the increasing incidence rates for lymphoma. We investigated the relationship between smoking and alcohol consumption and the risk of lymphoma among adult participants of a population-based case-control study recently conducted in Germany. In 710 case-control pairs, an increased risk of lymphoma was associated with a long duration of smoking (p for trend = 0.01 for men) and smoking of > 20 cigarettes per day(OR = 2.7; 95% CI = 1.4-5.2 for women). Elevated odds ratios were seen for most lymphoma subentities, albeit mostly without reaching statistical significance. A strong association was evident between smoking and multiple myeloma (OR = 2.4, 95% CI = 0.98-5.74 for men; OR = 2.9, 95% CI = 1.1-7.4 for women) and Hodgkin's lymphoma among men (OR = 3.6; 95% CI = 1.7-7.5). Alcohol consumption 10 years prior to the date of interview appeared to decrease the risk of lymphoma. Odds ratios for men who reported alcohol consumption were 53% lower (95% CI = 0.31-0.71) compared to men who drank very little or no alcohol. The same tendency was evident for women, although the association was less pronounced. The inverse relationship was also seen for low amounts of alcohol and did not appear to be restricted to specific types of beverages. Although biologic rationale for a protective effect of alcohol consumption may be given, a more in-depth analysis involving genetic markers is indicated to clarify if ethanol, other components in alcoholic beverages, or factors associated with moderate drinking reduce lymphoma risk among adults. In conclusion, this investigation suggests a positive association between tobacco smoking and lymphoma risk and finds decreased odds ratios among consumers of alcohol.

Tobacco smoking, alcohol drinking and non-Hodgkin's lymphoma: A European multicenter case-control study (Epilymph)

To study the role of tobacco smoking and alcohol drinking in the etiology of non-Hodgkin's lymphoma (NHL), we conducted a multicenter case-control study in Spain, France, Germany, Italy, Ireland and Czech Republic between 1998 and 2004, which included 1,742 cases of NHL and 2,465 controls matched on age, sex and recruitment area. Tobacco smoking was not associated with the risk of NHL overall or with risk of specific histological subtypes. Similarly, there was no association between alcohol drinking and the risk of NHL overall or across histological subtypes. However, a protective effect of alcohol drinking was observed among men (OR = 0.76, 95% CI = 0.62-0.93) and in non-Mediterranean countries (OR = 0.73, 95% CI = 0.61-0.86). There was no evidence of interaction between alcohol drinking and tobacco smoking in NHL etiology. The results of this large-scale European study did not support an association between tobacco and NHL and suggested a protective effect of alcohol on development of NHL for men and in non-Mediterranean countries.

Tobacco use and non-Hodgkin lymphoma: results from a population-based case-control study in the San Francisco Bay Area, California

OBJECTIVE

Investigate the association between tobacco use and non-Hodgkin lymphoma (NHL).

METHODS

Tobacco-use data were collected during in-person interviews in a population-based case-control study of NHL (N=1593 patients, N=2515 controls) conducted in the San Francisco Bay Area between 1988 and 1995. Odds ratios (ORs) for HIV-negative participants were obtained from adjusted unconditional logistic regression models stratified by sex.

RESULTS

NHL was not associated with overall tobacco use, intensity or duration of cigarette smoking in women or men. However, ORs were increased for NHL among men who used any non-cigarette tobacco alone (OR=1.7), non-cigarette tobacco and cigarettes (OR=1.4), multiple types of non-cigarette tobacco alone (OR=2.1) and smokeless tobacco alone (OR=4.0). In analyses stratified by sex and age, ORs for NHL associated with cigarette smoking in general were above unity among those aged > or =60 years. ORs for follicular lymphoma were increased in men who used cigarettes and other tobacco, cigars alone and smokeless tobacco alone. Diffuse large-cell lymphoma in men was associated with use of cigarettes and other tobacco, and multiple types of non-cigarette tobacco.

CONCLUSION

Our data do not support an association between overall tobacco use and all NHL in women or men. Further analyses are warranted in larger studies to evaluate non-cigarette tobacco use, tobacco-related biologic markers and genetic factors in the development of NHL.

