Work in dry cleaning and the incidence of cancer of the oral cavity, larynx, and oesophagus

NOTCH1 Intracellular Domain and the Tumor Microenvironment as Prognostic Markers in HNSCC

Simple Summary

In the head and neck, a large proportion of squamous cell carcinoma demonstrate a mutation of the NOTCH1 gene. The aim of this project was to investigate the role of NOTCH1 and immunological characteristics and highlight a potential rationale for therapy. We found that a high expression of NOTCH1 intracellular domain in these patients is associated with reduced overall survival. In vitro experiments additionally showed a reduction of migration and proliferation of cancer cells when NOTCH1 was knocked down. NOTCH1 is, therefore, most likely involved in migration and proliferation of head and neck squamous cell carcinoma and is a prognostic marker in these patients.

Abstract

(1) Background: NOTCH1 is the second most common mutated gene in whole-exome sequencing of HNSCC. The aim of this project was to gain further insight into the relevance of NOTCH1 in HNSCC, potentially establishing NOTCH1 as a prognostic marker or therapeutic target; (2) Methods: NOTCH1 was silenced via RNA interference in six HNSCC cell lines and the impact was evaluated in migration and proliferation assays. Subsequently, the protein expression of NOTCH1 intracellular domain (NICD) and NOTCH1 mRNA expression were examined in 70 oropharyngeal squamous cell cancer tissue samples. Lastly, the NICD expression was compared with the local infiltration of lymphocytes, measured with the immunoscore; (3) Results: Knockdown of NOTCH1 decreased migration and proliferation. A high NICD expression was associated with lower OS. A high immunoscore resulted in significantly better OS. NICD expression was independent of the immunoscore and as a whole differentiated three distinct prognostic groups; (4) Conclusions: These data suggest that NOTCH1 is involved in migration and proliferation of HNSCC cell lines. In vivo, NICD expression was associated with overall survival and could, therefore, be used as a prognostic marker. NICD expression differs from NOTCH1 mRNA levels, potentially explaining the previously suggested bimodal role as an oncogene and tumor suppressor in HNSCC.

A robust and interpretable gene signature for predicting the lymph node status of primary T1/T2 oral cavity squamous cell carcinoma

Oral cavity squamous cell carcinoma (OSCC) affects more than 30 000 individuals in the United States annually, with smoking and alcohol consumption being the main risk factors. Management of early-stage tumors usually includes surgical resection followed by postoperative radiotherapy in certain cases. The cervical lymph nodes (LNs) are the most common site for local metastasis, and elective neck dissection is usually performed if the primary tumor thickness is greater than 3.5 mm. However, postoperative histological examination often reveals that many patients with early-stage disease are negative for neck nodal metastasis, posing a pressing need for improved risk stratification to either avoid overtreatment or prevent the disease progression. To this end, we aimed to identify a primary tumor gene signature that can accurately predict cervical LN metastasis in patients with early-stage OSCC. Using gene expression profiles from 189 samples, we trained K-top scoring pairs models and identified six gene pairs that can distinguish primary tumors with nodal metastasis from those without metastasis. The signature was further validated on an independent cohort of 35 patients using real-time polymerase chain reaction (PCR) in which it achieved an area under the receiver operating characteristic (ROC) curve and accuracy of 90% and 91%, respectively. These results indicate that such signature holds promise as a quick and cost effective method for detecting patients at high risk of developing cervical LN metastasis, and may be potentially used to guide the neck treatment regimen in early-stage OSCC.

Perspectives in Head and Neck Medical Oncology

The modern treatment of locoregionally advanced disease often requires a multimodality combination approach. A number of chemotherapeutic agents can be combined with radiation, but the platinum agent cisplatin, a potent radiation sensitizer, is best studied in head and neck cancer. Newer agents such as cetuximab can be used in combination with radiation therapy for those patients who cannot tolerate cisplatin. For chemotherapy-naïve patients with metastatic head and neck cancer who demonstrate a good performance status, platinum doublet regimens are commonly used. Doublet regimens generally improve response rates compared to single-agent chemotherapies, although they have not demonstrated a survival benefit over single agents and they have added toxicity. Immunotherapies, alternative cytotoxic chemotherapies, and targeted therapies are second-line options for patients with disease that has progressed on platinum-based therapy. Immunotherapy, in particular, has gained focus by enhancing the ability of the immune system to recognize and destroy malignant cells. When multimodal approaches are used, as in combined chemotherapy and radiation therapy, toxicities are increased. It is imperative that patients are followed closely in order to maximize treatment benefit while minimizing complications.

