On recent meta-analyses of exposure to glyphosate and risk of non-Hodgkin's lymphoma in humans

PURPOSE

A recent meta-analysis of five case-control studies and one cohort study reported that exposure to glyphosate was associated with increased risk of non-Hodgkin's lymphoma (NHL). The meta-analysis was based on estimates of risk from the included studies at the highest reported exposure level obtained from analyses with the longest lag period. The extent to which the summary estimate depends upon the exposure definitions and assumed latency period is uncertain.

METHODS

We carried out sensitivity analyses to determine how the definition of exposure and the choice of latency period affect the summary estimate from meta-analyses of the 6 studies included in the recent meta-analysis. We also conducted a meta-analysis of ever-exposure to glyphosate incorporating the most updated results from the case-control studies.

RESULTS

The summary estimates of risk varied considerably depending on both the assumptions about exposure level and latency. Using the highest reported exposure levels, evidence of an association between glyphosate and NHL was strongest when estimates from analyses in the cohort study with a 20-year lag [RR = 1.41 (95% CI 1.13-1.76)] and a 15-year lag [RR = 1.25 (95% CI 1.01-1.25)] were included. In our meta-analysis of ever-exposure with no lag period, the summary relative risk with updated estimates was 1.05 (95% CI 0.87-1.28).

CONCLUSION

The results of meta-analyses of glyphosate exposure and NHL risk depend on assumptions made about both exposure level and latency period. Our results for ever-exposure are consistent with those of two recent meta-analyses conducted using somewhat different study inclusion criteria.

On the International Agency for Research on Cancer classification of glyphosate as a probable human carcinogen

The recent classification by International Agency for Research on Cancer (IARC) of the herbicide glyphosate as a probable human carcinogen has generated considerable discussion. The classification is at variance with evaluations of the carcinogenic potential of glyphosate by several national and international regulatory bodies. The basis for the IARC classification is examined under the assumptions that the IARC criteria are reasonable and that the body of scientific studies determined by IARC staff to be relevant to the evaluation of glyphosate by the Monograph Working Group is sufficiently complete. It is shown that the classification of glyphosate as a probable human carcinogen was the result of a flawed and incomplete summary of the experimental evidence evaluated by the Working Group. Rational and effective cancer prevention activities depend on scientifically sound and unbiased assessments of the carcinogenic potential of suspected agents. Implications of the erroneous classification of glyphosate with respect to the IARC Monograph Working Group deliberative process are discussed.

Menthol and Nonmenthol Cigarette Smoking: All-Cause Deaths, Cardiovascular Disease Deaths, and Other Causes of Death Among Blacks and Whites

BACKGROUND

In contrast to whites, black smokers prefer menthol cigarettes over nonmenthol cigarettes by a large margin and tend to have higher mortality from several smoking-related diseases than whites, raising the possibility that menthol cigarettes contribute to racial disparities in risk. Evidence for differential associations between menthol and nonmenthol cigarettes indicates lower cancer risk for menthol smokers, but for cardiovascular disease (CVD) mortality, evidence has been inconsistent.

METHODS AND RESULTS

Cox proportional hazards models were used to compute hazard ratios and accompanying 95% confidence intervals for all-cause and CVD mortality for menthol compared with nonmenthol cigarette smokers among 65 600 participants in the Southern Community Cohort Study, an ongoing community-based cohort with the largest number of menthol smokers being traced. Among the 27 619 current cigarette smokers, 4224 died during follow-up, with 1130 deaths attributed to CVD. Both all-cause (hazard ratio=0.93; 95% confidence interval=0.86-1.01; P=0.10) and CVD (hazard ratio=0.88; 95% confidence interval=0.76-1.03; P=0.10) mortality risks were similar in menthol compared with nonmenthol cigarette smokers.

CONCLUSIONS

Smoking regardless of cigarette type is hazardous to health, but these results do not indicate that menthol cigarettes are associated with greater CVD risks than nonmenthol cigarettes.

Suicides, homicides, accidents, and other external causes of death among blacks and whites in the Southern Community Cohort Study

Prior studies of risk factors associated with external causes of death have been limited in the number of covariates investigated and external causes examined. Herein, associations between numerous demographic, lifestyle, and health-related factors and the major causes of external mortality, such as suicide, homicide, and accident, were assessed prospectively among 73,422 black and white participants in the Southern Community Cohort Study (SCCS). Hazard ratios (HR) and 95% confidence intervals (CI) were calculated in multivariate regression analyses using the Cox proportional hazards model. Men compared with women (HR = 2.32; 95% CI: 1.87-2.89), current smokers (HR = 1.74; 95% CI: 1.40-2.17), and unemployed/never employed participants at the time of enrollment (HR = 1.67; 95% CI 1.38-2.02) had increased risk of dying from all external causes, with similarly elevated HRs for suicide, homicide, and accidental death among both blacks and whites. Blacks compared with whites had lower risk of accidental death (HR = 0.46; 95% CI: 0.38-0.57) and suicide (HR = 0.55; 95% CI: 0.31-0.99). Blacks and whites in the SCCS had comparable risks of homicide death (HR = 1.05; 95% CI: 0.63-1.76); however, whites in the SCCS had unusually high homicide rates compared with all whites who were resident in the 12 SCCS states, while black SCCS participants had homicide rates similar to those of all blacks residing in the SCCS states. Depression was the strongest risk factor for suicide, while being married was protective against death from homicide in both races. Being overweight/obese at enrollment was associated with reduced risks in all external causes of death, and the number of comorbid conditions was a risk factor for iatrogenic deaths. Most risk factors identified in earlier studies of external causes of death were confirmed in the SCCS cohort, in spite of the low SES of SCCS participants. Results from other epidemiologic cohorts are needed to confirm the novel findings identified in this study.

