Colon cancer controls versus population controls in case-control studies of occupational risk factors

Lifetime Exposure to Welding Fumes and Risk of Some Rare Cancers

We investigated the association between exposure to welding fumes and the risk of biliary tract, male breast, bone, and thymus cancer, as well as cancer of the small intestine, eye melanoma, and mycosis fungoides, among men in a European, multicenter case-control study. From 1995-1997, 644 cases and 1,959 control subjects from 7 countries were studied with respect to information on welding and potential confounders. We linked the welding histories of the participants with a measurement-based exposure matrix to calculate lifetime exposure to welding fumes. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression models, conditional on country and 5-year age groups, and adjusted for education and relevant confounders. Regular welding was associated with an increased risk of cancer of the small intestine (OR = 2.30, 95% CI: 1.17, 4.50). Lifetime exposure to welding fumes above the median of exposed controls was associated with an increased risk of cancer of the small intestine (OR = 2.00, 95% CI: 1.07, 3.72) and male breast (OR = 2.07, 95% CI: 1.14, 3.77), and some elevation in risk was apparent for bone cancer (OR = 1.92, 95% CI: 0.85, 4.34) with increasing lifetime exposure to welding fumes. Welding fumes could contribute to an increased risk of some rare cancers.

Association between pesticide exposure and colorectal cancer risk and incidence: A systematic review

BACKGROUND

Studies investigating the association between pesticide exposure and colorectal cancer (CRC) risk have been inconclusive.

OBJECTIVES

Investigate the association between pesticide exposure and CRC risk through a systematic literature review.

METHODS

CRC has the fourth-highest rate of cancer-caused death in the US after lung cancer, breast cancer in women, and prostate cancer in men. Here we have conducted a systematic literature search on studies examining the association between any pesticide exposure and CRC risk using PubMed, MEDLINE via EBSCO host, and Embase according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist.

RESULTS

Following the review, 139 articles were included for qualitative evaluation. Study participants were farmers, pesticide applicators, pesticide manufacturers, spouses of pesticide applicators, farm residents, Korean veterans of the Vietnam War, rural communities, and those who consumed food with pesticide residues. The studies' results were split between those with significant positive (39 significant results) and inverse (41 significant results) associations when comparing pesticide exposure and CRC risk.

DISCUSSION

From our literature review, we have identified a similar number of significant positive and inverse associations of pesticide exposure with CRC risk and therefore cannot conclude whether pesticide exposure has a positive or inverse association with CRC risk overall. However, certain pesticides such as terbufos, dicamba, trifluralin, S-ethyl dipropylthiocarbamate (EPTC), imazethapyr, chlorpyrifos, carbaryl, pendimethalin, and acetochlor are of great concern not only for their associated elevated risk of CRC, but also for the current legal usage in the United States (US). Aldicarb and dieldrin are of moderate concern for the positive associations with CRC risk, and also for the illegal usage or the detection on imported food products even though they have been banned in the US. Pesticides can linger in the soil, water, and air for weeks to years and, therefore, can lead to exposure to farmers, manufacturing workers, and those living in rural communities near these farms and factories. Approximately 60 million people in the US live in rural areas and all of the CRC mortality hotspots are within the rural communities. The CRC mortality rate is still increasing in the rural regions despite the overall decreasing of incidence and mortality of CRC elsewhere. Therefore, the results from this study on the relationship between pesticide exposure and CRC risk will help us to understand CRC health disparities.

Geographic clustering of cutaneous T-cell lymphoma in New Jersey: an exploratory analysis using residential histories

PURPOSE

Cutaneous T-cell lymphoma (CTCL) is a rare type of non-Hodgkin lymphoma. Previous studies have reported geographic clustering of CTCL based on the residence at the time of diagnosis. We explore geographic clustering of CTCL using both the residence at the time of diagnosis and past residences using data from the New Jersey State Cancer Registry.

METHODS

CTCL cases (n = 1,163) diagnosed between 2006-2014 were matched to colon cancer controls (n = 17,049) on sex, age, race/ethnicity, and birth year. Jacquez's Q-Statistic was used to identify temporal clustering of cases compared to controls. Geographic clustering was assessed using the Bernoulli-based scan-statistic to compare cases to controls, and the Poisson-based scan-statisic to compare the observed number of cases to the number expected based on the general population. Significant clusters (p < 0.05) were mapped, and standard incidence ratios (SIR) reported. We adjusted for diagnosis year, sex, and age.

