Ultraviolet radiation and incidence of non-Hodgkin's lymphoma among Hispanics in the United States

County level incidence rates of chronic lymphocytic leukemia are associated with residential radon levels

Aim:

We previously reported that incidence rates for chronic lymphocytic leukemia (CLL) among US states are significantly correlated with levels of residential radon (RR). Because these correlations could be influenced by confounding and/or misclassification among large geographic units, we reinvestigated them using smaller geographic units that better reflect exposure and disease at the individual level.

Methods:

We examined the relationships between CLL and RR per county in 478 counties with publicly-available data.

Results:

After adjustment for ultraviolet radiation, a possible risk factor for CLL, county rates for CLL and RR were significantly correlated among males and females both together and separately (p < 0.0001).

Conclusion:

CLL is significantly associated with RR at the county level.

Perinatal light imprinting of circadian clocks and systems (PLICCS): A signature of photoperiod around birth on circadian system stability and association with cancer

Recent findings from animal models suggest that plasticity of human circadian clocks and systems may be differentially affected by different paradigms of perinatal photoperiod exposure to the detriment of health in later life, including cancer development. Focusing on the example of cancer, we carry out a series of systematic literature reviews concerning perinatal light imprinting of circadian clocks and systems (PLICCS) in animal models, and concerning the risk of cancer development with the primary determinants of the perinatal photoperiod, namely season of birth or latitude of birth. The results from these systematic reviews provide supporting evidence of the PLICCS and cancer rationale and highlight that investigations of PLICCS in humans are warranted. Overall, we discuss findings from experimental research and insights from epidemiological studies. Considerations as to how to "test" PLICCS in epidemiological studies and as to the potential for non-invasive preventative measures during perinatal periods close our synthesis. If the PLICCS rationale holds true, it opens the exciting prospect for amenable, early-life, preventative measures against cancer development (and other disorders) in later life. Indeed, non-invasive anthropogenic light exposure may have enormous potential to alleviate the public health and economic burden of circadian-related diseases.

Tea extracts protect normal lymphocytes but not leukemia cells from UV radiation-induced ROS production: An EPR spin trap study

PURPOSE

An ex vivo method for detection of free radicals and their neutralization by aqueous tea in human normal lymphocytes and MEC-1 leukemia cells under ultraviolet (UV) irradiation was investigated.

MATERIALS AND METHODS

This method is based on the electron paramagnetic resonance (EPR) spectroscopy spin-trapping technique. 5-tert-butoxycarbonyl 5-methyl-1-pyrroline N-oxide (BMPO) was used as the spin trap. Normal human lymphocytes and leukemia cells were exposed to UVB radiation (290-315 nm) at 47.7 and 159 mJ/cm(2) and to UVA radiation (315-400 nm) at 53.7 J/cm(2).

RESULTS

No significant radical production at 47.7 mJ/cm(2) UVB dose in both cell lines was observed. In normal cells, free radical production was observed at 159 mJ/cm(2) UVB and 53.7 J/cm(2) UVA doses. However, both UV sources did not significantly produce free radicals in leukemia cells. A radical scavenging property of tea extracts (black, green, sage, rosehip) was observed in normal lymphocytes after both UVB and UVA exposure. In leukemia cells, the intensities of EPR signals produced in BMPO with tea extracts were found to be increased substantially after UVA exposure.

CONCLUSION

These results showed that UV radiation induced free radical formation in normal human lymphocytes and indicated that tea extracts may be useful as photoprotective agents for them. On the other hand, tea extracts facilitated free radical production in leukemia cells.

Increased incidence of malignant melanoma and other rare cutaneous cancers in the setting of chronic lymphocytic leukemia

BACKGROUND

Patients with chronic lymphocytic leukemia (CLL), small lymphocytic lymphoma (SLL), or non-Hodgkin lymphoma (NHL) are at increased risk for the development of skin malignancies.

OBJECTIVES

This study was conducted to estimate the incidences of rare skin malignancies in patients with CLL/SLL or NHL.

METHODS

Patients with a diagnosis of CLL/SLL or NHL recorded in the Surveillance, Epidemiology and End Results (SEER) database during 1992-2007 were identified. Diagnoses of specific skin malignancies were identified from SEER files.

RESULTS

During 1992-2007, a total of 128,674 patients with first diagnoses of CLL/SLL or NHL were recorded in SEER; 4743 were excluded because follow-up data were unavailable. Among the remaining 123,931 patients, 28,964 had CLL/SLL and 94,967 had NHL. Standardized incidence ratios (SIRs) for invasive malignant melanoma, Merkel cell carcinoma, malignant fibrous histiocytoma, dermatofibrosarcoma protuberans, Kaposi's sarcoma, and sebaceous carcinoma were 2.3, 8.2, 3.6, 2.5, 2.9, and 1.4, respectively, in CLL/SLL patients and 1.6, 3.2, 1.5, 1.3, 17.6, and 0.8, respectively, in NHL patients. When invasive melanoma was stratified by patient age and sex, the highest SIR (17.8) was found in men aged 0-49 years with CLL (P < 0.001).

CONCLUSIONS

Patients with CLL/SLL or NHL have a higher risk for the subsequent development of rare skin cancers. Given the more aggressive nature of these malignancies in this setting, regular monitoring for the development and prompt treatment of cutaneous malignancy is prudent in patients with NHL and particularly in patients with CLL. Regular use of sun protection may decrease the morbidity associated with skin cancer in this immunosuppressed population.

Relationship between ambient ultraviolet radiation and non-Hodgkin lymphoma subtypes: a U.S. population-based study of racial and ethnic groups

Associations between ultraviolet radiation (UVR) exposure and non-Hodgkin lymphoma (NHL) have been inconsistent, but few studies have examined these associations for specific subtypes or across race/ethnicities. We evaluated the relationship between ambient UVR exposure and subtype-specific NHL incidence for whites, Hispanics and blacks in the United States for years 2001-2010 (n = 187,778 cases). Incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were calculated for UVR quintiles using Poisson regression. Incidence was lower for the highest UVR quintile for chronic/small lymphocytic/leukemia (CLL/SLL) (IRR = 0.87, 95% CI: 0.77-0.97), mantle cell (IRR = 0.82, 95% CI: 0.69-0.97), lymphoplasmacytic (IRR = 0.58, 95% CI: 0.42-0.80), mucosa-associated lymphoid tissue (MZLMALT) (IRR = 0.74, 95% CI: 0.60-0.90), follicular (FL) (IRR = 0.76, 95% CI: 0.68-0.86), diffuse large B-cell (IRR = 0.84, 95% CI: 0.76-0.94;), peripheral T-cell other (PTCL) (IRR = 0.76, 95% CI: 0.61-0.95) and PTCL not otherwise specified (PNOS) (IRR = 0.77, 95% CI: 0.61-0.98). Trends were significant for MZLMALT, FL, DLBCL, BNOS and PTCL, with FL and DLBCL still significant after Bonferroni correction. We found interaction by race/ethnicity for CLL/SLL, FL, Burkitt, PNOS and MF/SS, with CLL/SLL and FL still significant after Bonferroni correction. Some B-cell lymphomas (CLL/SLL, FL and Burkitt) suggested significant inverse relationships in whites and Hispanics, but not in blacks. Some T-cell lymphomas suggested the most reduced risk for the highest quintile of UVR among blacks (PNOS and MF/SS), though trends were not significant. These findings strengthen the case for an inverse association of UVR exposure, support modest heterogeneity between NHL subtypes and suggest some differences by race/ethnicity.