Occupational exposure to chlorinated solvents and risk of head and neck cancer in men: a population-based case-control study in France

BACKGROUND

Few epidemiological studies have investigated the link between occupational exposure to solvents and head and neck cancer risk, and available findings are sparse and inconsistent. The objective of this study was to examine the association between occupational exposure to chlorinated solvents and head and neck cancer risk.

METHODS

We analyzed data from 4637 men (1857 cases and 2780 controls) included in a population-based case-control study, ICARE (France). Occupational exposure to five chlorinated solvents (perchloroethylene [PCE], trichloroethylene [TCE], methylene chloride [MC], chloroform [CF], and carbon tetrachloride [CT]) was assessed through job-exposure matrices. Odds ratios (ORs) and confidence intervals (95% CI) were estimated by unconditional logistic regression, adjusted for age, tobacco smoking, alcohol consumption, asbestos exposure, and other potential confounders.

RESULTS

We observed no association between chlorinated solvent exposure and head and neck cancer risk, despite a non-significant increase in risk among subjects who had the highest cumulative level of exposure to PCE, (OR = 1.81; 95% CI = 0.68 to 4.82). In subsite analysis, the risk of laryngeal cancer increased with cumulative exposure to PCE (p for trend = 0.04). The OR was 3.86 (95% CI = 1.30 to 11.48) for those exposed to the highest levels of PCE. A non-significant elevated risk of hypopharyngeal cancer was also observed in subjects exposed to the highest levels of MC (OR = 2.36; 95% CI = 0.98 to 5.85).

CONCLUSION

Our findings provide evidence that high exposure to PCE increases the risk of laryngeal cancer, and suggest an association between exposure to MC and hypopharyngeal cancer. Exposure to other chlorinated solvents was not associated with the risk of head and neck cancer.

Occupational exposure to solvents and risk of head and neck cancer in women: a population-based case-control study in France

OBJECTIVE

Our objective was to investigate the association between head and neck cancer and occupational exposure to chlorinated, oxygenated and petroleum solvents in women.

METHODS

Investigation of occupational and environmental CAuses of REspiratory cancers (ICARE), a French population-based case-control study, included 296 squamous cell carcinomas of the head and neck (HNSCC) in women and 775 female controls. Lifelong occupational history was collected. Job-exposure matrices allowed to assess exposure to 5 chlorinated solvents (carbon tetrachloride; chloroform; methylene chloride; perchloroethylene; trichloroethylene), 5 petroleum solvents (benzene; special petroleum product; gasoline; white spirits and other light aromatic mixtures; diesel, fuels and kerosene) and 5 oxygenated solvents (alcohols; ketones and esters; ethylene glycol; diethyl ether; tetrahydrofuran). OR and 95% CIs, adjusted for smoking, alcohol drinking, age and geographical area, were estimated with logistic models.

RESULTS

Elevated ORs were observed among women ever exposed to perchloroethylene (OR=2.97, 95% CI 1.05 to 8.45) and trichloroethylene (OR=2.15, 95% CI 1.21 to 3.81). These ORs increased with exposure duration (OR=3.75, 95% CI 0.64 to 21.9 and OR=4.44, 95% CI 1.56 to 12.6 for 10 years or more, respectively). No significantly increased risk of HNSCC was found for occupational exposure to the other chlorinated, petroleum or oxygenated solvents.

CONCLUSIONS

These findings suggest that exposure to perchloroethylene or trichloroethylene may increase the risk of HNSCC in women. In our study, there is no clear evidence that the other studied solvents are risk factors for HNSCC.