RESULTS

The Q-statistic identified significant temporal clustering of cases based on past residences in the study area from 1992 to 2002. A cluster was detected in 1992 in Bergen County in northern New Jersey based on the Bernoulli (1992 SIR 1.84) and Poisson (1992 SIR 1.86) scan-statistics. Using the Poisson scan-statistic with the diagnosis location, we found evidence of an elevated risk in this same area, but the results were not statistically significant.

CONCLUSION

There is evidence of geographic clustering of CTCL cases in New Jersey based on past residences. Additional studies are necessary to understand the possible reasons for the excess of CTCL cases living in this specific area some 8-14 years prior to diagnosis.

Rare cancers of unknown etiology: lessons learned from a European multi-center case-control study

Rare cancers together constitute one fourth of cancers. As some rare cancers are caused by occupational exposures, a systematic search for further associations might contribute to future prevention. We undertook a European, multi-center case–control study of occupational risks for cancers of small intestine, bone sarcoma, uveal melanoma, mycosis fungoides, thymus, male biliary tract and breast. Incident cases aged 35–69 years and sex-and age-matched population/colon cancer controls were interviewed, including a complete list of jobs. Associations between occupational exposure and cancer were assessed with unconditional logistic regression controlled for sex, age, country, and known confounders, and reported as odds ratios (OR) with 95% confidence intervals (CI). Interviewed were 1053 cases, 2062 population, and 1084 colon cancer controls. Male biliary tract cancer was associated with exposure to oils with polychlorinated biphenyls; OR 2.8 (95% CI 1.3–5.9); male breast cancer with exposure to trichloroethylene; OR 1.9 (95% CI 1.1–3.3); bone sarcoma with job as a carpenter/joiner; OR 4.3 (95% CI 1.7–10.5); and uveal melanoma with job as a welder/sheet metal worker; OR 1.95 (95% CI 1.08–3.52); and cook; OR 2.4 (95% CI 1.4–4.3). A confirmatory study of printers enhanced suspicion of 1,2-dichloropropane as a risk for biliary tract cancer. Results contributed to evidence for classification of welding and 1,2-dichloropronane as human carcinogens. However, despite efforts across nine countries, for some cancer sites only about 100 cases were interviewed. The Rare Cancer Study illustrated both the strengths and limitations of explorative studies for identification of etiological leads.

A randomized trial comparing limited-excision conisation to Large Loop Excision of the Transformation Zone (LLETZ) in cervical dysplasia patients

Objective

To show noninferiority of a limited-excision (resection of the dysplastic lesion only) vs. classical Large Loop Excision of the Transformation Zone (LLETZ).

Methods

In this prospective, randomized, multicenter trial, women with human papillomavirus (HPV) positive cervical intraepithelial neoplasia grade 3 were randomized into two groups (1:1). Primary outcome was the rate of negative HPV tests after 6 months, secondary outcomes included cone size, complete resection rates as well as cytological and histological results after 6 and 12 months. A sample size of 1,000 was calculated to show noninferiority of the limited-excision compared to the LLETZ group using a noninferiority margin of 5%. Enrollment was stopped after 100 patients due to slow accrual.

Results

Patients in the limited-excision group did not show a lower number of negative HPV tests (78% [LLETZ]−80% [limited-excision]=−2%; 90% confidence interval=−15%, 12%). The limited-excision resulted in a substantially lower cone size (LLETZ: 1.97 mL vs. limited-excision: 1.02 mL; p<0.001) but higher numbers of involved margins (LLETZ: 8% vs. limited-excision: 20%). Although postoperative cytological results slightly differed, histological results were similar in both groups. One limited-excision patient received immediate re-conisation, whereas one patient in each group was scheduled for re-conisation after 6 months.

Conclusion

The limited-excision could represent a promising option to reduce the surgical extent of conisations while maintaining oncological safety. The trial was not sufficiently powered to reach statistical significance due to early termination. Nevertheless, the study provides important insights in the feasibility of a limited-excision and could serve as a pilot study for future trials.