Latitude gradients for lymphoid neoplasm subtypes in Australia support an association with ultraviolet radiation exposure

Given the uncertainty surrounding solar ultraviolet radiation (UVR) exposure and risk of lymphoid neoplasms, we performed an ecological analysis of national Australian data for incident cases diagnosed between 2002 and 2006. Subtype-specific incidence was examined by latitude band (<29°S, 29-36°S, ≥37°S), a proxy for ambient UVR exposure, using multiple Poisson regression, adjusted for sex, age-group and calendar year. Incidence increased with distance from the equator for several mature B-cell non-Hodgkin lymphomas, including diffuse large B-cell [incidence rate ratio (IRR) = 1.37; 95% confidence interval (CI): 1.16-1.61 for latitude ≥37°S relative to <29°S], lymphoplasmacytic (IRR = 1.34; 95% CI: 1.12-1.61), mucosa-associated lymphoid tissue (IRR = 1.32; 95% CI: 0.97-1.80) and mantle cell lymphoma (IRR = 1.29; 95% CI: 1.05-1.58), as well as plasmacytoma (IRR = 1.52; 95% CI: 1.09-2.11) and plasma cell myeloma (IRR = 1.15; 95% CI: 1.03-1.27). A similar pattern was observed for several mature cutaneous T-cell neoplasms, including primary cutaneous anaplastic large cell lymphoma (IRR = 4.26; 95% CI: 1.85-9.84), mycosis fungoides/Sézary syndrome (IRR = 1.72; 95% CI: 1.20-2.46), and peripheral T-cell lymphoma not otherwise specified (NOS) (IRR = 1.53; 95% CI: 1.17-2.00). Incidence of mixed cellularity/lymphocyte-depleted (IRR = 1.60; 95% CI: 1.16-2.20) and nodular sclerosis Hodgkin lymphoma (IRR = 1.57; 95% CI: 1.33-1.85) also increased with distance from the equator. Many of these subtypes have a known association with infection or immune dysregulation. Our findings support a possible protective effect of UVR exposure on the risk of several lymphoid neoplasms, possibly through vitamin D-related immune modulation critical in lymphomagenesis.

Individual, environmental, and meteorological predictors of daily personal ultraviolet radiation exposure measurements in a United States cohort study

BACKGROUND

Individual exposure to ultraviolet radiation (UVR) is challenging to measure, particularly for diseases with substantial latency periods between first exposure and diagnosis of outcome, such as cancer. To guide the choice of surrogates for long-term UVR exposure in epidemiologic studies, we assessed how well stable sun-related individual characteristics and environmental/meteorological factors predicted daily personal UVR exposure measurements.

METHODS

We evaluated 123 United States Radiologic Technologists subjects who wore personal UVR dosimeters for 8 hours daily for up to 7 days (N = 837 days). Potential predictors of personal UVR derived from a self-administered questionnaire, and public databases that provided daily estimates of ambient UVR and weather conditions. Factors potentially related to personal UVR exposure were tested individually and in a model including all significant variables.

RESULTS

The strongest predictors of daily personal UVR exposure in the full model were ambient UVR, latitude, daily rainfall, and skin reaction to prolonged sunlight (R(2) = 0.30). In a model containing only environmental and meteorological variables, ambient UVR, latitude, and daily rainfall were the strongest predictors of daily personal UVR exposure (R(2) = 0.25).

CONCLUSIONS

In the absence of feasible measures of individual longitudinal sun exposure history, stable personal characteristics, ambient UVR, and weather parameters may help estimate long-term personal UVR exposure.

Sunlight, vitamin D and the prevention of cancer: a systematic review of epidemiological studies

The number of studies reporting beneficial effects of sunlight and vitamin D on several types of cancer with a high mortality rate is growing rapidly. Present health recommendations on sun exposure are mainly based on the increased risks for skin cancer. We reviewed all published studies concerning cancer and sun exposure and vitamin D, respectively, excluding those about skin cancer. Most identified ecological, case-control and prospective studies on the incidence and mortality of colorectal, prostate, breast carcinoma and non-Hodgkin lymphoma reported a significantly inverse association with sun exposure. The results of the included studies on the association between cancer risk and vitamin D were much less consistent. Only those studies that prospectively examined the 25-hydroxyvitamin D serum levels in relation to risk of colorectal cancer are homogeneous: they all reported inverse associations, although not all reaching statistical significance. The results of the intervention studies are suggestive of a protective role of high doses of vitamin D in cancer, but they have been criticized in the literature. We, therefore, conclude that there is accumulating evidence for sunlight as a protective factor for several types of cancer. The same conclusion can be made concerning high vitamin D levels and the risk of colorectal cancer. This evidence, however, is not conclusive, because the number of (good quality) studies is still limited and publication biases cannot be excluded. The discrepancies between the epidemiological evidence for a possible preventive effect of sunlight and vitamin D and the question of how to apply the findings on the beneficial effects of sunlight to (public) health recommendations are discussed.

Prospective study of ultraviolet radiation exposure and risk of cancer in the United States

Ecologic studies have reported that solar ultraviolet radiation (UVR) exposure is associated with cancer; however, little evidence is available from prospective studies. We aimed to assess the association between an objective measure of ambient UVR exposure and risk of total and site-specific cancer in a large, regionally diverse cohort [450,934 white, non-Hispanic subjects (50-71 years) in the prospective National Institutes of Health (NIH)-AARP Diet and Health Study] after accounting for individual-level confounding risk factors. Estimated erythemal UVR exposure from satellite Total Ozone Mapping Spectrometer (TOMS) data from NASA was linked to the US Census Bureau 2000 census tract (centroid) of baseline residence for each subject. We used Cox proportional hazards models adjusted for multiple potential confounders to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for quartiles of UVR exposure. Restricted cubic splines examined nonlinear relationships. Over 9 years of follow-up, UVR exposure was inversely associated with total cancer risk (N = 75,917; highest versus lowest quartile; HR = 0.97, 95% CI = 0.95-0.99; p-trend < 0.001). In site-specific cancer analyses, UVR exposure was associated with increased melanoma risk (highest versus lowest quartile; HR = 1.22, 95% CI = 1.13-1.32; p-trend < 0.001) and decreased risk of non-Hodgkin's lymphoma (HR = 0.82, 95% CI = 0.74-0.92) and colon (HR = 0.88, 95% CI = 0.82-0.96), squamous cell lung (HR = 0.86, 95% CI = 0.75-0.98), pleural (HR = 0.57, 95% CI = 0.38-0.84), prostate (HR = 0.91, 95% CI = 0.88-0.95), kidney (HR = 0.83, 95% CI = 0.73-0.94) and bladder (HR = 0.88, 95% CI = 0.81-0.96) cancers (all p-trend < 0.05). We also found nonlinear associations for some cancer sites, including the thyroid and pancreas. Our results add to mounting evidence for the influential role of UVR exposure on cancer.

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.

Ultraviolet exposure and non-Hodgkin's lymphoma: beneficial and adverse effects?

Studies of risk of non-Hodgkin's lymphoma have found both direct and inverse correlations with respect to solar ultraviolet (UV) doses. Reduced risk is generally found in midlatitudes, while increased risk is generally found at higher latitudes. It is suggested that reduced risk arises from vitamin D production from UVB irradiance, while increased risk arises from immunosuppression associated with UVA irradiance. The ratio of UVA to UVB increases with increasing latitude.

Designs for the combination of group- and individual-level data

BACKGROUND

Studies of ecologic or aggregate data suffer from a broad range of biases when scientific interest lies with individual-level associations. To overcome these biases, epidemiologists can choose from a range of designs that combine these group-level data with individual-level data. The individual-level data provide information to identify, evaluate, and control bias, whereas the group-level data are often readily accessible and provide gains in efficiency and power. Within this context, the literature on developing models, particularly multilevel models, is well-established, but little work has been published to help researchers choose among competing designs and plan additional data collection.