Cigarette smoking and risk of non-Hodgkin's lymphoma--a population-based case-control study

BACKGROUND

Epidemiologic evidence of an association between tobacco smoking and non-Hodgkin's lymphoma has been conflicting. This may reflect that non-Hodgkin's lymphoma comprises several distinct disease entities with different etiologies, as some studies have indicated an association between smoking and follicular lymphoma.

OBJECTIVE

To investigate the association between cigarette smoking and non-Hodgkin's lymphoma risk, overall and by subtype.

METHODS

As part of a nationwide Danish-Swedish population-based case-control study, we interviewed 3,055 incident non-Hodgkin's lymphoma patients and 3,187 population controls. All lymphomas were uniformly classified according to the WHO classification. We used unconditional logistic regression to estimate adjusted odds ratios (OR) and 95% confidence intervals (95% CI) for the association between cigarette smoking and risk of non-Hodgkin's lymphoma.

RESULTS

Cigarette smoking was not associated with the risk of non-Hodgkin's lymphoma overall (OR, 0.97; 95% CI, 0.87-1.08) nor with the major subgroups such as diffuse large B-cell lymphoma (OR, 0.94; 95% CI, 0.79-1.10), chronic lymphocytic leukemia (OR, 0.86; 95% CI, 0.72-1.02), or follicular lymphoma (OR, 1.03; 95% CI, 0.85-1.24). Female smokers were at a marginally increased risk of follicular lymphoma (OR, 1.41; 95% CI, 1.04-1.92). Men who had ever smoked had a significantly increased risk of T-cell lymphoma (OR, 1.67; 95% CI, 1.11-2.51). No dose-response association with cigarette smoking could be established for any lymphoma subgroup.

CONCLUSION

We found little evidence of an association between cigarette smoking and non-Hodgkin's lymphoma risk overall. Although increased risks of follicular lymphoma in female smokers and of T-cell lymphoma in male smokers were suggested, no dose-response relationship was observed, leaving limited support for causality.

Second primary cancers among 109 000 cases of non-Hodgkin's lymphoma

An analysis of other primary cancers in individuals with non-Hodgkin's lymphoma (NHL) can help to elucidate this cancer aetiology. In all, 109 451 first primary NHL were included in a pooled analysis of 13 cancer registries. The observed numbers of second cancers were compared to the expected numbers derived from the age-, sex-, calendar period- and registry-specific incidence rates. We also calculated the standardised incidence ratios for NHL as a second primary after other cancers. There was a 47% (95% confidence interval 43–51%) overall increase in the risk of a primary cancer after NHL. A strongly significant (P<0.001) increase was observed for cancers of the lip, tongue, oropharynx^*, stomach, small intestine, colon^*, liver, nasal cavity^*, lung, soft tissues^*, skin melanoma^*, nonmelanoma skin^*, bladder^*, kidney^*, thyroid^*, Hodgkin's lymphoma^*, lymphoid leukaemia^* and myeloid leukaemia. Non-Hodgkin's lymphoma as a second primary was increased after cancers marked with an asterisk. Patterns of risk indicate a treatment effect for lung, bladder, stomach, Hodgkin's lymphoma and myeloid leukaemia. Common risk factors may be involved for cancers of the lung, bladder, nasal cavity and for soft tissues, such as pesticides. Bidirectional effects for several cancer sites of potential viral origin argue strongly for a role for immune suppression in NHL.

Follicular lymphoma: time for a re-think?

Follicular lymphoma (FL) is a malignancy of follicle centre B cells that have at least a partially follicular pattern, and is the commonest type of indolent Non-Hodgkin's lymphoma. Except in the subset of patients with localized disease, FL should still be regarded as an incurable malignancy with a relentless relapsing/remitting course. However, the provocative new data covered by this review (including anti-CD20 antibody therapy, BCL-2, radioimmunotherapy, new chemotherapeutic agents and anti-idiotype vaccination), provides much cause for excitement and guarded optimism. Rituximab represents a novel treatment approach for a variety of disease settings, with a proven excellent efficacy and toxicity profile. Long-term data is required to establish whether its use translates into survival benefit. As the clinical activity of rituximab and other new therapeutic approaches becomes established, it will be important to determine how best to integrate these results into the standard care of patients with follicular lymphoma.