A prospective study of statin use and mortality among 67,385 blacks and whites in the Southeastern United States

Purpose

The primary objective of this study is to examine the race-specific associations between statin use and overall mortality, as well as cardiovascular and cancer mortality, among blacks and whites in the Southeastern United States (US). Little is known about these associations in blacks.

Patients and methods

The Southern Community Cohort Study is an ongoing, prospective cohort study, which enrolled from 2002 through 2009 nearly 86,000 participants aged 40–79 years. We used Cox regression models to estimate race-specific hazard ratios (HRs) and 95% confidence intervals (CI) for overall and cause-specific mortality associated with statin use based on self-reported hypercholesterolemia and treatment at cohort entry. Mean age at cohort entry was 51.4 years in blacks (n=48,825) and 53.5 years in whites (n=18,560). Sixty-one percent of participants were women. Whites were more likely to have self-reported hypercholesterolemia (40% versus 27%, P<0.001), and to report being treated with either statins (52% versus 47%, P<0.001) or combination lipid therapy (9% versus 4%, P<0.001) compared with blacks, regardless of sex. During follow-up (median: 5.6 years) 5,199 participants died. Compared with untreated hypercholesterolemic individuals, statin use was associated with reduced all-cause mortality (adjusted HR [aHR] 0.86; 95% CI 0.77–0.95) and cardiovascular disease mortality overall (aHR 0.75; 95% CI 0.64–0.89) and among whites (aHR 0.67; 95% CI 0.50–0.90), blacks (aHR, 0.80; 95% CI 0.65–0.98), men (aHR 0.70; 95% CI 0.55–0.90), and women (aHR 0.79; 95% CI 0.63–0.99) (P>0.05 for race and sex interaction). Statin use was not associated with cancer mortality overall or in subgroup analyses.

Conclusion

Regardless of race or sex, self-reported statin use was linked to reduced all-cause and cardiovascular disease mortality. However, factors contributing to the modestly lower statin use and markedly lower prevalence of self-reported hypercholesterolemia among blacks remain to be determined.

False positives in cancer epidemiology

BACKGROUND

A recent attempt to estimate the false-positive rate for cancer epidemiology studies is based on agents in International Agency for Research on Cancer (IARC) category 3 (agent not classifiable as to its carcinogenicity to humans) in the IARC Monographs Program.

METHODS

The estimation method is critiqued regarding biases caused by its reliance on the IARC classification criteria for assessing carcinogenic potential.

RESULTS

The privileged position given to epidemiologic studies by the IARC criteria ensures that the percentage of positive epidemiologic studies for an agent will depend strongly on the IARC category to which the agent is assigned. Because IARC category 3 is composed of agents with the lowest-assessed carcinogenic potential to which the estimation approach in question could be applied, a spuriously low estimated false-positive rate was necessarily the outcome of this approach.

CONCLUSIONS

Tendentious estimation approaches like that employed will by necessity produce spuriously low and misleading false positive rates.

IMPACT

The recently reported estimates of the false-positive rate in cancer epidemiology are seriously biased and contribute nothing substantive to the literature on the very real problems related to false-positive findings in epidemiology.

Incidence and predictors of end stage renal disease among low-income blacks and whites

We evaluated whether black race is associated with higher incidence of End Stage Renal Disease (ESRD) among a cohort of blacks and whites of similar, generally low socioeconomic status, and whether risk factor patterns differ among blacks and whites and explain the poorly understood racial disparity in ESRD. Incident diagnoses of ESRD among 79,943 black and white participants in the Southern Community Cohort Study (SCCS) were ascertained by linkage with the United States Renal Data System (USRDS) from 2002 through 2009. Person-years of follow up were calculated from date of entry into the SCCS until date of ESRD diagnosis, date of death, or September 1, 2009, whichever occurred first. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CI) for incident ESRD among black and white participants in relation to baseline characteristics. After 329,003 person-years of follow-up, 687 incident cases of ESRD were identified in the cohort. The age-adjusted ESRD incidence rate was 273 (per 100,000) among blacks, 3.5-fold higher than the rate of 78 among whites. Risk factors for ESRD included male sex (HR = 1.6; 95% CI 1.4–1.9), low income (HR = 1.5; 95% CI 1.2–1.8 for income below vs. above $15,000), smoking (HR = 1.2; 95% CI 1.02–1.4) and histories of diabetes (HRs increasing to 9.4 (95% CI 7.4–11.9) among those with ≥20 years diabetes duration) and hypertension (HR = 2.9; 95% CI 2.3–3.7). Patterns and magnitudes of association were virtually identical among blacks and whites. After adjustment for these risk factors, blacks continued to have a higher risk for ESRD (HR = 2.4; 95% CI = 1.9–3.0) relative to whites. The black-white disparity in risk of ESRD was attenuated but not eliminated after control for known risk factors in a closely socioeconomically matched cohort. Further research characterizing biomedical factors, including CKD progression, in ESRD occurrence in these two racial groups is needed.

Cancer incidence among workers at a satellite manufacturing facility

OBJECTIVE

To evaluate cancer incidence overall and renal cancer in particular among workers at the Valley Forge satellite manufacturing complex in Pennsylvania. A previous mortality study observed a slightly elevated risk estimate for brain cancer.

METHODS

A cohort of 27,586 workers, employed between 1962 and 2008 and alive in 1990 when cancer follow-up began, was investigated. Standardized incidence ratios (SIRs) were calculated.

