Meta-analysis of the association between cigarette smoking and incidence of Hodgkin's Lymphoma

Systematic replication of smoking disease associations using survey responses and EHR data in the All of Us Research Program

OBJECTIVE

The All of Us Research Program (All of Us) aims to recruit over a million participants to further precision medicine. Essential to the verification of biobanks is a replication of known associations to establish validity. Here, we evaluated how well All of Us data replicated known cigarette smoking associations.

MATERIALS AND METHODS

We defined smoking exposure as follows: (1) an EHR Smoking exposure that used International Classification of Disease codes; (2) participant provided information (PPI) Ever Smoking; and, (3) PPI Current Smoking, both from the lifestyle survey. We performed a phenome-wide association study (PheWAS) for each smoking exposure measurement type. For each, we compared the effect sizes derived from the PheWAS to published meta-analyses that studied cigarette smoking from PubMed. We defined two levels of replication of meta-analyses: (1) nominally replicated: which required agreement of direction of effect size, and (2) fully replicated: which required overlap of confidence intervals.

RESULTS

PheWASes with EHR Smoking, PPI Ever Smoking, and PPI Current Smoking revealed 736, 492, and 639 phenome-wide significant associations, respectively. We identified 165 meta-analyses representing 99 distinct phenotypes that could be matched to EHR phenotypes. At P < .05, 74 were nominally replicated and 55 were fully replicated. At P < 2.68 × 10-5 (Bonferroni threshold), 58 were nominally replicated and 40 were fully replicated.

DISCUSSION

Most phenotypes found in published meta-analyses associated with smoking were nominally replicated in All of Us. Both survey and EHR definitions for smoking produced similar results.

CONCLUSION

This study demonstrated the feasibility of studying common exposures using All of Us data.

Classic Hodgkin lymphoma in young people

Classic Hodgkin lymphoma (CHL) is a unique form of lymphoid cancer featuring a heterogeneous tumor microenvironment and a relative paucity of malignant Hodgkin and Reed-Sternberg (HRS) cells with characteristic phenotype. Younger individuals (children, adolescents and young adults) are affected as often as the elderly, producing a peculiar bimodal age-incidence profile that has generated immense interest in this disease and its origins. Decades of epidemiological investigations have documented the populations most susceptible and identified multiple risk factors that can be broadly categorized as either biological or environmental in nature. Most risk factors result in overt immunodeficiency or confer more subtle alterations to baseline health, physiology or immune function. Epstein Barr virus, however, is both a risk factor and well-established driver of lymphomagenesis in a significant subset of cases. Epigenetic changes, along with the accumulation of somatic driver mutations and cytogenetic abnormalities are required for the malignant transformation of germinal center-experienced HRS cell precursors. Chromosomal instability and the influence of endogenous mutational processes are critical in this regard, by impacting genes involved in key signaling pathways that promote the survival and proliferation of HRS cells and their escape from immune destruction. Here we review the principal features, known risk factors and lymphomagenic mechanisms relevant to newly diagnosed CHL, with an emphasis on those most applicable to young people.

Survival for waitlisted kidney failure patients receiving transplantation versus remaining on waiting list: systematic review and meta-analysis

OBJECTIVES

To investigate the survival benefit of transplantation versus dialysis for waitlisted kidney failure patients with a priori stratification.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Online databases MEDLINE, Ovid Embase, Web of Science, Cochrane Collection, and ClinicalTrials.gov were searched between database inception and 1 March 2021.

INCLUSION CRITERIA

All comparative studies that assessed all cause mortality for transplantation versus dialysis in patients with kidney failure waitlisted for transplant surgery were included. Two independent reviewers extracted the data and assessed the risk of bias of included studies. Meta-analysis was done using the DerSimonian-Laird random effects model, with heterogeneity investigated by subgroup analyses, sensitivity analyses, and meta-regression.

RESULTS

The search identified 48 observational studies with no randomised controlled trials (n=1 245 850 patients). In total, 92% (n=44/48) of studies reported a long term (at least one year) survival benefit associated with transplantation compared with dialysis. However, 11 of those studies identified stratums in which transplantation offered no statistically significant benefit over remaining on dialysis. In 18 studies suitable for meta-analysis, kidney transplantation showed a survival benefit (hazard ratio 0.45, 95% confidence interval 0.39 to 0.54; P<0.001), with significant heterogeneity even after subgroup/sensitivity analyses or meta-regression analysis.