METHODS

We review recently proposed "combined" group- and individual-level designs and methods that collect and analyze data at 2 levels of aggregation. These include aggregate data designs, hierarchical related regression, two-phase designs, and hybrid designs for ecologic inference.

RESULTS

The various methods differ in (i) the data elements available at the group and individual levels and (ii) the statistical techniques used to combine the 2 data sources. Implementing these techniques requires care, and it may often be simpler to ignore the group-level data once the individual-level data are collected. A simulation study, based on birth-weight data from North Carolina, is used to illustrate the benefit of incorporating group-level information.

CONCLUSIONS

Our focus is on settings where there are individual-level data to supplement readily accessible group-level data. In this context, no single design is ideal. Choosing which design to adopt depends primarily on the model of interest and the nature of the available group-level data.

Induction of B-cell lymphoma by UVB radiation in p53 haploinsufficient mice

BACKGROUND

The incidence of non-Hodgkin's lymphoma has increased over recent years. The exact etiology of lymphoma remains unknown. Ultraviolet light exposure has been associated with the development of internal lymphoid malignancies and some reports suggest that it may play a role in the development of lymphoma in humans. Here we describe the characterization and progression of lymphoma in p53 heterozygous mice exposed to UVB irradiation.

METHODS

UVB-irradiated p53+/- mice developed enlargement of the spleen. Isolated spleen cells were transplanted into Rag deficient hosts. The UV-induced tumor cells were analyzed by flow cytometry. The tumor cells were tagged with GFP to study their metastatic potential. SKY and karyotypic analysis were carried out for the detection of chromosomal abnormalities. Functional assays included in vitro class switch recombination assay, immunoglobulin rearrangement assay, as well as cytokine profiling.

RESULTS

UVB-exposed mice showed enlargement of the spleen and lymph nodes. Cells transplanted into Rag deficient mice developed aggressive tumors that infiltrated the lymph nodes, the spleen and the bone marrow. The tumor cells did not grow in immune competent syngeneic C57Bl/6 mice yet showed a modest growth in UV-irradiated B6 mice. Phenotypic analysis of these tumor cells revealed these cells are positive for B cell markers CD19+, CD5+, B220+, IgM+ and negative for T cell, NK or dendritic cell markers. The UV-induced tumor cells underwent robust in vitro immunoglobulin class switch recombination in response to lipopolysaccharide. Cytogenetic analysis revealed a t(14;19) translocation and trisomy of chromosome 6. These tumor cells secret IL-10, which can promote tumor growth and cause systemic immunosuppression.

CONCLUSION

UV-irradiated p53+/- mice developed lymphoid tumors that corresponded to a mature B cell lymphoma. Our results suggest that an indirect mechanism is involved in the development of internal tumors after chronic exposure to UV light. The induction of B cell lymphoma in UV-irradiated p53 heterozygous mice may provide a useful model for lymphoma development in humans.

Serum 25-hydroxyvitamin D and cancer mortality in the NHANES III study (1988-2006)

Vitamin D has been hypothesized to protect against cancer. We followed 16,819 participants in NHANES III (Third National Health and Nutritional Examination Survey) from 1988 to 2006, expanding on an earlier NHANES III study (1988-2000). Using Cox proportional hazards regression models, we examined risk related to baseline serum 25-hydroxyvitamin D [25(OH)D] for total cancer mortality, in both sexes, and by racial/ethnic groups, as well as for site-specific cancers. Because serum was collected in the south in cooler months and in the north in warmer months, we examined associations by collection season ("summer/higher latitude" and "winter/lower latitude"). We identified 884 cancer deaths during 225,212 person-years. Overall cancer mortality risks were unrelated to baseline 25(OH)D status in both season/latitude groups, and in non-Hispanic whites, non-Hispanic blacks, and Mexican-Americans. In men, risks were elevated at higher levels {e.g., for ≥100 nmol/L, relative risk (RR) = 1.85 [95% confidence interval (CI), 1.02-3.35] compared with <37.5 nmol/L}. Although risks were unrelated to 25(OH)D in all women combined, risks significantly decreased with increasing 25(OH)D in the summer/higher latitude group [for ≥100 nmol/L, RR = 0.52 (95% CI, 0.25-1.15) compared with <37.5 nmol/L; P(trend) = 0.03, based on continuous values]. We also observed a suggestion of an inverse association with colorectal cancer mortality (P(trend) = 0.09) and a positive association with lung cancer mortality among males (P(trend) = 0.03). Our results do not support the hypothesis that 25(OH)D is associated with reduced cancer mortality. Although cancer mortality in females was inversely associated with 25(OH)D in the summer/higher latitude group, cancer mortality at some sites was increased among men with higher 25(OH)D. These findings argue for caution before increasing 25(OH)D levels to prevent cancer.

Circulating 25-hydroxyvitamin D and risk of non-hodgkin lymphoma: Cohort Consortium Vitamin D Pooling Project of Rarer Cancers

Case-control studies generally suggesting an inverse association between sun exposure and non-Hodgkin lymphoma (NHL) have led to speculation that vitamin D may protect against lymphomagenesis. To examine this hypothesis, the authors conducted a pooled investigation of circulating 25-hydroxyvitamin D (25(OH)D) and subsequent NHL risk within 10 cohorts participating in the Cohort Consortium Vitamin D Pooling Project of Rarer Cancers. The authors analyzed measurements from 1,353 cases and 1,778 controls using conditional logistic regression and other methods to estimate the association of 25(OH)D with NHL. No clear evidence of association between categories of 25(OH)D concentration and NHL was observed overall (P(trend) = 0.68) or by sex (men, P(trend) = 0.50; women, P(trend) = 0.16). Findings for other measures (continuous log(25(OH)D), categories of 25(OH)D using sex-/cohort-/season-specific quartiles as cutpoints, categories of season-adjusted residuals of predicted 25(OH)D using quartiles as cutpoints) were generally null, although some measures of increasing 25(OH)D were suggestive of an increased risk for women. Results from stratified analyses and investigations of histologic subtypes of NHL were also null. These findings do not support the hypothesis that elevated circulating 25(OH)D concentration is associated with a reduced risk of NHL. Future research investigating the biologic basis for the sunlight-NHL association should consider alternative mechanisms, such as immunologic effects.

An ecological study of cancer mortality rates in the United States with respect to solar ultraviolet-B doses, smoking, alcohol consumption and urban/rural residence

The Cohort Consortium Vitamin D Polling Project of Rarer Cancers (VDPP ) study failed to find a beneficial role of prediagnostic serum 25-hydroxyvitamin D [25(OH)D] levels on risk of seven types of rarer cancer: endometrial, esophageal, gastric, kidney, ovarian and pancreatic cancer and non-Hodgkin's lymphoma (NHL). However, ecological studies and studies of oral vitamin D intake have generally found solar ultraviolet B (UVB) and oral vitamin D inversely correlated with incidence and/or mortality rates of these cancers. To explore the discrepancy, I conducted an ecological study of cancer mortality rates for white Americans in the United States for 1950-1994 with data for 503 state economic areas in multiple linear regression analyses with respect to UVB for July, lung cancer, alcohol consumption and urban/rural residence. UVB was significantly inversely correlated with six types of cancer (not pancreatic cancer) in both periods. However, the adjusted R(2) values were much lower for cancers with lower mortality rates than those in an earlier ecological study that used state-averaged data. This finding suggests that the VDPP study may have had too few cases. Thus, the VDPP study should not be considered as providing strong evidence against the solar UVB-vitamin D-cancer hypothesis.

Ecological studies of ultraviolet B, vitamin D and cancer since 2000

PURPOSE

The purpose of this review is to summarize ecological studies of solar ultraviolet B (UVB), vitamin D and cancer since 2000.

METHODS

The journal literature is surveyed and summarized.