RESULTS

A total of 4303 incident cancers were diagnosed. The SIRs were significantly reduced for all cancers (0.88; 95% confidence interval [CI], 0.85 to 0.90) and several site-specific cancers. The renal cancer SIR was 1.00 (95% CI, 0.84 to 1.19) and the brain cancer SIR was 1.17 (95% CI, 0.90 to 1.49).

CONCLUSIONS

This cancer incidence study of satellite manufacturing workers found no convincing evidence of increased cancer risk overall, or for renal or brain cancer in particular.

Renal cell cancer among African Americans: an epidemiologic review

Incidence rates for renal cell cancer, which accounts for 85% of kidney cancers, have been rising more rapidly among blacks than whites, almost entirely accounted for by an excess of localized disease. This excess dates back to the 1970s, despite less access among blacks to imaging procedures in the past. In contrast, mortality rates for this cancer have been virtually identical among blacks and whites since the early 1990s, despite the fact that nephrectomy rates, regardless of stage, are lower among blacks than among whites. These observations suggest that renal cell cancer may be a less aggressive tumor in blacks. We have reviewed the epidemiology of renal cell cancer, with emphasis on factors which may potentially play a role in the observed differences in incidence and mortality patterns of renal cell cancer among blacks and whites. To date, the factors most consistently, albeit modestly, associated with increased renal cell cancer risk in epidemiologic studies among whites--obesity, hypertension, cigarette smoking--likely account for less than half of these cancers, and there is virtually no epidemiologic evidence in the literature pertaining to their association with renal cell cancer among blacks. There is a long overdue need for detailed etiologic cohort and case-control studies of renal cell cancer among blacks, as they now represent the population at highest risk in the United States. In particular, investigation of the influence on renal cell cancer development of hypertension and chronic kidney disease, both of which occur substantially more frequently among blacks, is warranted, as well as investigations into the biology and natural history of this cancer among blacks.

Racial differences in serum cotinine levels of smokers

The purpose of this study was to estimate black/white differences in cotinine levels for current smokers of both sexes, and to explore the potential contribution of mentholated cigarettes to these differences. Sera from 255 current smokers sampled from Southern Community Cohort Study participants (65 black men, 65 black women, 63 white men, 62 white women) were analyzed for cotinine, and linear regression was used to model the effect of race on cotinine level, adjusting for the number of cigarettes smoked within the last 24 hours, use of menthol vs. non-menthol cigarettes, exposure to environmental tobacco smoke, and age. Black smokers smoked fewer cigarettes than white smokers, yet had crude mean cotinine levels nearly as high or higher than white smokers. After multivariate adjustment, cotinine levels were an average of 50 ng/ml higher among black than white women (p=0.008) and non-significantly 12 ng/ml higher among black than white men (p=0.52). We observed no increase in cotinine levels associated with menthol cigarette use. We conclude that differences in cotinine levels among smokers suggest racial variation in exposure to and/or metabolism of tobacco smoke constituents, but our findings do not support a role for menthol preference in this disparity.

Epidemiologic characteristics and risk factors for renal cell cancer

Incidence rates of renal cell cancer, which accounts for 85% of kidney cancers, have been rising in the United States and in most European countries for several decades. Family history is associated with a two- to four-fold increase in risk, but the major forms of inherited predisposition together account for less than 4% of renal cell cancers. Cigarette smoking, obesity, and hypertension are the most consistently established risk factors. Analgesics have not been convincingly linked with renal cell cancer risk. A reduced risk of renal cell cancer among statin users has been hypothesized but has not been adequately studied. A possible protective effect of fruit and vegetable consumption is the only moderately consistently reported dietary finding, and, with the exception of a positive association with parity, evidence for a role of hormonal or reproductive factors in the etiology of renal cell cancer in humans is limited. A recent hypothesis that moderate levels of alcohol consumption may be protective for renal cell cancer is not strongly supported by epidemiologic results, which are inconsistent with respect to the categories of alcohol consumption and the amount of alcohol intake reportedly associated with decreased risk. For occupational factors, the weight of the evidence does not provide consistent support for the hypotheses that renal cell cancer may be caused by asbestos, gasoline, or trichloroethylene exposure. The established determinants of renal cell cancer, cigarette smoking, obesity, and hypertension, account for less than half of these cancers. Novel epidemiologic approaches, including evaluation of gene–environment interactions and epigenetic mechanisms of inherited and acquired increased risk, are needed to explain the increasing incidence of renal cell cancer.

County mortality and cancer incidence in relation to living near two former nuclear materials processing facilities in Pennsylvania--an update

A previous county mortality study of populations living near two nuclear materials processing and fabrication facilities in Westmoreland and Armstrong counties in Pennsylvania (1950-1995) was extended through 2004. Noncancer mortality (1996-2004) and cancer incidence (1990-2004) were also evaluated. Among the Westmoreland and Armstrong populations, 10,547 cancer deaths occurred during the period 1996 through 2004 and the relative risk (RR) based on comparisons with six demographically similar counties in western Pennsylvania was 0.97, that is, almost exactly as expected, and no different from our previously published analyses covering the years 1950-1995. The results based on cancer incidence data were very similar to those based on cancer mortality data. Over the years 1990 though 2004, 39,350 incident cancers were reported among residents of Armstrong and Westmoreland counties and the RR based on the six demographically similar counties was 0.99, that is, almost exactly as expected. The number of deaths from nonmalignant conditions was 36,565 and very close to the number expected (RR 1.01). Overall, no increases in cancer or nonmalignant diseases could be attributed to living in counties with nuclear materials processing and fabrication facilities.

Risk of cholecystitis in patients with cancer: a population-based cohort study in Denmark

BACKGROUND

To the authors' knowledge, little information is available regarding the incidence of cholecystitis among patients with cancer.