CONCLUSION

Kidney transplantation remains the superior treatment modality for most patients with kidney failure to reduce all cause mortality, but some subgroups may lack a survival benefit. Given the continued scarcity of donor organs, further evidence is needed to better inform decision making for patients with kidney failure.

STUDY REGISTRATION

PROSPERO CRD42021247247.

Risk of Severe COVID-19 Increased by Metabolic Dysfunction-associated Fatty Liver Disease: A Meta-analysis

BACKGROUND

The prevalence of metabolic dysfunction-associated fatty liver disease (MAFLD) in coronavirus disease-2019 (COVID-19) patients and whether it affects the outcomes of COVID-19 requires investigation.

GOALS

The aim was to determine the prevalence of MAFLD among COVID-19 patients and its influence on the outcomes of COVID-19 by meta-analysis.

METHODS

Our study protocol has been registered on PROSPERO (CRD42021242243). The studies published on PubMed, Embase, Cochrane Library, and Web of Science before March 11, 2021 were screened. The Newcastle-Ottawa scale (NOS) and Agency for Healthcare Research and Quality scale were used to assess the quality of the studies. Pooled analysis was conducted using the software RevMan version 5.3 and Stata version 15.0 SE. The stability of the results was assessed by sensitivity analysis. Publication bias was evaluated using funnel plots, Egger test, and trim-and-fill analysis.

RESULTS

Seven studies covering 2141 COVID-19 patients were included. It was confirmed that MAFLD increased the risk of severe COVID-19 (odds ratios: 1.80, 95% confidence interval: 1.53-2.13, P<0.00001). No association was found between the presence of MAFLD and the occurrence of COVID-19 death. The pooled prevalence of MAFLD among COVID-19 patients was 36% (95% confidence interval: 0.23-0.49, P<0.00001). Sensitivity analysis confirmed that the initial results were stable.

CONCLUSIONS

MAFLD can increase the incidence of severe COVID-19, but the correlation between MAFLD and COVID-19 death has not been confirmed. Further investigation is needed to explore the possible mechanism of this association. Since MAFLD is common among patients infected with SARS-CoV-2, more care should be given to COVID-19 patients with underlying MAFLD.

Synchronous occurrence of Hurthle cell carcinoma with Hodgkin's lymphoma; the first reported case with literature review

Introduction

Hurthle cell carcinoma (HCC) is a rare type of thyroid cancer while Hodgkin's lymphoma (HL) is an uncommon cancer of the lymphocytes. The synchronous occurrence of HCC and HL in a single person has not been described in the literature. This report aims to present the first case of synchronous HCC and HL.

Case report

A 31-year-old male presented with a right side neck swelling for three months. Laboratory findings revealed elevated thyroglobulin (286.7 ng/ml). Ultrasound (US) examination showed several enlarged lymph nodes (<20mm) in the right side of the neck with increased vascularity. There was also a solitary solid thyroid nodule (23*20mm) in the right lobe. Fine needle aspiration cytology (FNAC) of the right lobe revealed Hurthle cell neoplasm, and right cervical lymph node was suspicious for Hodgkin's lymphoma. Right lobectomy with right lateral cervical excisional biopsy was performed. Histopathology confirmed HCC and HL.

Discussion

HCC is a differentiated cancer occurring in old age population. Multiple factors increase the risk of HCC, including the excess iodine, history of thyroid diseases, and exposure to radiation. HL is a cancer of the lymphatic system that affects young adults and older population. There is a significant association between excess body weight and cigarette smoking with the risk of HL.

Conclusion

Although extremely rare, occurrence of a few cases of other thyroid carcinomas and HL could occur. However, no relation has been described between the two cancers.

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Hurthle cell carcinoma is a rare, well-differentiated, and aggressive thyroid cancer.

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Hodgkin's lymphoma is a cancer of the lymphocytes, associated with good prognosis.

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This report presents the first case of synchronous Hurthle cell carcinoma and Hodgkin lymphoma.