RESULTS

The ecological approach has been the primary tool used during the past two decades to extend the applicability of the UVB-vitamin D-cancer theory to include at least 18 types of cancer. Many of these studies were conducted in the United States, which has the advantages of availability of reliable age-standardized cancer incidence and mortality rate data for geographic areas at various spatial resolutions, and an asymmetric solar UVB dose pattern, with higher UVB irradiance in the west and lower in the east, at any particular latitude. In addition, indices for other cancer risk-modifying factors are readily available including those for smoking, alcohol consumption, ethnic background, urban/rural residence, socioeconomic status, air pollution, and in limited fashion, diet. The ecological approach has also been used to identify latitudinal variations in cancer mortality rates in Australia, China, Japan, and Spain, and in multicountry studies. It has been used to investigate the relative roles of solar UVB and dietary factors on a global scale. The ecological approach has also been applied to cancer survival. Studies in Norway and England found that individuals diagnosed with cancer in summer or fall, when serum 25-hydroxyvitamin D levels are highest, had a milder clinical course and longer survival than those diagnosed in winter or spring.

CONCLUSION

These findings provide strong evidence that vitamin D status plays an important role in controlling the outcome of cancer. Support for the UVB-vitamin D-cancer theory is now scientifically strong enough to warrant use of vitamin D in cancer prevention, and as a component of treatment. More research studies would help to explore whether there are benefits beyond the substantial effects that have been observed.

Genetic and environmental risk indicators in canine non-Hodgkin's lymphomas: breed associations and geographic distribution of 608 cases diagnosed throughout France over 1 year

BACKGROUND

The etiology of non-Hodgkin's lymphomas (NHL) is multifactorial. Environmental and genetic factors are frequently incriminated both in humans and dogs.

OBJECTIVES

Our purpose was to study the geographic distribution of canine NHL (CNHL) in France and to evaluate genetic and environmental influences.

ANIMALS

Six hundred and eight cases of CNHL, diagnosed throughout France over 1 year, were collected from 7 Veterinary Histopathologic Laboratories.

METHODS

Retrospective study. Breeds affected by lymphomas were compared with the national population and associations between breed and immunophenotype were studied. The distribution of CNHL and canine T-cell NHL per 100,000 dogs per department was compared with the distribution of waste incinerators, polluted sites, and radioactive waste.

RESULTS

The breeds significantly overrepresented among lymphoma cases were Boxer, Setter, and Cocker Spaniel (P < .001). There was a significant association between Boxer and T-cell NHL (P < .001), and between German Shepherd and Rottweiler and B-cell NHL (P < .01). The geographic distribution of CNHL and canine T-cell NHL indicated significant heterogeneity. Significant association between distributions of CNHL and waste incinerators (rho= 0.25, P < .05), polluted sites (rho= 0.36, P < .001), and radioactive waste (rho= 0.51, P < .001) was found.

CONCLUSIONS AND CLINICAL IMPORTANCE

Influence of genetics in the development of CNHL was supported by the existence of an association between breed and immunophenotype. Waste incinerators, polluted sites, and radioactive waste could just be considered as risk indicators of CNHL, but not as risk factors. Case-control studies around critical sites are necessary to confirm the implication of those environmental factors in the development of CNHL.

How strong is the evidence that solar ultraviolet B and vitamin D reduce the risk of cancer?: An examination using Hill's criteria for causality

The ultraviolet-B (UVB)-vitamin D-cancer hypothesis was proposed in 1980. Since then, several ecological and observational studies have examined the hypothesis, in addition to one good randomized, controlled trial. Also, the mechanisms whereby vitamin D reduces the risk of cancer have been elucidated. This report aims to examine the evidence to date with respect to the criteria for causality in a biological system first proposed by Robert Koch and later systematized by A. Bradford Hill. The criteria of most relevance are strength of association, consistency, biological gradient, plausibility/mechanisms and experimental verification. Results for several cancers generally satisfy these criteria. Results for breast and colorectal cancer satisfy the criteria best, but there is also good evidence that other cancers do as well, including bladder, esophageal, gallbladder, gastric, ovarian, rectal, renal and uterine corpus cancer, as well as Hodgkin's and non-Hodgkin's lymphoma. Several cancers have mixed findings with respect to UVB and/or vitamin D, including pancreatic and prostate cancer and melanoma. Even for these, the benefit of vitamin D seems reasonably strong. Although ecological and observational studies are not generally regarded as able to provide convincing evidence of causality, the fact that humanity has always existed with vitamin D from solar UVB irradiance means that there is a wealth of evidence to be harvested using the ecological and observational approaches. Nonetheless, additional randomized, controlled trials are warranted to further examine the link between vitamin D and cancer incidence, survival and mortality.

Geographic-based ecological correlation studies using supplemental case-control data

It is well known that the ecological study design suffers from a variety of biases that render the interpretation of its results difficult. Despite its limitations, however, the ecological study design is still widely used in a range of disciplines. The only solution to the ecological inference problem is to supplement the aggregate data with individual-level data and, to this end, Haneuse and Wakefield (Biometrics 2007; 63:128-136) recently proposed a hybrid study design in which an ecological study is supplemented with a sample of case-control data. The latter provides the basis for the control of bias, while the former may provide efficiency gains. Building on that work, we illustrate the use of the hybrid design in the context of a geographical correlation study of lung cancer mortality from the state of Ohio. Focusing on epidemiological applications, we initially provide an overview of the use of ecological studies in scientific research, highlighting the breadth of current application as well as advantages and drawbacks of the design. We consider the interplay between the two sources of information in the design: ecological and case-control, and then provide details on a Bayesian spatial random effects model in the setting of the hybrid design. Issues of specification are addressed, as well as sensitivity to modeling assumptions. Further, an interesting feature of these data is that they provide an example of how the proposed design may be used to resolve the ecological fallacy.

Exposure to ultraviolet radiation and risk of malignant lymphoma and multiple myeloma--a multicentre European case-control study

BACKGROUND

Three recent studies have reported a decreased risk of non-Hodgkin lymphoma (NHL) for high ultraviolet (UV) radiation exposure.

METHODS

We conducted a multicentre case-control study during 1998-2004 in France, Germany, Ireland, Italy and Spain, comprising 1518 cases of NHL, 268 cases of Hodgkin lymphoma, 242 cases of multiple myeloma and 2124 population or hospital controls. We collected information on sensitivity to sun and personal exposure to UV radiation in childhood and adulthood via interview, and assessed occupational exposure to UV radiation from the occupational history.

RESULTS

The risk of Hodgkin and NHL was increased for increasing skin sensitivity to the sun [odds ratio (OR) for no suntan vs very brown 2.35, 95% CI 0.94-5.87 and 1.39, 95% CI 1.03-1.87, respectively]. The risk of diffuse large B-cell lymphoma was reduced for increasing adult personal (OR for highest vs lowest quartile of exposure in free days 0.62, 95% CI 0.44-0.87) and for occupational exposure to UV radiation (OR for highest vs lowest exposure tertile 0.63, 95% CI 0.37-1.04). The risk of multiple myeloma was increased for personal exposure to UV radiation during adulthood (OR for highest vs lowest quartile of exposure in free days 1.49, 95% CI 0.88-2.50). A protective effect was observed for use of sun lamps for diffuse large B-cell lymphoma (OR for 25+ times vs never 0.63, 95% CI 0.38-1.03).

CONCLUSIONS

The hypothesis of a protective effect of UV radiation on lymphoma is supported by our results. The underlying mechanisms might differ from those operating in skin carcinogenesis. The increased risk of multiple myeloma is worth replication.

UV radiation exposure, skin type and lymphoid malignancies: results of a French case-control study

OBJECTIVES

Investigating the relationship between skin type, UV exposure, and lymphoid malignancies (LM).