METHODS

The authors conducted a population-based historical cohort study of 51,228 patients with incident cancer, identified in medical databases of western Denmark between 1995 and 2003. A general population comparison cohort of 512,280 persons was assembled using the Danish Civil Registration System. The occurrence of cholecystitis in the 2 groups was determined by linkage to the regional Hospital Discharge Registry.

RESULTS

In all, 230 incident diagnoses of cholecystitis were identified in the cancer cohort during 130,185 person-years (median follow-up time: 1.6 years), corresponding to an incidence rate of 1.8 of 1000 person-years. After adjustment for confounders, the relative risk (RR) for cholecystitis among cancer patients compared with the general population cohort was 1.38 (95% confidence interval [95% CI], 1.20-1.58). Overall, the RR for cholecystitis was doubled during the first 6 months after cancer diagnosis (RR = 1.95; 95% CI, 1.50-2.54), after which the RR declined but remained greater than 1 throughout the rest of the follow-up period (RR = 1.23; 95% CI, 1.05-1.45). Cancer patients between the ages of 51 and 70 years had the highest risk increase for cholecystitis compared with other age groups. During the first 6 months after a cancer diagnosis, pancreatic cancers (12 cholecystitis events; RR = 9.44 [95% CI, 5.18-17.18]) and colorectal cancers (10 cholecystitis events; RR = 4.98 [95% CI, 2.65-9.34]) were found to be associated with the greatest cholecystitis risk increase compared with other tumor types. After 6 months, most cancers were associated with a relatively small increased risk, although there was an RR of 4.72 (95% CI, 1.99-11.21) based on 5 cholecystitis events among thyroid cancer patients.

CONCLUSIONS

The results of the current study indicate that cholecystitis occurs more frequently among cancer patients than in the general population, particularly within the first 6 months after a cancer diagnosis. Clinicians who treat cancer patients should remain vigilant about this type of infection.

Cancer among Scandinavian women with cosmetic breast implants: a pooled long-term follow-up study

No increased risks of specific types of cancer following breast implantation have been consistently reported, but data on risk beyond 15 years are limited. We have pooled the results of 2 nationwide cohort studies of 3,486 Swedish and 2,736 Danish women who underwent cosmetic breast implantation between 1965 and 1993. Cancer incidence through 2002 was ascertained through nationwide cancer registries. Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) were calculated to compare cancer incidence among women with implants with women in the general population. Mean duration of follow up was 16.6 years (range 0.1-37.8 years). Over 50% of women were followed for 15 years or more after breast implantation and 13.3% for at least 25 years. There was a reduced incidence of breast cancer (SIR=0.73; 95% CI 0.58-0.90), whereas lung cancer was above expectation (SIR=1.64; 95% CI 1.10-2.36). The increased risk of lung cancer is expected due to the high prevalence of smoking among the women with implants in our study. With respect to other site-specific cancers, no significantly increased or decreased SIR was observed. This study, which includes women followed for almost 4 decades, represents the longest follow up of women with cosmetic breast implants to date. The results provide no evidence of an association between breast implants and any type of cancer.

False-positive results in cancer epidemiology: a plea for epistemological modesty

False-positive results are inherent in the scientific process of testing hypotheses concerning the determinants of cancer and other human illnesses. Although much of what is known about the etiology of human cancers has arisen from well-conducted epidemiological studies, epidemiology has been increasingly criticized for producing findings that are often sensationalized in the media and fail to be upheld in subsequent studies. Herein we describe examples from cancer epidemiology of likely false-positive findings and discuss conditions under which such results may occur. We suggest general guidelines or principles, including the endorsement of editorial policies requiring the prominent listing of study caveats, which may help reduce the reporting of misleading results. Increased epistemological humility regarding findings in epidemiology would go a long way to diminishing the detrimental effects of false-positive results on the allocation of limited research resources, on the advancement of knowledge of the causes and prevention of cancer, and on the scientific reputation of epidemiology and would help to prevent oversimplified interpretations of results by the media and the public.

Fetal growth indicators and perfluorinated chemicals: a study in the Danish National Birth Cohort

Perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) are widespread persistent organic pollutants that have been associated with reduced birth weight at doses expected in many pregnant populations. The authors randomly selected 1,400 pregnant women and their newborns from the Danish National Birth Cohort (1996-2002) to investigate whether these compounds reduce organ growth. PFOS and PFOA were measured in maternal blood samples taken early in pregnancy. Placental weight, birth length, and head and abdominal circumferences were measured shortly after birth by trained midwives or nurses. Maternal PFOA levels in early pregnancy were associated with smaller abdominal circumference and birth length. For each ng/ml increase in PFOA, birth length decreased by 0.069 cm (95% confidence interval: 0.024, 0.113) and abdominal circumference decreased by 0.059 cm (95% confidence interval: 0.012, 0.106). An inverse association was also observed between PFOA and placental weight and head circumference, and a positive association was observed with newborn ponderal index, but none of these associations was statistically significant. Maternal PFOS levels were not associated with any of the five fetal growth indicators. These findings suggest that fetal exposure to PFOA but not PFOS during organ development may affect the growth of organs and the skeleton.