Rotating Nightshift Work and Hematopoietic Cancer Risk in US Female Nurses

Background

Nightshift work is a plausible risk factor for hematologic cancer, but epidemiological evidence remains sparse, especially for individual subtypes. We prospectively examined the association of rotating nightshift work with hematopoietic cancer risk.

Methods

This cohort study included US women from the Nurses’ Health Study (NHS: n = 76 846, 1988–2012) and Nurses’ Health Study II (NHSII: n = 113 087, 1989–2013). Rotating nightshift work duration was assessed at baseline (both cohorts) and cumulatively updated (NHSII). Cox regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for overall hematopoietic cancer and specific histologic subtypes. All statistical tests were two-sided.

Results

We documented 1405 (NHS) and 505 (NHSII) incident hematopoietic cancer cases during follow-up. In NHS, compared with women who never worked rotating nightshifts, longer rotating nightshift work duration was associated with an increased risk of overall hematopoietic cancer (HR_1–14y = 0.93, 95% CI = 0.83 to 1.04; HR_≥15y = 1.28, 95% CI = 1.06 to 1.55; P_trend = .009). In NHSII, results were similar though not statistically significant (HR_1–14y = 0.99, 95% CI = 0.82 to 1.21; HR_≥15y = 1.41, 95% CI = 0.88 to 2.26; P_trend = .47). In the subtype analyses in the NHS, the association of history of rotating nightshift work with risk of diffuse large B-cell lymphoma varied by duration (HR_1–14y = 0.71, 95% CI = 0.51 to 0.98; HR_≥15y = 1.69, 95% CI = 1.07 to 2.67; P_trend = .01) compared with those who never worked rotating nightshifts. Women reporting a longer history of rotating nightshifts also had suggestive (statistically nonsignificant) increased risks of overall non-Hodgkin lymphoma (HR_≥15y = 1.19, 95% CI = 0.95 to 1.49), Hodgkin lymphoma (HR_≥15y = 1.32, 95% CI = 0.43 to 4.06), and multiple myeloma (HR_≥15y = 1.42, 95% CI = 0.85 to 2.39).

Conclusions

Longer duration (≥15 years) of rotating nightshift work was associated with increased risks of overall and several subtypes of hematopoietic cancer.

Long-term risk of cardiovascular mortality in lymphoma survivors: A systematic review and meta-analysis

Cardiovascular disease has been identified as one of the late complications of cancer therapy. The purpose of this study was to quantify the long-term risk of cardiovascular mortality among lymphoma survivors relative to that of the general population. A systematic review and meta-analysis were conducted. Articles were identified in November 2016 by searching EMBASE, MEDLINE, and CINAHL databases. Observational studies were included if they assessed cardiovascular mortality in patients with lymphoma who survived for at least 5 years from time of diagnosis or if they had a median follow-up of 10 years. A pooled standardized mortality ratio (SMR) was estimated using a DerSimonian and Laird random-effects model. The Q and I2 statistics were used to assess heterogeneity. Funnel plots and Begg's and Egger's tests were used to evaluate publication bias. Of the 7450 articles screened, 27 studies were included in the systematic review representing 46 829 Hodgkin and 14 764 non-Hodgkin lymphoma survivors. The pooled number of deaths attributable to cardiovascular disease among Hodgkin and non-Hodgkin disease was estimated to be 7.31 (95% CI: 5.29-10.10; I2  = 95.4%) and 5.35 (95% CI: 2.55-11.24; I2  = 94.0%) times that of the general population, respectively. This association was greater among Hodgkin lymphoma survivors treated before the age of 21 (pooled SMR = 13.43; 95% CI: 9.22-19.57; I2  = 78.9%). There was a high degree of heterogeneity and a high risk of bias due to confounding in this body of literature. Lymphoma survivors have an increased risk of fatal cardiovascular events compared to the general population and should be targeted for cardiovascular screening and prevention campaigns.

Pesticide exposure as a risk factor for myelodysplastic syndromes: a meta-analysis based on 1,942 cases and 5,359 controls

OBJECTIVE

Pesticide exposure has been linked to increased risk of cancer at several sites, but its association with risk of myelodysplastic syndromes (MDS) is still unclear. A meta-analysis of studies published through April, 2014 was performed to investigate the association of pesticide exposure with the risk of MDS.