Occupation and head and neck cancer in women-Results of the ICARE study

BACKGROUND

Few occupational studies have addressed head and neck cancer, and these studies have been predominantly conducted in men. Accordingly, our objective was to investigate the association between head and neck cancer and occupation in women.

METHODS

ICARE, a French population-based case-control study, included 296 squamous cell carcinomas of the head and neck in women and 775 controls. Lifelong occupational history was collected. Odds ratios (ORs) and 95% confidence intervals (CI), adjusted for smoking, alcohol drinking and education level, were estimated for occupations and industries.

RESULTS

An elevated OR was observed for working proprietors working for 10 years or more (OR = 3.83, 95% CI: 1.12-13.0) with a significant trend with duration of employment (P = 0.047). Elevated but non-significant ORs were observed for street vendors (OR = 3.76, 95% CI: 0.99-14.3, P for trend = 0.13), bakers (OR = 4.19, 95% CI: 0.63-27.9, P for trend = 0.06), and welders and flame cutters (OR = 2.18, 95% CI: 0.33-14.4, P for trend = 0.05).

CONCLUSIONS

This exploratory study suggests a role of occupational exposures in the development of HN cancer in women. Further investigations of exposures to specific agents are needed.

A review of risk factors for oral cavity cancer: the importance of a standardized case definition

The aim of this work is to review the literature on risk factors of oral cavity cancer with a special attention to the definition of the cases, in order to highlight special features of these cancers and of their subsites. PubMed database was systematically searched to access relevant articles published between 1980 and 2010. Reference lists of selected papers were examined to identify further articles. One hundred and two studies met the inclusion criteria. Their results were difficult to compare because of the lack of uniformity in defining oral cavity. In addition, few studies examined risk factors other than alcohol and tobacco, and studies differentiating between subsites were rare. Despite these limitations, some characteristics of oral cavity cancers may be emphasized: smoked tobacco seems to be a stronger risk factor for oral cavity cancer than alcohol, and the floor of the mouth seems to be more sensitive to the harmful effects of alcohol and smoked tobacco. Studies limited strictly to oral cavity cancers and distinguishing between subsites are needed to better understand the aetiology of these cancers, and better define risk groups to target prevention efforts and screening.

History of diabetes and risk of head and neck cancer: a pooled analysis from the international head and neck cancer epidemiology consortium

BACKGROUND

A history of diabetes is associated with an increased risk of several types of cancers. Whether diabetes is a risk factor for head and neck cancer (HNC) has received little attention.

METHODS

We pooled data from 12 case-control studies including 6,448 cases and 13,747 controls, and estimated OR and 95% CI for the associations between diabetes and HNC, adjusted for age, education level, sex, race/ethnicity, study center, cigarette smoking, alcohol use, and body mass index.

RESULTS

We observed a weak association between diabetes and the incidence of HNC overall (OR, 1.09; 95% CI: 0.95-1.24). However, we observed a modest association among never smokers (OR, 1.59; 95% CI: 1.22-2.07), and no association among ever smokers (OR, 0.96; 95% CI: 0.83-1.11); likelihood ratio test for interaction P = 0.001.

CONCLUSION

A history of diabetes was weakly associated with HNC overall, but we observed evidence of effect modification by smoking status, with a positive association among those who never smoked cigarettes.

IMPACT

This study suggests that glucose metabolism abnormalities may be a HNC risk factor in subgroups of the population. Prospective studies incorporating biomarkers are needed to improve our understanding of the relationship between diabetes and HNC risk, possibly providing new strategies in the prevention of HNC.

Investigation of occupational and environmental causes of respiratory cancers (ICARE): a multicenter, population-based case-control study in France

BACKGROUND

Occupational causes of respiratory cancers need to be further investigated: the role of occupational exposures in the aetiology of head and neck cancers remains largely unknown, and there are still substantial uncertainties for a number of suspected lung carcinogens. The main objective of the study is to examine occupational risk factors for lung and head and neck cancers.