Smoking and non‐Hodgkin lymphoma: Case‐control study in Italy

Tobacco smoking is a well-documented risk factor for several cancers, but the role of cigarette smoking in the etiology of non-Hodgkin lymphoma (NHL) is inadequately understood. Hepatitis C virus (HCV) has been associated with NHL, but the interaction between HCV and smoking habits has not yet been studied. Between 1999 and 2002, we conducted a case-control study on the association of HCV, smoking habits and NHL in 2 areas of northern and southern Italy. Cases were 225 consecutive patients (median age, 59 years) with a new diagnosis of NHL that were admitted to reference and general hospitals. Controls were 504 patients (median age, 63 years) admitted to the same hospitals as cases, for a wide spectrum of acute, nonneoplastic, nonimmune-, nor tobacco-related conditions. Current, heavy smokers (> or = 20 cigarettes/day) had an odds ratio (OR) of NHL of 2.10 (95% confidence interval, CI: 1.07-4.12) compared to never smokers. The association between smoking and NHL was consistent across strata of sex and age. Compared to never smokers, current smokers of > or = 20 cigarettes/day had ORs of 1.14 (95% CI: 0.37-3.56) for B-cell-low-grade, 2.10 (95% CI: 0.94-4.67) for B-cell-intermediate and high-grade, and 25.84 (95% CI: 1.95-342.17) for T-cell NHL. The effect of tobacco smoking and HCV were independent on the relative risk, leading a 4-fold elevated risk in current smokers HCV positive subjects. Tobacco smoking and hepatitis C virus (HCV) have been associated to non-Hodgkin lymphoma (NHL), but the interaction between HCV and smoking habits has not yet been studied. Our study confirms that tobacco is related to NHL, and reports on the combined effect of tobacco smoking and HCV. Infection acted together according to a multiplicative model, leading to a 4-fold elevated risk in current smokers HCV positive subjects.

Cigarette Smoking and Risk of Non-Hodgkin Lymphoma: A Pooled Analysis from the International Lymphoma Epidemiology Consortium (InterLymph)

BACKGROUND

The International Lymphoma Epidemiology Consortium (InterLymph) provides an opportunity to analyze the relationship between cigarette smoking and non-Hodgkin lymphoma with sufficient statistical power to consider non-Hodgkin lymphoma subtype. The results from previous studies of this relationship have been inconsistent, likely due to the small sample sizes that arose from stratification by disease subtype. To clarify the role of cigarette smoking in the etiology of non-Hodgkin lymphoma, we conducted a pooled analysis of original patient data from nine case-control studies of non-Hodgkin lymphoma conducted in the United States, Europe, and Australia.

METHODS

Original data were obtained from each study and uniformly coded. Risk estimates from fixed-effects and two-stage random-effects models were compared to determine the impact of interstudy heterogeneity. Odds ratios (OR) and 95% confidence intervals (95% CI) were derived from unconditional logistic regression models, controlling for study center, age, sex, and race.

RESULTS

In our pooled study population of 6,594 cases and 8,892 controls, smoking was associated with slightly increased risk estimates (OR, 1.07; 95% CI, 1.00-1.15). Stratification by non-Hodgkin lymphoma subtype revealed that the most consistent association between cigarette smoking and non-Hodgkin lymphoma was observed among follicular lymphomas (n = 1452). Compared with nonsmokers, current smokers had a higher OR for follicular lymphoma (1.31; 95% CI, 1.12-1.52) than former smokers (1.06; 95% CI, 0.93-1.22). Current heavy smoking (> or = 36 pack-years) was associated with a 45% increased OR for follicular lymphoma (1.45; 95% CI, 1.15-1.82) compared with nonsmokers.

CONCLUSIONS

Cigarette smoking may increase the risk of developing follicular lymphoma but does not seem to affect risk of the other non-Hodgkin lymphoma subtypes we examined. Future research is needed to determine the biological mechanism responsible for our subtype-specific results.