METHODS

Studies were identified by searching the Web of Science, Cochrane Library and PubMed databases. Summary odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated using random- or fixed-effect models.

RESULTS

This meta-analysis included 11 case-control studies, all of which demonstrated a correlation between pesticide exposure and a statistically significant increased risk of MDS (OR=1.95, 95% CI 1.23-3.09). In subgroup analyses, patients with pesticide exposure had increased risk of developing MDS if they were living in the Europe or Asia and had refractory anemia (RA) or RA with ringed sideroblasts (RARS). Moreover, in the analysis by specific pesticides, increased risk was associated with exposure to insecticides (OR=1.71, 95% CI 1.22-2.40) but not exposure to herbicides or fungicides.

CONCLUSION

This meta-analysis supports the hypothesis that exposure to pesticides increases the risk of developing MDS. Further prospective cohort studies are warranted to verify the association and guide clinical practice in MDS prevention.

Tumor-associated neutrophils as a new prognostic factor in cancer: a systematic review and meta-analysis

Purpose

Tumor-associated neutrophils (TAN) have been reported in a variety of malignancies. We conducted an up-to-date meta-analysis to evaluate the prognostic role of TAN in cancer.

Method

Pubmed, Embase and web of science databases were searched for studies published up to April 2013. Pooled hazard ratios (HRs) and their corresponding 95% confidence intervals (CIs) were calculated. The impact of neutrophils localization and primary antibody were also assessed.

Results

A total of 3946 patients with various solid tumors from 20 studies were included. High density of intratumoral neutrophils were independently associated with unfavorable survival; the pooled HRs were 1.68 (95%CI: 1.36–2.07, I² = 55.8%, p<0.001) for recurrence-free survival (RFS)/disease-free survival (DFS), 3.36 (95%CI: 2.08–5.42, I² = 0%, p<0.001) for cancer-specific survival (CSS) and 1.66 (95%CI: 1.37–2.01, I² = 70.5%, p<0.001) for overall survival (OS). Peritumoral and stromal neutrophils were not statistically significantly associated with survival. When grouped by primary antibody, the pooled HRs were 1.80 (95%CI: 1.47–2.22, I² = 67.7%, p<0.001) for CD66b, and 1.44 (95%CI: 0.90–2.30, I² = 45.9%, p = 0.125) for CD15, suggesting that CD66b positive TAN might have a better prognostic value than CD15.

Conclusion

High levels of intratumoral neutrophils are associated with unfavorable recurrence-free, cancer-specific and overall survival.

Risk and prognosis of ovarian cancer in women with endometriosis: a meta-analysis

Background:

The risk and prognosis of ovarian cancer have not been well established in women with endometriosis. Thus, we investigated the impact of endometriosis on the risk and prognosis for ovarian cancer, and evaluated clinicopathologic characteristics of endometriosis-associated ovarian cancer (EAOC) in comparison with non-EAOC.

Methods:

After we searched an electronic search to identify relevant studies published online between January 1990 and December 2012, we found 20 case–control and 15 cohort studies including 444 255 patients from 1 625 potentially relevant studies. In the meta-analysis, ovarian cancer risk by endometriosis and clinicopathologic characteristics were evaluated using risk ratio (RR) or standard incidence ratio (SIR), and prognosis was investigated using hazard ratio (HR) with 95% confidence interval (CI). Heterogeneity was evaluated using Higgins I² to select fixed-effect (I² ⩽50%) or random effects models (I²>50%), and found no publication bias using funnel plots with Egger's test (P>0.05). Furthermore, we performed subgroup analyses based on study design, assessment of endometriosis, histology, disease status, quality of study and adjustment for potential confounding factors to minimise bias.