METHODS

We conducted a hospital-based case-control study in France, including 813 incident cases of non-Hodgkin's lymphoma (NHL), Hodgkin's lymphoma (HL), lymphoproliferative syndrome (LPS) or multiple myeloma and 748 controls.

RESULTS

Positive associations between HL and blond/red hair (OR = 1.8 [0.8-3.8]), very fair/fair skin (OR = 1.6 [1.0-2.5]) were observed. High propensity to burn was associated with HL (OR = 1.5 [1.0-2.2]) and LPS (OR = 1.4 [1.0-2.1]). Poor ability to tan was significantly associated with HL (OR = 1.7 [1.0-2.8]). Having light hair with high propensity to burn was associated with NHL (OR = 1.5 [0.9-2.5]) and significantly with HL (OR = 3.4 [1.4-8.4]). Having dark hair with high propensity to burn was significantly associated with LPS (OR = 1.5 [1.0-2.2]). The associations with HL and NHL were significant for men only, with significant interactions. Outdoors activities since leaving school or in the last decade were not related to LM. Only an almost negative trend was observed. Prior exposure to artificial UV was not associated with LM.

CONCLUSION

These results suggest a positive association between the most reactive and palest skin types and NHL or HL in men and do not rule out a slight negative relationship between UV exposure and LM.

Prospective study of serum vitamin D and cancer mortality in the United States

BACKGROUND

Vitamin D has been hypothesized to reduce cancer mortality through its effects on incidence and/or survival. Epidemiologic studies of the association of 25-hydroxyvitamin D [25(OH)D] and the risk of cancer, however, have been largely limited to incident cancers at a few sites.

METHODS

A total of 16,818 participants in the Third National Health and Nutrition Examination Survey who were 17 years or older at enrollment were followed from 1988-1994 through 2000. Levels of serum 25(OH)D were measured at baseline by radioimmunoassay. Cox proportional hazards regression models were used to examine the relationship between serum 25(OH)D levels and total cancer mortality (in the entire population or according to race/ethnicity, sex, age, and retinol status) and mortality from specific cancers. Because serum was collected in the south in cooler months and the north in warmer months, we examined associations by collection season. All statistical tests were two-sided.

RESULTS

We identified 536 cancer deaths in 146,578 person-years. Total cancer mortality was unrelated to baseline vitamin D status in the entire population, men, women, non-Hispanic whites, non-Hispanic blacks, Mexican Americans, and in persons younger than 70 or 70 years or older. We found no interaction between vitamin D and season or vitamin D and serum retinol. Colorectal cancer mortality was inversely related to serum 25(OH)D level, with levels 80 nmol/L or higher associated with a 72% risk reduction (95% confidence interval = 32% to 89%) compared with lower than 50 nmol/L, P(trend) = .02.

CONCLUSIONS

Our results do not support an association between 25(OH)D and total cancer mortality, although there was an inverse relationship between 25(OH)D levels and colorectal cancer mortality.

Sun exposure, birth weight, and childhood lymphomas: a case control study in Greece

OBJECTIVES

To explore whether the inverse association of sun exposure with non Hodgkin lymphoma among adults is also evident among the childhood population and test the specificity of the relation by contrasting the findings to those for Hodgkin lymphoma.

METHODS

A total of 87 cases of childhood (0-14 years) with non Hodgkin lymphoma and 71 with Hodgkin lymphoma, diagnosed in Greece through the national network of childhood Hematology-Oncology Units, during a 7-year period, along with 164 age- and gender-matched control children were enrolled in the study. The guardians of all eligible children were interviewed in person on the basis of a structured questionnaire covering socio-demographic, anthropometric, and perinatal characteristics. Average time of sunbathing per year at a seaside resort was used as a proxy variable of exposure to sun controlling for use of sun protection measures.

RESULTS

The estimated incidence of 10.2 cases per 1,000,000 children-years {95% Confidence Intervals (CI), 8.4-12.1} for NHL during the study period in Greece is around the average figure in countries of the European Union. There was an inverse association of sun exposure with Non Hodgkin lymphoma, namely, for an increment of 15 days of sunbathing at seaside resorts children had almost 40% lower risk (Odds Ratio: 0.60, 95% CI: 0.43-0.83), whereas no such association was evident for Hodgkin lymphoma. The risk for non Hodgkin lymphoma has been found to be statistically and significantly higher in birth weight (Odds ratio: 1.42 and 95% CI, 1.04-1.92, for every 500 g increment), whereas there was no substantial indication that maternal education or maternal smoking during the child's life were important risk factors for the disease.

CONCLUSIONS

This is the first study to provide epidemiological evidence that increased sun exposure of children may also be associated with a decreased risk of developing childhood non Hodgkin, but not Hodgkin lymphoma.

Sun exposure, vitamin D receptor gene polymorphisms and risk of non-Hodgkin lymphoma

OBJECTIVE

Recent findings suggest that ultraviolet (UV) radiation exposure may reduce risk of developing non-Hodgkin lymphoma (NHL), but the biologic basis for this relationship remains unclear. We analyzed data from our US population-based case-control study of NHL to investigate whether our previously reported inverse association with sun exposure was dependent upon variants in the vitamin D receptor gene (IVS10 + 283G > A (BsmI), Ex11 + 32T > C (TaqI)), and genes linked to UV-induced immune modulation (IL4, IL10, IL12A, IL12B, TNF).

METHODS

UV exposure data was collected from an in-person interview with 551 cases and 462 controls. We calculated odds ratios (OR) and 95% confidence intervals (CI) for sun exposure measures for joint variant-exposure effects.

RESULTS

The association with NHL risk for time in the midday sun within the last decade was dependent upon Ex11 + 32 T > C genotype. Compared to TT carriers who reported < 7 h/week of sun exposure, CC subjects with < 7 h/week of sun exposure had an increased risk of NHL (OR = 1.9, 95% CI 0.8-4.4, P(interaction) = 0.16), while the relative risks for other CC carriers approached unity with increasing level of sun exposure. This pattern of effects was especially apparent for follicular lymphoma (for CC genotype and < 7 h/week of exposure: OR 6.3, 95% CI 1.9-22, P(interaction) = 0.004), and was consistently observed across measures of reported sun exposure for different periods of life. As IVS10 + 283G > A is correlated with Ex11 + 32T > C in our population (r (2) = 0.95), results were equivalent for those with the IVS10 + 283 AA genotype. No evidence of interaction with cytokine gene variants was observed.

CONCLUSIONS

Our results suggest that the inverse association between UV exposure and NHL risk may be mediated by the vitamin D pathway. Further investigation of this finding in other studies is warranted.

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.

Latitude and incidence of ocular melanoma

We investigated the associations between latitude and the incidence of two different types of ocular melanoma, external ocular melanoma (exposed to sunlight) and internal melanoma (not exposed to sunlight), separately. Using 1992-2002 data from the Surveillance, Epidemiology, and End Results (SEER) Program of National Cancer Institute, we identified 2142 ocular melanoma cases in non-Hispanic whites, and then regressed the incidences of various types of ocular melanomas with latitude. Our analysis indicated that the higher the latitude (away from the equator, the less sun exposure), the lower the risk of external ocular melanoma (eyelid and conjunctival melanomas) among non-Hispanic whites (P for trend = 0.018). The incidence increased 2.48 fold from 47-48 degrees to 20-22 degrees. This trend is very similar to that of skin melanoma. The incidence of internal ocular melanoma (uveal melanoma) increased significantly with increasing latitudes (the less sun exposure, P for trend < 0.0001), it increased 4.91 fold from 20-22 degrees to 47-48 degrees. The latitudinal patterns of ocular melanomas may reflect the dual effects of sunlight exposure, i.e. a mutagenic effect of direct solar radiation on external ocular melanomas and a protective effect for internal uveal melanoma, which is similar to the sun radiation protective effects for various internal malignant tumors that are not exposed to the sunlight.