METHODS/DESIGN

ICARE is a multi-center, population-based case-control study, which included a group of 2926 lung cancer cases, a group of 2415 head and neck cancer cases, and a common control group of 3555 subjects. Incident cases were identified in collaboration with cancer registries, in 10 geographical areas. The control group was a random sample of the population of these areas, with a distribution by sex and age comparable to that of the cases, and a distribution by socioeconomic status comparable to that of the population. Subjects were interviewed face to face, using a standardized questionnaire collecting particularly information on tobacco and alcohol consumption, residential history and a detailed description of occupational history. Biological samples were also collected from study subjects. The main occupational exposures of interest are asbestos, man-made mineral fibers, formaldehyde, polycyclic aromatic hydrocarbons, chromium and nickel compounds, arsenic, wood dust, textile dust, solvents, strong acids, cutting fluids, silica, diesel fumes, welding fumes. The complete list of exposures of interest includes more than 60 substances. Occupational exposure assessment will use several complementary methods: case-by-case evaluation of exposure by experts; development and use of algorithms to assess exposure from the questionnaires; application of job-exposure matrices.

DISCUSSION

The large number of subjects should allow to uncover exposures associated with moderate increase in risks, and to evaluate risks associated with infrequent or widely dispersed exposures. It will be possible to study joint effects of exposure to different occupational risk factors, to examine the interactions between occupational exposures, tobacco smoking, alcohol drinking, and genetic risk factors, and to estimate the proportion of respiratory cancers attributable to occupational exposures in France. In addition, information on many non-occupational risk factors is available, and the study will provide an excellent framework for numerous studies in various fields.

Require safer substitutes and solutions: making the substitution principle the cornerstone of sustainable chemical policies

Currently, chemical regulations in the United States do not prioritize the production and use of inherently safe chemicals. At present, when regulations get passed to target a chemical for control, safer substitutes are not the goal nor are there specific guidelines or tools used to achieve Green Chemistry, Clean Production, or sustainable product design. In most cases, the replacement is often just as hazardous or simply a reduction of the quantity or concentration of the toxic substance that has been targeted. In contrast, by placing the Substitution Principle at the heart of new chemical policies and regulations, hazardous chemicals would be replaced with less hazardous alternatives or preferably alternatives for which no hazards can be identified. This would hasten the uptake of Green Chemistry, or environmentally benign chemical synthesis. Substituting hazardous chemicals goes beyond finding a drop-in chemical alternative and can include systems, materials or process changes. Regulatory drivers include a clear timeline for phase out of priority chemicals based on their inherent hazard, mandatory substitution planning for hazardous chemicals, financial and technical support for companies to find safer materials, and increased funding for green chemistry development and uptake by companies.

Cancer in persons working in dry cleaning in the Nordic countries

U.S. studies have reported an increased risk of esophageal and some other cancers in dry cleaners exposed to tetrachloroethylene. We investigated whether the U.S. findings could be reproduced in the Nordic countries using a series of case-control studies nested in cohorts of laundry and dry-cleaning workers identified from the 1970 censuses in Denmark, Norway, Sweden, and Finland. Dry-cleaning work in the Nordic countries during the period when tetrachloroethylene was the dominant solvent was not associated with an increased risk of esophageal cancer [rate ratio (RR) = 0.76; 95% confidence interval (CI), 0.34-1.69], but our study was hampered by some unclassifiable cases. The risks of cancer of the gastric cardia, liver, pancreas, and kidney and non-Hodgkin lymphoma were not significantly increased. Assistants in dry-cleaning shops had a borderline significant excess risk of cervical cancer not found in women directly involved in dry cleaning. We found an excess risk of bladder cancer (RR = 1.44; 95% CI, 1.07-1.93) not associated with length of employment. The finding of no excess risk of esophageal cancer in Nordic dry cleaners differs from U.S. findings. Chance, differences in level of exposure to tetrachloroethylene, and confounding may explain the findings. The overall evidence on bladder cancer in dry cleaners is equivocal.