Results:

Endometriosis increased ovarian cancer risk in case–control or two-arm cohort studies (RR, 1.265; 95% CI, 1.214–1.318) and single-arm cohort studies (SIR, 1.797; 95% CI, 1.276–2.531), which were similar in subgroup analyses. Although progression-free survival was not different between EAOC and non-EAOC (HR, 1.023; 95% CI, 0.712–1.470), EAOC was associated with better overall survival than non-EAOC in crude analyses (HR, 0.778; 95% CI, 0.655–0.925). However, progression-free survival and overall survival were not different between the two groups in subgroup analyses. Stage I–II disease, grade 1 disease and nulliparity were more common in EAOC (RRs, 1.959, 1.319 and 1.327; 95% CIs, 1.367–2.807, 1.149–1.514 and 1.245–1.415), whereas probability of optimal debulking surgery was not different between the two groups (RR, 1.403; 95% CI, 0.915–2.152). Furthermore, endometrioid and clear cell carcinomas were more common in EAOC (RRs, 1.759 and 2.606; 95% CIs, 1.551–1.995 and 2.225–3.053), whereas serous carcinoma was less frequent in EAOC than in non-EAOC (RR, 0.733; 95% CI, 0.617–0.871), and there was no difference in the risk of mucinous carcinoma between the two groups (RR, 0.805; 95% CI, 0.584–1.109). These clinicopathologic characteristics were also similar in subgroup analyses.

Conclusions:

Endometriosis is strongly associated with the increased risk of ovarian cancer, and EAOC shows favourable characteristics including early-stage disease, low-grade disease and a specific histology such as endometrioid or clear cell carcinoma. However, endometriosis may not affect disease progression after the onset of ovarian cancer.

Cancer incidence in systemic sclerosis: meta-analysis of population-based cohort studies

OBJECTIVE

To examine cancer incidence in patients with systemic sclerosis (SSc) through a meta-analysis of population-based cohort studies.

METHODS

Five different databases (Medline, Scopus, CINAHL [Cumulative Index to Nursing and Allied Health Literature], Web of Science, and Cochrane Collaboration) were searched for articles published between January 1966 and May 2012; review articles and the reference lists from the articles that resulted from the search were also evaluated. Population-based cohort studies with data relevant to the determination of cancer risk in patients with SSc were included. All articles that met strict inclusion criteria were analyzed for data on population size, time of followup, and observed-to-expected cancer ratios, also known as standardized incidence ratios (SIRs).

RESULTS

Six articles met criteria and were included in the meta-analysis. The pooled SIR for the incidence of cancer overall was 1.41 (95% confidence interval [95% CI] 1.18-1.68), and significant heterogeneity was observed as a consequence of variability in the participants, outcome, study design, and risk of bias among the studies. Men had a significantly higher pooled SIR (1.85 [95% CI 1.49-2.31]) than women (SIR 1.33 [95% CI 1.18-1.49]) (P < 0.01), and stratification for sex eliminated heterogeneity, which indicates that variability among the studies greatly contributed to differences between the sexes. There were no differences between limited cutaneous SSc and diffuse cutaneous SSc (P = 0.77). Significant increases were observed in the risk of cancer of the lung, liver, hematologic system, and bladder, as well as of non-Hodgkin's lymphoma and leukemia.

CONCLUSION

SSc is associated with an increased risk of cancer, particularly lung, liver, hematologic, and bladder cancers, although absolute risk is relatively low. Men with SSc have a higher risk of developing cancer than women.

Cigarette smoking and risk of Hodgkin lymphoma and its subtypes: a pooled analysis from the International Lymphoma Epidemiology Consortium (InterLymph)

BACKGROUND

The etiology of Hodgkin lymphoma (HL) remains incompletely characterized. Studies of the association between smoking and HL have yielded ambiguous results, possibly due to differences between HL subtypes.

PATIENTS AND METHODS

Through the InterLymph Consortium, 12 case-control studies regarding cigarette smoking and HL were identified. Pooled analyses on the association between smoking and HL stratified by tumor histology and Epstein-Barr virus (EBV) status were conducted using random effects models adjusted for confounders. Analyses included 3335 HL cases and 14 278 controls.