Sun exposure and malignant lymphoma: A population-based case–control study in Germany

Although some causes for malignant lymphoma are known their etiology is not well understood so far. We analyze the relationship between sun exposure and malignant lymphoma in a multicenter, population-based case-control study. Patients with malignant lymphoma (n = 710, 18-80 years) were prospectively recruited in 6 study regions in Germany. For each case, a gender, region and age-matched control was drawn from population-registers. In personal interviews, lifetime holidays spent in sunny climate, outdoor leisure activities and sunbed or sunlamp use were recorded. On basis of job task-specific supplementary questionnaires, an occupational physician assessed the cumulative working time outside. Odds ratios (OR) and 95%-confidence-intervals (CI) were calculated using conditional logistic regression analysis, adjusted for smoking and alcohol consumption. To increase statistical power, patients with specific lymphoma subentities were additionally compared with the entire control group using unconditional logistic regression. We observed a reduced overall lymphoma risk among subjects having spent vacations at sunny climates or frequently used sunbeds or sunlamps. The analysis of lymphoma subentities revealed similar results with the exception of T-NHL and follicular lymphoma which were positively associated with outdoor leisure activities. While cumulative working time outside appeared unrelated to NHL overall and most subentities, it was negatively associated with follicular lymphoma and weakly positively to HL. This data suggest that exposure to natural and artificial ultraviolet radiation may reduce the OR for lymphoma in this study population.

Solar ultraviolet-B exposure and cancer incidence and mortality in the United States, 1993-2002

Background

An inverse relationship between solar ultraviolet-B (UV-B) exposure and non-skin cancer mortality has long been reported. Vitamin D, acquired primarily through exposure to the sun via the skin, is believed to inhibit tumor development and growth and reduce mortality for certain cancers.

Methods

We extend the analysis of this relationship to include cancer incidence as well as mortality, using higher quality and higher resolution data sets than have typically been available. Over three million incident cancer cases between 1998 and 2002 and three million cancer deaths between 1993 and 2002 in the continental United States were regressed against daily satellite-measured solar UV-B levels, adjusting for numerous confounders. Relative risks of reduced solar UV-B exposure were calculated for thirty-two different cancer sites.

Results

For non-Hispanic whites, an inverse relationship between solar UV-B exposure and cancer incidence and mortality was observed for ten sites: bladder, colon, Hodgkin lymphoma, myeloma, other biliary, prostate, rectum, stomach, uterus, and vulva. Weaker evidence of an inverse relationship was observed for six sites: breast, kidney, leukemia, non-Hodgkin lymphoma, pancreas, and small intestine. For three sites, inverse relationships were seen that varied markedly by sex: esophagus (stronger in males than females), gallbladder (stronger in females than males), and thyroid (only seen in females). No association was found for bone and joint, brain, larynx, liver, nasal cavity, ovary, soft tissue, male thyroid, and miscellaneous cancers. A positive association between solar UV-B exposure and cancer mortality and incidence was found for anus, cervix, oral cavity, melanoma, and other non-epithelial skin cancer.

Conclusion

This paper adds to the mounting evidence for the influential role of solar UV-B exposure on cancer, particularly for some of the less-well studied digestive cancers. The relative risks for cancer incidence are similar to those for cancer mortality for most sites. For several sites (breast, colon, rectum, esophagus, other biliary, vulva), the relative risks of mortality are higher, possibly suggesting that the maintenance of adequate vitamin D levels is more critical for limiting tumor progression than for preventing tumor onset. Our findings are generally consistent with the published literature, and include three cancer sites not previously linked with solar UV-B exposure, to our knowledge: leukemia, small intestine, and vulva.

Ultraviolet radiation, dietary vitamin D, and risk of non-Hodgkin lymphoma (United States)

OBJECTIVE

Because of conflicting findings about the relationship between ultraviolet (UV) radiation and the risk of non-Hodgkin lymphoma (NHL), we evaluated the risk of several indicators related to UV, including two not previously studied: dietary vitamin D, and ambient UV levels by residential location.

METHODS

As part of a case-control study conducted in four Surveillance, Epidemiology, and End Results (SEER) registries, we collected UV information from a self-administered questionnaire and computer-assisted personal interview with 551 NHL cases and 462 controls. We estimated the relative risk (RR) and 95% confidence intervals (CI) from unconditional logistic regression models.

RESULTS

Eye color, a marker of host susceptibility to UV, showed a decreasing risk gradient for lightest eyes (0.47) compared to darkest. Relative risks were in the range of 0.73-0.78 for participants reporting more hours in the mid-day summer sun. Use of sunlamps or tanning booths was associated with decreased risk (RR = 0.88), as was estimated overall ambient UV (RR = 0.76 per 50 RB-units) overall. Vitamin D intake from diet and supplements was not related to risk. Results were thus consistent for the various indicators, although some estimated risks were not statistically significant. Effects were generally similar for diffuse large B-cell (DLBCL) and follicular lymphomas.

CONCLUSION

These data suggest a slight protective effect of sunlight against NHL, and they agree with geographic patterns of NHL incidence observed in the US.

Occupational exposure to ultraviolet radiation and risk of non-Hodgkin lymphoma

Individuals diagnosed with skin cancer have elevated risk of non-Hodgkin lymphoma, and those with non-Hodgkin lymphoma have excess rates of various types of skin cancers. Sunshine and other sources of ultraviolet radiation are major risk factors for skin cancer, and hence a potential common link between skin cancer and non-Hodgkin lymphoma. We analyzed the relationship between occupational exposure to ultraviolet radiation and the risk for non-Hodgkin lymphoma using data from a case-control study conducted in Northern Italy between 1985 and 1997. Cases were 446 patients with histologically confirmed incident non-Hodgkin lymphoma, and controls were 1295 patients admitted to hospital for acute non-neoplastic, non-immunological conditions. The multivariate odds ratios were computed after allowance for age, sex, area of residence, education and smoking. The odds ratio for patients reporting ever ultraviolet exposure at work was 1.01 (95% confidence interval 0.72-1.43) and 1.03 (95% confidence interval 0.72-1.49) for exposure longer than 10 years. The odds ratio was 1.09 for manual workers and 0.79 for farmers exposed to ultraviolet radiation, compared with those with other occupations not exposed to ultraviolet radiation. Our study found no association between occupational exposure to ultraviolet radiation and the risk of non-Hodgkin lymphoma.

Occupational trichloroethylene exposure and non-Hodgkin's lymphoma: a meta-analysis and review

METHODS

Meta-analysis and review of 14 occupational cohort and four case-control studies of workers exposed to trichloroethylene (TCE) to investigate the relation between TCE exposure and the risk of non-Hodgkin's lymphoma (NHL). Studies were selected and categorised based on a priori criteria, and results from random effects meta-analyses are presented.

RESULTS

The summary relative risk estimates (SRRE) for the group of cohort studies that had more detailed information on TCE exposure was 1.29 (95% CI 1.00 to 1.66) for the total cohort and 1.59 (95% CI 1.21 to 2.08) for the seven studies that identified a specific TCE exposed sub-cohort. SRREs for three studies with cumulative exposure information were 1.8 (95% CI 0.62 to 5.26) for the lowest exposure category and 1.41 (95% CI 0.61 to 3.23) for the highest category. Comparison of SRREs by levels of TCE exposure did not indicate exposure-response trends. The remaining cohort studies that identified TCE exposure but lacked detailed exposure information had an SRRE of 0.843 (95% CI 0.72 to 0.98). Case-control studies had an SRRE of 1.39 (95% CI 0.62 to 3.10). Statistically significant findings for the Group 1 studies were driven by the results from the subgroup of multiple industry cohort studies (conducted in Europe) (SRRE = 1.86; 95% CI 1.27 to 2.71). The SRRE for single industry cohort studies was not significantly elevated (SRRE = 1.25; 95% CI 0.87 to 1.79).