Endoscopic sphincterotomy and long-term risk of cholangiocarcinoma: a population-based follow-up study

Sphincterotomy of the ampulla of Vater--a common diagnostic and therapeutic procedure that is sometimes done during endoscopic retrograde cholangiography (ERC)--allows reflux of intestinal content into the biliary tree. The resulting inflammation may contribute to malignant transformation of the biliary epithelium and therefore increase the risk of cholangiocarcinoma. We used data from population-based Danish health-care registries to examine the incidence of cholangiocarcinoma after ERC for 10 690 ERC patients who underwent sphincterotomy between 1977 and 2003 and 10,690 ERC patients who did not undergo sphincterotomy. Patients with sphincterotomy were matched to patients without sphincterotomy by sex and age at, calendar year of, and indication for ERC. The cholangiocarcinoma incidence rate for sphincterotomy patients was 404 per 100,000 person-years during the first year after ERC and decreased progressively at later times after ERC (79, 42, and 27 per 100,000 person-years during years 2, 3-5, and > 5, respectively). The corresponding rates for patients without sphincterotomy were 458, 12, 10, and 19 per 100,000 person-years, respectively. The gradual decrease in cholangiocarcinoma rate over time after ERC for sphincterotomy patients indicates that some of these patients had a cholangiocarcinoma that was present at the time of ERC but not diagnosed until 2-5 years later. The similar rates at the latest times after ERC suggest the lack of a causal association between sphincterotomy and cholangiocarcinoma.

Comparison of in vivo translocation frequencies with in vitro G2 radiosensitivity in radiation workers occupationally exposed to external radiation

A group of retired workers from the British Nuclear Fuels plc facility at Sellafield who had been studied for in vivo translocation frequencies in blood lymphocytes were resampled and analysed for in vitro chromosomal radiosensitivity. Significant variation in response to a dose of 0.5 Gy given at the G(2) stage of the cell cycle was observed between individuals (P < 0.001). In a regression analysis that included age, cumulative occupational radiation dose and in vitro G(2) radiation-induced aberration frequencies as independent variables, only cumulative occupational radiation dose had a significant influence on chromosomal translocation frequency (P = 0.0036). G(2) in vitro radiosensitivity is assumed to be a marker for genetic polymorphic variation in DNA damage recognition and repair genes. Therefore, since in vivo translocation frequencies can be considered a surrogate for cancer risk, this lack of association with G(2) in vitro radiosensitivity suggests that such genetic variation has no impact on the response to low dose chronic exposure.

Incidence rates of hepatocellular carcinoma in the U.S. and Denmark: recent trends

Hepatocellular carcinoma (HCC) incidence rates vary by gender, age, time and place. Geographic differences in gender-, age- and time-specific HCC incidence rates may improve the understanding of HCC risk factors. We computed annual standardized HCC incidence rates for the United States (U.S.) 1978-2004 and for Denmark 1978-2003. Among U.S. white men aged 45-59 the HCC incidence rates were comparable to the Danish rates until 1995, but more than tripled over the following 8 years to become over 2.5-fold higher than the Danish rate by 2003, with an additional small increase in 2004. HCC rates in black U.S. men aged 45-59 also increased sharply after 1995. Among women aged 45-59 the U.S. HCC rates were elevated in recent years, but did not show the sharp increase after 1995 observed among men; the Danish rates showed a decreasing trend throughout 1978-2003. U.S. rates in the 60-74 years age groups showed a protracted and gradual increase with no evidence of a sharp increase after 1995. In the 60-74 years age group, rates for Danish men were comparable to those for U.S. white men, but rates for Danish women decreased. The U.S. prevalence rates of hepatitis C virus (HCV) infection are 2.1 and 1.1% for men and women, respectively, the Danish 0.2%. The disparity in HCV prevalence is the most likely explanation for the differences between Danish and U.S. trends in HCC incidence. Intravenous drug use and blood transfusions are the major sources of HCV, and we suggest that increased HCV infection prevalence among Vietnam era military veterans may contribute to the earlier and steeper HCC incidence increase for U.S. men than for U.S. women.

Perfluorinated chemicals and fetal growth: a study within the Danish National Birth Cohort

BACKGROUND

Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) are man-made, persistent organic pollutants widely spread throughout the environment and human populations. They have been found to interfere with fetal growth in some animal models, but whether a similar effect is seen in humans is uncertain.

OBJECTIVES

We investigated the association between plasma levels of PFOS and PFOA in pregnant women and their infants' birth weight and length of gestation.

METHODS

We randomly selected 1,400 women and their infants from the Danish National Birth Cohort among those who completed all four computer-assisted telephone interviews, provided the first blood samples between gestational weeks 4 and 14, and who gave birth to a single live-born child without congenital malformation. PFOS and PFOA were measured by high performance liquid chromatography-tandem mass spectrometer.

RESULTS

PFOS and PFOA levels in maternal plasma were on average 35.3 and 5.6 ng/mL, respectively. Only PFOA levels were inversely associated with birth weight (adjusted beta = -10.63 g; 95% confidence interval, -20.79 to -0.47 g). Neither maternal PFOS nor PFOA levels were consistently associated with the risk for preterm birth or low birth weight. We observed no adverse effects for maternal PFOS or PFOA levels on small for gestational age.

CONCLUSION

Our nationwide cohort data suggest an inverse association between maternal plasma PFOA levels and birth weight. Because of widespread exposure to these chemicals, our findings may be of potential public health concern.

Formaldehyde and cancer risk: a quantitative review of cohort studies through 2006

BACKGROUND

Occupational exposure to formaldehyde has been associated with excess risk of nasopharyngeal and selected other cancers.

PATIENTS AND METHODS

We reviewed and pooled the results of cohort studies published through February 2007.

RESULTS

There were 5651 deaths from all cancers observed in six cohorts of industry workers and six of professionals, with a pooled relative risk (RR) of 0.95 for industry workers and of 0.87 for professionals. Nine deaths from nasopharyngeal cancer in three cohorts of industry workers yielded a pooled RR of 1.33, which declined to 0.49 after excluding six cases from one US plant. The pooled RR for lung cancer was 1.06 in industry workers and 0.63 in professionals. Corresponding values were 1.09 and 0.96 for oral and pharyngeal, 0.92 and 1.56 for brain, 0.85 and 1.31 for all lymphatic and hematopoietic cancers, and 0.90 and 1.39 for leukemia.