Occupational exposures and risk of esophageal and gastric cardia cancers among male Swedish construction workers

OBJECTIVE

The rising incidence and the strong male predominance among patients with esophageal and gastric cardia adenocarcinoma remain unexplained. We hypothesized that occupational airborne exposures in a traditional male dominated industry might contribute to these observations.

METHODS

A prospective, large cohort study of Swedish construction workers was linked to the Swedish population-based registers of Cancer, Causes of Death and Total Population. 260,052 men were followed from 1971 through 2000. Industrial hygienists assessed specific exposures for 200 job titles, and occupational airborne exposures were analyzed separately and combined. Incidence rate ratios (IRR), with 95% confidence intervals (CI), were estimated in multivariable Cox regression models adjusted for attained age, calendar period, smoking status and body mass.

RESULTS

We found positive associations between high exposure to asbestos (IRR 4.5 [95% CI 1.4-14.3]) and cement dust (IRR 3.8 [95% CI 1.5-9.6]) and risk of esophageal adenocarcinoma. Associations were seen between high exposure to asphalt fumes (IRR 2.3 [95% CI 1.0-5.3]) and wood dust (IRR 4.8 [95% CI 1.2-19.4]) and risk of cardia adenocarcinoma. No consistent associations regarding esophageal squamous-cell carcinoma were found.

CONCLUSIONS

Exposure to asbestos and cement dust may be risk factors for esophageal adenocarcinoma, and exposure to asphalt fumes and wood dust may increase the risk of cardia adenocarcinoma. However, these associations cannot explain the major sex differences or the increasing incidence trends of these tumors.

Increased incidence of carcinoma of the tongue in patients with systemic sclerosis

OBJECTIVE

To describe the incidence of carcinoma of the tongue in a large cohort of patients with systemic sclerosis (SSc).

METHODS

In total, 769 patients with SSc were prospectively followed over 16 years for the development of cancer. Patients with a diagnosis of carcinoma of the tongue were identified to determine the incidence of this cancer in SSc. The results were compared to the incidence of tongue cancer in the SEER cancer registries.

RESULTS

A total of 3775 patient-years of followup of 769 patients with SSc (392 diffuse cutaneous, 377 limited cutaneous) prospectively evaluated for the occurrence of cancer disclosed 9 patients who were diagnosed with oral cavity and pharyngeal carcinomas. Six of these patients had squamous cell carcinoma of the tongue. One of these had both pharyngeal and tongue squamous cell carcinomas within a 4-year period, and another had 3 separate squamous cell carcinomas of the tongue. The standardized incidence ratio of squamous cell carcinoma of the tongue observed in this cohort of patients with SSc was 25-fold higher than that expected in an age adjusted population from the SEER cancer registries. All patients with SSc identified within this cohort with oral cavity carcinomas had the diffuse subset of the disease.

CONCLUSION

There is a highly significant increase in the incidence of squamous cell carcinoma of the tongue in patients with SSc. A remarkable observation was that all patients within this cohort who developed oral cancer had the diffuse subset of SSc. This suggests a relationship between the etiology or pathogenesis of the diffuse form of SSc and development of squamous cell carcinoma of the tongue in this group of patients.

A simple approach to performing quantitative cancer risk assessment using published results from occupational epidemiology studies

Quantitative risk assessment provides formalized scientific input for setting occupational and environmental standards for potentially toxic exposures. We describe the methods to perform quantitative cancer risk assessment based on published epidemiological literature using a hand calculator or spreadsheet. These methods are illustrated for some suspected or known human carcinogens, including perchloroethylene, formaldehyde, benzene and nickel. The approach to cancer risk assessment presented here may prove useful for those without access to original data from epidemiologic studies. The methods described should facilitate the use of published epidemiological data in the estimation of cancer risk in the general or working population.