CONCLUSIONS

Interpretation of overall findings is hampered by variability in results across the Group 1 studies, limited exposure assessments, lack of evidence of exposure response trends, lack of supportive information from toxicological and mechanistic data, and absence of consistent findings in epidemiologic studies of exposure and NHL. Although a modest positive association was found in the TCE sub-cohort analysis, a finding attributable to studies that included workers from multiple industries, there is insufficient evidence to suggest a causal link between TCE exposure and NHL.

Does sunlight have a beneficial influence on certain cancers?

Apperly [1941. The relation of solar radiation to cancer mortality in North America. Cancer Research 1, 191-195] first proposed that increased mortality from cancer in the north than in the south of the USA might be due to the south to north decrease in ambient solar radiation. This inverse association between ambient solar radiation and cancer mortality has been subsequently reported for cancers of the colon, breast, ovary and prostate. While the evidence that sunlight might be related to lower incidence or more favourable outcomes from cancer came initially from ecological studies, case-control and cohort studies have now shown a similar association of sun exposure with risks of colon, breast and prostate cancers in individuals, and other studies in individuals have found that serum and dietary vitamin D levels are associated with reduced risks of colorectal cancer and, less certainly, prostate cancer. Studies in individuals have recently also suggested an effect of sun exposure to reduce risk of non-Hodgkin lymphoma and to increase survival after a diagnosis of melanoma. Data on variation in survival from cancer by season of diagnosis suggest that sun exposure may also improve outcome from cancers of the breast, colon and prostate and Hodgkin lymphoma.

Does sunlight prevent cancer? A systematic review

Accumulating evidence for beneficial effects of sunlight on several types of cancer with a high mortality rate makes it necessary to reconsider the health recommendations on sun exposure, which are now mainly based on the increased risks for skin cancer. We reviewed all published studies concerning sun exposure and cancer, excluding skin cancer. All selected studies on prostate (3 ecologic, 3 case-control and 2 cohort), breast (4 ecologic, 1 case-control and 2 cohort) and ovary cancer (2 ecologic and 1 case-control) showed a significantly inverse correlation between sunlight and mortality or incidence. Two ecologic, 1 case-control and 2 prospective studies showed an inverse relation between sunlight and colon cancer mortality; 1 case-control study found no such association. Ecologic studies on non-Hodgkin lymphoma (NHL) mortality and sunlight gave conflicting results: early studies showing mostly positive and later studies showing mostly negative correlations. Three case-control studies and 1 cohort study found a significant inverse association between the incidence of NHL and sunlight. The question of how to apply these findings to (public) health recommendations is discussed.

Exposure to non-arsenic pesticides is associated with lymphoma among farmers in Spain

OBJECTIVES

To estimate the risk of lymphoma among farmers in Spain.

METHODS

This is a multicentre case control study conducted in Spain. Cases were subjects diagnosed with lymphoma according to the World Health Organization (WHO) classification in four hospitals between 1998-2002. Hospital controls were frequency matched to the cases by sex, age, and centre. All subjects were interviewed about jobs ever held in lifetime for at least one year and the exposures in those jobs were recorded. The risk of lymphomas among subjects ever having had a job as a farmer was compared with all other occupations. Farmers were analysed according to the type of farming job performed: crop farming, animal farming, and general farming. Occupational exposure was summarised into 15 main categories: organic dust, radiation, contact with animals, PAH, non-arsenic pesticides (carbamates, organophosphates, chlorinated hydrocarbons, triazines and triazoles, phenoxy herbicides, chlorophenols, dibenzodioxin, and dibenzofuran), arsenic pesticides, contact with meat, contact with children, solvents, asbestos, soldering fumes, organic colourants, polychlorinated biphenyls, ethylene oxide, and hair dyes.

RESULTS

Although farmers were not at an increased risk of lymphoma as compared with all other occupations, farmers exposed to non-arsenic pesticides were found to be at increased risk of lymphoma (OR = 1.8, 95% CI 1.1 to 2). This increased risk was observed among farmers working exclusively either as crop farmers or as animal farmers (OR = 2.8, 95% CI 1.3 to 5.8). Risk was highest for exposure to non-arsenic pesticides for over nine years (OR = 2.4, 95% CI 1.2 to 2.8).

CONCLUSIONS

Long term exposure to non-arsenic pesticides may induce lymphomagenesis among farmers.

Effect of light irradiation and sex hormones on jurkat T cells: 17beta-estradiol but not testosterone enhances UVA-induced cytotoxicity in Jurkat lymphocytes

In Eastern cultures, such as India, it is traditionally recommended that women but not men cover their heads while working in the scorching sun. The purpose of this pilot study was to determine whether there was any scientific basis for this cultural tradition. We examined the differential cytotoxic effects of ultraviolet A light (UVA) on an established T cell line treated with female and male sex hormones. CD4⁺ Jurkat T cells were plated in 96 well plates at 2 × 10⁶ cells/ml and treated with 17β-estradiol (EST) or testosterone (TE). These cells were irradiated by UVA light with an irradiance of 170 J/cm² for 15min at a distance of 6 cm from the surface of the 96-well plate. Controls included cells not treated with hormones or UVA. The effects of EST and TE were investigated between 1 and 20 ng/mL. Cytotoxicity by fluorescein-diacetate staining and COMET assay generating single strand DNA cleavage, tail length and tail moment measurements were examined. The effect of estrogen (5ng/mL) on apoptosis and its mediators was further studied using DNA laddering and western blotting for bcl-2 and p53. We found that EST alone, without UVA, enhanced Jurkat T cell survival. However, EST exhibited a dose-related cytotoxicity in the presence of UVA; up to 28% at 20 ng/ml. TE did not alter UVA-induced cytotoxicity. Since TE did not alter cell viability in the presence of UVA further damaging studies were not performed. COMET assay demonstrated the harmful effects of EST in the presence of UVA while EST without UVA had no significant effect on the nuclear damage. Apoptosis was not present as indicated by the absence of DNA laddering on agarose gel electrophoresis at 5ng/ml EST or TE ± UVA. Western blot showed that estrogen down regulated bcl-2 independently of UVA radiation while p53 was down regulated in the presence of UVA treatment. EST and TE have differential effects on UVA-induced cytotoxicity in Jurkat T-lymphocyte which suggested that women may be more susceptible to the harmful effects of solar irradiation than men.