CONCLUSIONS

Comprehensive review of cancer in industry workers and professionals exposed to formaldehyde shows no appreciable excess risk for oral and pharyngeal, sinonasal or lung cancers. A non-significantly increased RR for nasopharyngeal cancer among industry workers is attributable to a cluster of deaths in a single plant. For brain cancer and lymphohematopoietic neoplasms there were modestly elevated risks in professionals, but not industry workers.

Excess Mortality From Suicide and Other External Causes of Death Among Women With Cosmetic Breast Implants

An increased rate of suicide among women with cosmetic breast implants has been consistently reported in the epidemiologic literature. We extended by 8 years the follow-up of our earlier mortality study of a nationwide cohort of 3527 Swedish women with cosmetic breast implants to examine in greater detail suicide and other causes of death. The number of deaths observed among these women was compared with the number expected among the age- and calendar-period-matched general female population of Sweden. Women with breast implants were followed for over 65,000 person-years, with a mean follow-up of 18.7 years (range, 0.1-37.8 years). Overall, 175 deaths occurred among women with breast implants versus 133.4 expected (standardized mortality ratio (SMR) = 1.3; 95% confidence interval [CI], 1.1-1.5). Among women with implants, we observed statistically significant 3-fold excesses of suicide (SMR, 3.0; 95% CI, 1.9-4.5) and deaths from alcohol or drug dependence (SMR, 3.1; 95% CI, 1.0-7.3), as well as an excess of deaths from accidents and injuries consistent with substance abuse or dependence. The increased risk of suicide was not apparent until 10 years after implantation. Deaths from cancer overall were close to expectation (SMR, 1.1; 95% CI, 0.8-1.4). Women with cosmetic implants had elevated SMRs for lung cancer and chronic respiratory disease. There was no excess of breast cancer mortality. The excess of deaths from suicides, drug and alcohol abuse and dependence, and other related causes suggests significant underlying psychiatric morbidity among these women. Thus, screening for pre-implant psychiatric morbidity and post-implant monitoring among women seeking cosmetic breast implants may be warranted.

Incidence Rates of Intra- and Extrahepatic Cholangiocarcinomas in Denmark From 1978 Through 2002

Recent studies from several countries, including the United States, have indicated that the incidence rate of intrahepatic cholangiocarcinoma is increasing while that of extrahepatic cholangiocarcinoma is decreasing. We examined whether such opposing trends could be confirmed in Danish data. We computed the nationwide Danish incidence rates of intra- and extrahepatic cholangiocarcinomas from January 1, 1978, through December 31, 2002, with data from the high-quality Danish Cancer Registry. Incidence rates were standardized to the US population in 2000. The study included 1335 patients with intrahepatic cholangiocarcinoma and 1269 with extrahepatic cholangiocarcinoma. The Danish incidence rates of intra- and extrahepatic cholangiocarcinomas were nearly identical throughout the study period. From 1978 through 2002, the incidence rate of intrahepatic cholangiocarcinoma decreased from 1.27 (95% confidence interval [CI] = 0.96 to 1.58) to 0.46 (95% CI = 0.29 to 0.62) per 100,000 people, and the rate of extrahepatic cholangiocarcinoma decreased from 1.05 (95% CI = 0.77 to 1.34) to 0.74 (95% CI = 0.53 to 0.95). The median age at diagnosis decreased during the study period, and the proportion of localized cancers increased. The decrease in cholangiocarcinoma incidence rates cannot be explained by time trends in known risk factors (e.g., inflammatory bowel disease, diabetes, smoking, or thorotrast), but our findings are consistent with a common etiology for intra- and extrahepatic cholangiocarcinomas.

A Nationwide Study of Connective Tissue Disease and Other Rheumatic Conditions Among Danish Women With Long-Term Cosmetic Breast Implantation

PURPOSE

Numerous epidemiologic studies have demonstrated that breast implants are not associated with connective tissue diseases (CTDs). However, many CTDs are rare, and continued follow-up of women with breast implants is warranted.

METHODS

We extended by 5 years the follow-up of our earlier population-based cohort study of Danish women with cosmetic breast implants (n = 2761) and comparison groups of women with other types of cosmetic surgery (n = 8807). All women were followed from January 1977 through December 2001. Hospitalization and outpatient data for CTD and ill-defined and other rheumatic conditions in the implant and comparison groups were compared with those in the general Danish population. Additionally, CTDs and fibromyalgia were confirmed through medical chart review, and direct comparisons of the breast implant cohort with the comparison cohort were performed.

RESULTS

When compared with general population rates, CTDs were not statistically significantly elevated in either the implant or the comparison cohorts. However, unspecified rheumatism was similarly increased in the implant (standardized rate ratio = 1.9; 95% confidence interval = 1.6 to 2.2) and comparison (standardized rate ratio = 1.5; 95% confidence interval = 1.4 to 1.7) cohorts. In analyses of diagnoses validated by chart review, women with cosmetic breast implants compared with those having other types of plastic surgery or consultation for plastic surgery had no statistically significant excess for any specific confirmed CTD or combined CTDs (hazard ratio = 1.3; 95% CI = 0.9 to 1.9). In addition, there was no relation between breast implants and confirmed fibromyalgia (hazard ratio = 1.2; 95% CI = 0.6 to 2.1).