Risk of laryngeal cancer by occupational chemical exposure in Turkey

Laryngeal cancer is the second most common cancer among men in Turkey. In this hospital based case-control study, we evaluated laryngeal cancer risks from occupational chemical exposures. We analyzed 940 laryngeal cancer cases and 1519 controls. Occupational history, tobacco, and alcohol use and demographic information were obtained by a questionnaire. The job and industries were classified by special seven-digit codes. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) based on a developed exposure matrix for chemicals, including diesel exhaust, gasoline exhaust, polycyclic aromatic hydrocarbons (PAHs), formaldehyde, and solvents. An excess of laryngeal cancer occurred with diesel exhaust (OR=1.5, 95% CI=1.3-1.9), gasoline exhaust (OR=1.6, 95% CI=1.3-2.0), and PAHs (OR=1.3, 95% CI=1.1-1.6). There was a dose-response relationship for these substances with supraglottic cancers (P<0.000). The PAH association only occurred among those who also had exposure to diesel exhaust.

Critical review of the epidemiological literature on occupational exposure to perchloroethylene and cancer

OBJECTIVES

Of an estimated 500,000 workers in the USA potentially exposed to perchloroethylene (PCE), the largest share is employed in the dry-cleaning industry. PCE, a non-flammable solvent, has commercial applications as a chemical intermediate, metal degreaser and, since the 1950s, primary solvent in the dry-cleaning industry. The International Agency for Research on Cancer (IARC) currently finds sufficient evidence to designate PCE as carcinogenic in animals, with limited evidence in humans. With regard to occupational exposure through dry-cleaning, PCE is considered to be possibly carcinogenic to humans. This review was conducted to assess the current epidemiological literature on PCE and specific cancers.

METHODS

A comprehensive search was conducted to identify all available epidemiological literature pertaining to the carcinogenic effects of PCE. Forty-four papers that provided reasonable data on up to 17 cancer sites were critically reviewed in the context of the available background literature for each cancer site and were assessed on the basis of specified methodological and scientific quality criteria.

RESULTS

While all the epidemiological studies selected for review investigated similar exposure-health outcome relationships, there was a broad diversity of proxy measurements of exposure to PCE, as well as numerous specific cancer outcomes of interest. The widespread lack of valid exposure measurements or other adequate indicators of potential for exposure were consistent limitations. We found no evidence of an association between breast, prostate, skin or brain cancer and exposure to PCE. A relationship between PCE and cancer of the following sites was considered unlikely: oral cavity, liver, pancreas, cervix lung. Scientific evidence was inadequate for laryngeal, kidney, esophageal and bladder cancers.

CONCLUSIONS

The current epidemiological evidence does not support a conclusion that occupational exposure to PCE is a risk factor for cancer of any specific site. Priority areas in which additional data are most needed include cancers of the esophagus and bladder.

Extended mortality follow-up of a cohort of dry cleaners

PURPOSE

The mortality follow-up of a cohort of dry cleaners was extended to further evaluate cancers risks associated with organic solvents.

METHODS

The underlying and contributing causes of death among 5,369 members of a dry cleaning union in St. Louis were determined through December 31, 1993. The mortality experience of the cohort was compared to that of the US population adjusted for age at entry, year of death, race and gender.

RESULTS

The total mortality was about as expected (SMR = 1.0, N = 2351, 95% CI = 1.0-1.1). Excesses were observed for emphysema (SMR = 1.7, N = 21, 95% CI = 1.0-2.5), Hodgkin's disease (SMR = 2.0, N = 5, 95% CI = 0.6-4.6) and cancers of the esophagus (SMR = 2.2, N = 26, 95% CI = 1.5-3.3), larynx (SMR = 1.7, N = 6, 95% CI = 0.6-3.7), lung (SMR = 1.4, N = 125), 95% CI = 1.1-1.6), and cervix (SMR = 1.6, N = 27, 95% CI = 1.0-2.3). These excesses occurred among men and women and blacks and whites. Bladder cancer was elevated among white men and women and kidney cancer among black men and women, but not significantly so. None of these causes of death showed strong relationships with duration or estimated level of exposure to dry cleaning solvents, although relative risks for cancers of the larynx, lung and kidney were larger among subjects estimated to have higher levels of exposure and risks from bladder cancer and chronic nephritis were greater among persons who entered the union after 1960.