Solar cycles and their relationship to human disease and adaptability

In this paper, we show that 11-year solar cycle peaks predispose humans to disease, but also endow creativity and adaptability. We give several examples of diseases that are modulated by light and present evidence for an effect of intensity and variation in sunlight, primarily ultraviolet radiation (UVR), on the human genome. The birth dates of nearly 237,000 unique clients in the Maine Medicaid database collected from 1995 to 2004, inclusive, were related to solar cycle irradiance for the past seventy-one years, encompassing seven solar cycles. The sample was divided into four general categories of disease: mental/behavioral illnesses; metabolic diseases; autoimmune diseases; neoplasms. The birth months for those clients born in any given year were arranged in the form of a winter/summer ratio in order to more clearly appreciate the seasonality inherent in each disease category. Solar cycles were separated into chaotic (approximately three times as irradiant) or non-chaotic according to the Gutenberg-Richter power law and the uncertainty inherent in predicting solar storms. The results show that radiation peaks in solar cycles and particularly in chaotic solar cycles (CSCs) are associated with a higher incidence of mental disorders, suggesting the sensitivity of ectodermal embryonic tissues to UVR. Autoimmune diseases have intermediate sensitivity, while the neoplasms in the study, primarily of endoderm, appear suppressed by peak UVR intensity. The ratio of the number of clients born in CSC cycles to non-CSC cycles was highest for the more genetic mental diseases, like schizophrenia and bipolar disorder, but as that ratio decreased, the clients with diseases like multiple sclerosis and rheumatoid arthritis showed more environmental features manifested as a greater winter/summer birth month ratio that was significantly different than that of the average client in the whole data set. The paper presents evidence that latitude, e.g., variation in light, is an added stress to the immune system (especially at 53-54 degrees N. latitude) that is involved in nearly all human disease. We hypothesize that introns, the presumptive engenderers of gene control, modulate the effects of UVR, particularly for the neoplasms studied. We conclude that intermittent and largely unpredictable peak solar cycle radiation has been the fundamental engine of evolution, forcing organisms to adapt to mutagenic UVR and producing enough damage to instigate genetic variation. Probably a chance genetic mutation over 80,000 years ago produced a human brain capable of abstract thought and consciousness. The slight genetic instability that favored an adaptable, creative brain also produced other somatic variations that present phenotypically as disease, but largely expressed after natural selection (reproduction) and associated with the inexorable entropy of aging.

Skin cancer and non-Hodgkin's lymphoma: examining the link

BACKGROUND

The incidence rates of melanoma and non-Hodgkin's lymphoma (NHL) have increased substantially worldwide over the past several decades. It has been hypothesized that ultraviolet light exposure through sunlight may be a common environmental risk factor shared by both skin cancer and NHL.

OBJECTIVE

The purpose of this study was to better understand the association between skin cancer and NHL and to evaluate its implication in clinical practice.

METHODS

We reviewed the current literature on the link between the two malignancies and on the role of ultraviolet light in the development of NHL. Publications were selected using a PUBMED search with the terms "non-Hodgkin's lymphoma" and "skin cancer." Epidemiologic studies in English and published after 1995 were the focus.

CONCLUSIONS

Large population-based studies support an increased risk of subsequent NHL among patients with skin cancers (both melanoma and nonmelanoma skin cancers) and a risk of skin cancer development in patients with NHL, although support for a direct relationship between ultraviolet light and the incidence of NHL is weak and inconsistent. Given their increased risk of developing skin cancers, patients with a history of NHL may benefit from a full-body examination during their visits.

Ultraviolet Radiation Exposure and Risk of Malignant Lymphomas

BACKGROUND

The incidence of malignant lymphomas has been increasing rapidly, but the causes of these malignancies remain poorly understood. One hypothesis holds that exposure to ultraviolet (UV) radiation increases lymphoma risk. We tested this hypothesis in a population-based case-control study in Denmark and Sweden.

METHODS

A total of 3740 patients diagnosed between October 1, 1999, and August 30, 2002, with incident malignant lymphomas, including non-Hodgkin lymphoma, chronic lymphocytic leukemia, and Hodgkin lymphoma, and 3187 population controls provided detailed information on history of UV exposure and skin cancer and information on other possible risk factors for lymphomas. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by logistic regression. Statistical tests were two-sided.

RESULTS

Multivariable-adjusted analyses revealed consistent, statistically significant negative associations between various measures of UV light exposure and risk of non-Hodgkin lymphoma. A high frequency of sun bathing and sunburns at age 20 years and 5-10 years before the interview and sun vacations abroad were associated with 30%-40% reduced risks of non-Hodgkin lymphoma (e.g., for sunbathing four times a week or more at age 20 versus never sunbathing, OR = 0.7, 95% CI = 0.6 to 0.9; for two or more sunburns a year at age 20 versus no sunburns, OR = 0.6, 95% CI = 0.5 to 0.8). These inverse associations increased in strength with increasing levels of exposure (all P(trend)< or =.01). Similar, albeit weaker, associations were observed for Hodgkin lymphoma. There were no clear differences among non-Hodgkin lymphoma subtypes, although associations were stronger for B-cell than for T-cell lymphomas. A history of skin cancer was associated with a doubling in risks of both non-Hodgkin and Hodgkin lymphoma.

CONCLUSIONS

A history of high UV exposure was associated with reduced risk of non-Hodgkin lymphoma. The positive association between skin cancer and malignant lymphomas is, therefore, unlikely to be mediated by UV exposure.

Epidemiology of non-Hodgkin's lymphoma (NHL): trends, geographic distribution, and etiology

While for most cancers incidence and mortality are decreasing, those of non-Hodgkin's lymphoma (NHL) are steadily increasing. Research to define reasons for this increase is extensive, but has not yet resolved them. We have conducted a literature analysis on trends regarding changes in the incidence, geographic distribution, and etiologic factors of NHL. From our own and previous analyses, an increasing NHL incidence at a rate of 3-4% per year was observed for the 1970s and 1980s. This stabilized in the 1990s, nevertheless still with an annual rise of 1-2%, resulting in almost a doubling of the NHL incidence. This rise has been noted worldwide, particularly in elderly persons >55 years. Concerning gender subgroups, a male predominance throughout all age groups is apparent. Although the NHL incidence has historically been higher in whites than blacks, disproportional increases have recently been observed in the latter group. Increases in high-grade NHL and extranodal disease are predominant. Differences in geographic distribution are striking for follicular lymphoma, which is more common in Western countries than elsewhere. Asians have higher rates of aggressive NHL, T-cell lymphomas, and extranodal disease. In the Middle East, high rates of intestinal extranodal disease are observed, whereas in Africa, endemic Burkitt's lymphoma accounts for a substantial proportion. Risks for developing NHL include immunosuppression and a causal link between infectious agents, and lymphomagenesis has also been determined, particularly for human T-cell leukemia/lymphoma virus type 1 (HTLV-1), Epstein-Barr virus (EBV), and Helicobacter pylori infections. Exposure to environmental agents and occupational risks have been studied; however, their significance is as yet uncertain.

Sun exposure may protect against non-Hodgkin lymphoma: A case-control study

Ultraviolet radiation is a hypothesised risk factor for non-Hodgkin lymphoma (NHL) but no epidemiological study has examined this association using direct measures of sun exposure in individuals. Adults aged 20-74 years living in NSW and ACT, Australia, were the study population. Cases (704 of 829 invited to take part, 85%) were diagnosed January 2000 to August 2001. Controls (694 of 1,136 invited to take part, 61%) were randomly selected from state electoral rolls and frequency-matched to cases by age, sex and state of residence. A self-administered questionnaire and telephone interview measured outdoor hours on working and nonworking days and vacations at 10, 20, 30, 40, 50 and 60 years of age. Logistic regression models of NHL and sun exposure contained the 3 matching variables, ethnicity and sun sensitivity measures as covariates. Contrary to expectations, risk of NHL fell with increasing reported sun exposure hours. Relative to 1.0 for the lowest quarter of total sun exposure hours, the odds ratios (ORs) for successively higher quarters were 0.72 (95% CI 0.53-0.98), 0.66 (0.48-0.91) and 0.65 (0.46-0.91) (p(trend)=0.01). The association of sun exposure on nonworking days with NHL was stronger; OR for highest quarter 0.47 (0.34-0.66) (p(trend)=0.0001). Risk also fell with sun exposure on vacations; OR for highest quarter 0.60 (0.43-0.85) (p(trend)=0.003). These associations appeared strongest in women and in childhood. There was little evident trend in risk with exposure on working day. Our results provide strong statistical evidence for an inverse association between sun exposure and NHL. Increasing evidence that vitamin D may protect against cancer makes UV-mediated synthesis of vitamin D a plausible mechanism whereby sun exposure might protect against NHL.