RESULTS

Overall, 54.5% of cases and 57.4% of controls were ever cigarette smokers. Compared with never smokers, ever smokers had an odds ratio (OR) of HL of 1.10 [95% confidence interval (CI) 1.01-1.21]. This increased risk reflected associations with mixed cellularity cHL (OR = 1.60, 95% CI 1.29-1.99) and EBV-positive cHL (OR = 1.81, 95% CI 1.27-2.56) among current smokers, whereas risk of nodular sclerosis (OR = 1.09, 95% CI 0.90-1.32) and EBV-negative HL (OR = 1.02, 95% CI 0.72-1.44) was not increased.

CONCLUSION

These results support the notion of etiologic heterogeneity between HL subtypes, highlighting the need for HL stratification in future studies. Even if not relevant to all subtypes, our study emphasizes that cigarette smoking should be added to the few modifiable HL risk factors identified.

Tobacco smoking and risk of multiple myeloma: a meta-analysis of 40 observational studies

This meta-analysis aims to quantitatively synthesize all available data on the association between tobacco smoking and multiple myeloma (MM) risk. Eligible studies were identified and pooled effect estimates (odds ratios and relative risks) were calculated regarding ever, current and former smoking. Separate analyses were performed on case-control and cohort studies, as well as on males and females. Meta-regression analysis with percentage of males, mean age, years of smoking, pack-years, cigarettes per day, years since quit and age at onset was performed. Forty articles were deemed eligible; of them 27 used a case-control design (4,625 cases and 21,591 controls) and 13 used a cohort design (2,228 incident cases among a total cohort size equal to 1,852,763 subjects). Ever smoking was not associated with MM risk (pooled effect estimate = 0.92, 95% confidence interval (CI): 0.85-1.00); similar results were obtained for current (pooled effect estimate = 0.87, 95% CI: 0.74-1.03) and former smoking (pooled effect estimate = 1.04, 95% CI: 0.96-1.13). Regarding ever smoking, the null association was reproducible upon cohort studies (pooled effect estimate = 1.01, 95%CI: 0.89-1.15), whereas the inverse association in case-control studies (pooled effect estimate = 0.87, 95% CI: 0.78-0.96) was particularly due to the bias-prone hospital-based ones. Meta-regression analysis did not yield statistically significant results. In conclusion, MM does not seem to be associated with tobacco smoking. There is a need to further explore how molecular mechanisms are involved in the resistance of MM progenitor cells toward smoking.

18F-FDG-PET/CT in lymphoma: two decades of experience

The use of (18)F-FDG-PET/CT has changed the management of patients with lymphoma for the last two decades. This technique improves initial staging of the disease, making a prognostic approach and appropriate treatment planning, as well as monitoring therapy response of lymphoma. However, there are still controversial issues in medical literature that impact on daily clinical practice. This comprehensive literature review summarizes the current information regarding the potential use of (18)F-FDG-PET/CT in patients with lymphoma, highlighting the main applications and the current dilemmas for the nuclear medicine physicians at the time of the evaluation of these studies, trying to standardize criteria for its assessment, particularly in restaging and therapy monitoring.

Epidemiologic overview of malignant lymphoma

Malignant lymphoma encompasses a wide variety of distinct disease entities. It is generally more common in developed countries and less common in developing countries. The East Asia region has one of the lowest incidence rates of malignant lymphoma. The incidence of malignant lymphoma around the world has been increasing at a rate of 3-4% over the last 4 decades, while some stabilization has been observed in developed countries in recent years. The reasons behind this lymphoma epidemic are poorly understood, although improving diagnostic accuracy, the recent AIDS epidemic, an aging world population and the increasing adoption of cancer-causing behaviors are suggested as contributing factors. Etiologies of malignant lymphoma include infectious agents, immunodeficiency, autoimmune disease, exposure to certain organic chemicals, and pharmaceuticals. The distribution of many subtypes exhibit marked geographic variations. Compared to the West, T/natural killer (NK) cell lymphomas (T/NK-cell lymphoma) and extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) are relatively more common, whereas other B-cell lymphomas, particularly follicular lymphoma and chronic lymphocytic leukemia/small lymphocytic lymphoma, are less common in Asia. Some subtypes of T/NK-cell lymphomas defined by Epstein-Barr virus association are predominantly Asian diseases, if not exclusively so. Both ethnic and environmental factors play roles in such diversity. In this review, we discuss the geographic distribution and etiology of malignant lymphoma, as well as the trend.

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.