CONCLUSIONS

This extension of our earlier cohort study further supports the consensus of epidemiologic research that breast implants are unrelated to the development of CTD.

Risk of soft tissue sarcomas by individual subtype in survivors of hereditary retinoblastoma

BACKGROUND

Survivors of hereditary retinoblastoma have an increased risk for second malignancies, especially soft tissue sarcomas. However, the risks of individual histologic subtypes of soft tissue sarcomas have not been evaluated.

METHODS

We estimated the risk for six subtypes of soft tissue sarcomas (fibrosarcoma, liposarcoma, histiocytoma, leiomyosarcoma, rhabdomyosarcoma, and others) in a cohort of 963 one-year survivors of hereditary retinoblastoma among patients diagnosed at two US institutions from 1914 through 1984. We calculated standardized incidence ratios (SIRs) for specific subtypes of soft tissue sarcomas by comparison with population data from the Connecticut Tumor Registry or from National Cancer Institute Surveillance, Epidemiology, and End Results database. We also calculated the cumulative risk for all soft tissue sarcomas combined.

RESULTS

We observed 69 soft tissue sarcomas in 68 patients with hereditary retinoblastoma. Risks were elevated for soft tissue sarcomas overall (SIR = 184, 95% confidence interval [CI] = 143 to 233) and for individual subtypes. Leiomyosarcoma was the most frequent subtype (SIR = 390, 95% CI = 247 to 585), with 78% of leiomyosarcomas diagnosed 30 or more years after the retinoblastoma diagnosis (SIR = 435, 95% CI = 258 to 687). Among patients treated with radiotherapy for retinoblastoma, we found statistically significantly increased risks of soft tissue sarcomas in the field of radiation. Irradiated patients also had increased risks of soft tissue sarcomas, especially leiomyosarcomas, outside the field of radiation, and risks of soft tissue sarcomas were increased in nonirradiated patients as well, indicating a genetic predisposition to soft tissue sarcomas independent of radiation. The cumulative risk for any soft tissue sarcoma 50 years after radiotherapy for retinoblastoma was 13.1% (95% CI = 9.7% to 17.0%).

CONCLUSION

Long-term follow-up of a cohort of survivors of hereditary retinoblastoma revealed a statistically significant excess of leiomyosarcoma and other soft tissue sarcomas that persists decades after the retinoblastoma diagnosis. Retinoblastoma survivors should undergo regular medical surveillance for sarcomas in their adult years.

The epidemiology of renal cell carcinoma

PURPOSE

We identified and examined risk factors for renal cell cancer, some of which may explain in part the trends of steadily increasing incidence rates, particularly in black Americans.

MATERIALS AND METHODS

Epidemiological studies were identified through a MEDLINE(R) search of the literature through February 2006. A qualitative summary of the results of individual studies is presented.

RESULTS

Cigarette smoking and obesity are the most consistently established causal risk factors, accounting for about 20% and 30% of renal cell cancers, respectively. Hypertension appears to independently influence renal cell cancer risk. Neither acetaminophen nor other analgesics have been convincingly linked with renal cell cancer. With respect to diet a general protective effect of fruit and vegetable consumption is the only consistently reported finding. For occupational factors the weight of the evidence provides no consistent support for the hypotheses that renal cell cancer may be caused by asbestos, gasoline or trichloroethylene exposure. Self-reported family history is associated with 2 to 3-fold increases in risk and the major inherited forms of renal cell cancer together account for about 2% of this malignancy.

CONCLUSIONS

A further reduction in cigarette smoking, and a decrease in the rates of obesity and hypertension would likely moderate the increasing incidence of renal cell cancer. Epidemiological studies, including evaluation of gene-environment interactions, are needed to specifically identify reasons for the increasing incidence, particularly for assessing the roles of obesity and hypertension. Special attention should be focused on black Americans since their incidence rate recently increased to significantly surpass that in white Americans.

A comparison of trends in the incidence of hepatocellular carcinoma and intrahepatic cholangiocarcinoma in the United States

The incidence rates of liver cancers, both hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC), are increasing in the U.S. It is possible that the increases are related to common exposures, and if so, similar trends in incidence by gender, age, ethnicity, and calendar period, might exist. To examine this hypothesis, age-specific trends in the incidence of HCC and ICC in the Surveillance, Epidemiology and End Results program (1976-2000) were examined by year of diagnosis and year of birth. Age-period-cohort models were also fit to the data. The incidence of HCC in the most recent time period was twice as high among Black men (8.8/100,000) and women (2.6/100,000) as among White men (4.6/100,000) and women (1.2/100,000). However, between 1976 and 2000, incidence among all four ethnic- and gender-specific groups increased by >90% (White males, 123.2%; White females, 96.8%; Black males, 97.9%; Black females, 91.9%) with young White men experiencing the greatest increases (432%). In contrast, ICC rates were similar for Black (0.93/100,000) and White men (0.92/100,000), but higher for White (0.57/100,000) than Black women (0.39/100,000). Although ICC incidence increased among all groups, the increase was greatest for Black men (138.5%), followed by White men (124.4%), White women (111.1%), and Black women (85.7%) Age-period-cohort analyses of HCC revealed a significant cohort effect among younger men (45-65 years old), but not older men (65-84 years old), suggesting possible differences in etiology. In conclusion, the rates of HCC and ICC approximately doubled between 1976 and 2000. Trends by age, gender, ethnicity, and birth cohort suggest that heterogeneity exists in the factors influencing these rates.