CONCLUSION

The excesses observed are unlikely to be due to chance because most occurred in earlier as well as the recent follow-up. The specific factors contributing the excesses, however, are not clear. Socioeconomic, lifestyle, and occupational exposures are all possibilities. Lack of information on socioeconomic and lifestyle factors hampers evaluation.

Occupation and risk of esophageal and gastric cardia adenocarcinoma

BACKGROUND

Adenocarcinomas of the esophagus and gastric cardia have risen dramatically in incidence over the past few decades, however, little research has been conducted on the occupational risk factors for these cancers.

METHODS

In this population-based case-control study, lifetime job histories were compared between cases of esophageal adenocarcinoma (n = 283), gastric cardia adenocarcinoma (n = 259), and population controls (n = 689). Odds ratios (OR) and 95% confidence intervals (CI) for ever employment and by duration in various occupational and industrial categories were calculated using unconditional logistic regression.

RESULTS

The risk of esophageal adenocarcinoma was elevated for persons ever employed in administrative support (OR = 1.5; 95%CI = 1.0-2.1); financial, insurance, and real estate (OR = 1.6; 95%CI = 1.0-2.4); and health services (OR = 2.2; 95%CI = 1.2-3.9). The risk of gastric cardia adenocarcinoma was increased among transportation workers (OR = 1.7; 95%CI = 1.1-2.6), as well as among carpenters (OR = 1.8; 95%CI = 0.9-3.9) and workers in the furniture manufacturing industry (OR = 2.4; 95%CI = 0.9-6.3). However, we observed few duration-response relations between length of employment in any category and cancer risk.

CONCLUSIONS

This study revealed associations of esophageal adenocarcinoma with employment in administrative support, health services, and a category of financial, insurance, and real estate industries, and of gastric cardia adenocarcinoma with transportation and certain woodworking occupations. Some of these findings may be due to the play of chance associated with the multiple comparisons made in this study. Our results suggest that, overall, workplace exposures play a minor role in the etiology and upward trend of esophageal and gastric cardia adenocarcinomas.

Mortality in dry-cleaning workers: an update

BACKGROUND

A cohort of 1,708 dry-cleaning workers identified from union records was exposed to perchloroethylene (PCE), a known animal carcinogen and probable human carcinogen, for at least 1 year before 1960. Many workers also had exposure to Stoddard solvent, a petroleum-based dry-cleaning solvent.

METHODS

Vital status was updated through 1996 and life table analyses conducted.

RESULTS

The cohort had excess cancer mortality (271 deaths, standardized mortality ratio [SMR] 1.25, 95% confidence interval [CI] 1.11-1.41). Elevated SMRs for tongue, bladder, esophagus, intestine, lung, and cervical cancer, pneumonia, and diseases of the stomach and duodenum were statistically significant.

CONCLUSION

The current study confirms findings of prior updates and other studies that dry-cleaning workers have excess cancer mortality at several sites. Although important lifestyle and socioeconomic risk factors exist for both cervical and esophageal cancer mortality, excesses of these sites in the PCE only subcohort and among workers with longer duration of PCE exposure suggest an association with PCE exposure.

Trichloroethylene and cancer: epidemiologic evidence

Trichloroethylene is an organic chemical that has been used in dry cleaning, for metal degreasing, and as a solvent for oils and resins. It has been shown to cause liver and kidney cancer in experimental animals. This article reviews over 80 published papers and letters on the cancer epidemiology of people exposed to trichloroethylene. Evidence of excess cancer incidence among occupational cohorts with the most rigorous exposure assessment is found for kidney cancer (relative risk [RR] = 1.7, 95% confidence interval [CI] 1.1-2.7), liver cancer (RR = 1.9, 95% CI(1.0-3.4), and non-Hodgkin's lymphoma (RR = 1.5, 95% CI 0.9-2.3) as well as for cervical cancer, Hodgkin's disease, and multiple myeloma. However, since few studies isolate trichloroethylene exposure, results are likely confounded by exposure to other solvents and other risk factors. Although we believe that solvent exposure causes cancer in humans and that trichloroethylene likely is one of the active agents, we recommend further study to better specify the specific agents that confer this risk and to estimate the magnitude of that risk.