Epidemiologic Aspects of Renal Cell Carcinoma

Renal cell cancer accounts for 2% of all new cancer cases worldwide. Incidence rates have been rising steadily around the world. In the United States, the rates have been rapidly increasing among black Americans, whose incidence rate has now surpassed that of white Americans. Cigarette smoking and obesity are the most consistently established causal risk factors, accounting for more than 20% and 30% of renal cell cancers, respectively. Hypertension, rather than antihypertensive drugs, appears to influence renal cell cancer development, although the mechanism is unknown. Analgesics have not been convincingly linked with renal cell cancer risk. In general, there appears to be a protective effect of fruit and vegetable consumption, although no particular component of diet has been clearly implicated. There are sporadic and inconsistent reports of occupations or occupational exposures being associated with this cancer. Epidemiologic studies are needed to identify reasons for the increasing incidence of renal cell cancer, with particular focus on why the incidence rate for black Americans has risen to significantly surpass that of white Americans.

Breast Cancer Trends Among Young Women in the United States

BACKGROUND

It has been suggested that exposures associated with industrialization have increased breast cancer risk among young women in recent decades in the United States despite data demonstrating declining breast cancer mortality in birth cohorts born after 1945.

METHODS

Trends for in situ and invasive breast cancer incidence rates from 1975 through 2002 among white and black U.S. women ages 20 to 49 are evaluated by decade of age using linear regression analyses.

RESULTS

Despite increasing rates of in situ breast cancer after 1980 reflecting increased use of mammography, invasive breast cancer rates declined for both white and black women under age 50. These declines are consistent with a decrease in birth cohort risk of breast cancer for women born after 1945.

CONCLUSIONS

Invasive breast cancer incidence rates are not increasing in young U.S. women despite increases in mammography and trends in known risk factors (eg, reproductive factors) that would predict increasing risk.

Tobacco Use in Adult Long-term Survivors of Retinoblastoma

A significant risk of lung cancer was identified among hereditary, but not nonhereditary, retinoblastoma (Rb) patients. Tobacco use was investigated to determine whether differences in smoking prevalence might explain the lung cancer excess and to characterize smoking patterns in adult survivors of Rb. Subjects were 441 hereditary and 395 nonhereditary 1-year survivors of Rb, age >or=18 years, who responded to a telephone survey about current health behavior, including tobacco use. Response rates were 76% for hereditary and 73% for nonhereditary survivors. We compared patterns and predictors of current tobacco use among hereditary and nonhereditary survivors with other childhood cancer survivor studies and the U.S. population. Hereditary Rb survivors currently smoke cigarettes significantly less frequently than nonhereditary survivors (16. 8% versus 24.3%), although among current smokers, age at smoking initiation (17 years old) and average cigarettes (1.5 packs) smoked daily are similar. Predictors of current and ever cigarette smoking include nonhereditary Rb, older age, being female, less education, and use of other tobacco products. Rb survivors smoke cigarettes significantly less than the U.S. population (rate ratio, 0.63; 95% confidence interval, 0.5-0.8 for males; rate ratio, 0.75; 95% confidence interval, 0.6-0.9 for females), but Rb survivors have comparable smoking rates with other childhood cancer survivors. Smoking did not account for the increased risk of lung cancer among hereditary Rb patients, and this may point to an enhanced sensitivity to the carcinogenic effects of tobacco. Adult survivors of Rb should be encouraged to stop smoking.

Long-Term Cancer Risk Among Swedish Women With Cosmetic Breast Implants: An Update of a Nationwide Study

Epidemiologic evidence does not support a consistently increased cancer risk among women with cosmetic breast implants, but few studies have assessed risk beyond 15 years. Swedish women who underwent cosmetic breast implantation for the first time between January 1, 1965, and December 31, 1993 (N = 3486), were followed through December 31, 2002. Cancer incidence was ascertained through the nationwide Swedish Cancer Registry. Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) were calculated to compare cancer incidence of women with implants with women in the general population. Mean follow-up among women with breast implants was 18.4 years (range = 0.1-37.8 years). The incidence of breast cancer was below expectation (SIR = 0.7, 95% CI = 0.6 to 1.0), whereas lung cancer was above expectation (SIR = 2.2, 95% CI = 1.3 to 3.4). With respect to cancer overall and all other specific cancer sites, including brain cancer and sarcoma, non-Hodgkin lymphoma, and multiple myeloma, no statistically significantly increased or decreased SIRs were observed. Stratification by duration of follow-up revealed no statistically significantly increased or decreased SIR, with the exception of a two- to threefold excess of lung cancer among women followed for more than 15 years, which would be expected due to the high prevalence of smoking among the Swedish women with implants in our study.

A nationwide epidemiologic study of breast cancer incidence following breast reduction surgery in a large cohort of Swedish women

While it has been demonstrated that prophylactic mastectomy reduces breast cancer incidence among women at high risk, many women often consider this disfiguring surgery unacceptable. One alternative approach may be breast reduction surgery. In order to evaluate the long-term incidence of breast cancer following surgical removal of breast tissue, we have extended by 9 years the follow-up period of our earlier retrospective cohort study of Swedish women electing cosmetic breast reduction surgery (n=30,444) between 1965 and 1993, yielding an average of nearly 16 years of follow-up. Cancer incidence through 2002 was ascertained via the Swedish Cancer Registry. Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) were calculated comparing women who underwent breast reduction surgery with women in the general Swedish population. Breast cancer was observed in 443 women versus 624 expected for a statistically significant reduced SIR of 0.71 (95% CI=0.65-0.78). Analyses by age at surgery, time since surgery or calendar year of surgery revealed similar reductions in risk. Our study of over 30,000 women with long-term follow-up offers further evidence that women undergoing breast reduction surgery have reduced breast cancer risk. As the evidence from large-scale cohort studies accumulates, direct testing of this reduction in risk through clinical trials should be considered.