Trial Registration

German Clinical Trials Register Identifier: DRKS00006169

Tobacco smoking and alcohol consumption as risk factors for thymoma - A European case-control study

PURPOSE

Hardly anything is known about the aetiology of thymoma. This paper presents data regarding tobacco smoking and alcohol consumption in relation to thymoma from the first case-control study performed on this rare tumour.

METHODS

A European multi-centre case-control study including incident cases aged 35-69 years with thymoma between 1995 and 1997, was conducted in seven countries. A set of controls, used in seven parallel case-control studies by the same research group was used, including population-based controls from five countries and hospital controls with colon cancer from two countries. Altogether 103 cases, accepted by a reference pathologist, 712 colon cancer controls, and 2071 population controls were interviewed.

RESULTS

Tobacco smoking was moderately related with thymoma (OR 1.4, 95% CI 0.9-2.2), and a tendency to dose-response was shown (p = 0.04), with an increased risk for heavy smokers defined as ≥41 pack-years (OR 2.1, 95% CI 1.1-3.9). A high consumption of spirits defined as ≥25 g of alcohol per day was associated with an increased risk of thymoma (OR 2.4, 95% CI 1.1-5.4), whereas no association was found with beer or wine.

CONCLUSIONS

Tobacco smoking and a high intake of spirits were indicated as risk factors for thymoma.

Occupational exposure to chlorinated and petroleum solvents and mycosis fungoides

OBJECTIVE

To evaluate the potential association between occupational exposure to chlorinated and petroleum solvents and mycosis fungoides (MF).

METHODS

A questionnaire on lifetime job history was administered to 100 patients diagnosed with MF and 2846 controls. Odds ratios (ORs) were calculated as the measure of the association between exposure to each specific solvent and MF.

RESULTS

In the total sample and in men, cases and controls did not differ in relation to exposure to any of the solvents studied. In women, an association with MF was seen for the highest level of estimated exposure to perchloroethylene (OR = 11.38; 95% confidence interval: 1.04 to 124.85) and for exposure less than the median to kerosene/fuel/gasoil (OR = 8.53; 95% confidence interval: 1.11 to 65.62).

CONCLUSIONS

These results do not provide conclusive evidence that exposure to solvents may increase risk of MF because they were not found in men.

Occupational risk factors for testicular cancer: a registry-based case-control study in Rhineland Palatinate-Germany

Objectives: Testicular cancer affects mainly men below the age of 50. An association with occupation and social status has been suggested but risk factors are not well understood. A registry-based case-control study focusing on occupation was performed in Germany.

Methods: All 348 testicular cancer cases with available gainful occupational information registered between 2000 and 2005; as well as 564 suitable controls (from a pool of other cancers) were drawn from the Cancer Registry of Rhineland-Palatinate. Unconditional logistic regression was used to compute odds ratios (OR) and associated 95% confidence intervals (CI).

Results: Slightly elevated OR were observed for technicians and related professionals (OR 1.62, 95% CI 1.00–2.63) and for clerical support workers (OR 1.71, 95% CI 1.14–2.56). This increase was highest in the age group 20–50 for technicians (OR 2.02, 95% CI 1.23–3.33) and clerks (OR 2.00, 95% CI 1.30–3.09), respectively. An association with testicular cancer was observed for no other occupation.

Conclusion: An increased risk of testicular cancer was observed for technicians and related professionals and clerical support workers. This could be related to socioeconomic status or sedentary life style, two factors that were identified in previous studies. While the feasibility of a purely registry-based study was shown, missing occupational data and the choice of cancer controls represent challenges to the validity of this approach.

The current situation on vascular cognitive impairment after ischemic stroke in Changsha

The objectives of the study were to explore the prevalence and effects of vascular cognitive impairment (VCI) among ischemic stroke patients and to provide a basis for prevention and treatment strategies. A stratified cluster random sampling method was performed, and 689 ischemic stroke patients (over 40 years of age) were enrolled. All of the patients had received a neuropsychological assessment battery to assess cognitive function and self-designed questionnaires to collect relevant information. According to the cognitive status, the patients were divided into two groups, a case group and a control group. The caregivers of the patients were given a questionnaire concerning the awareness of and attitudes toward VCI. In this study, we determined that the prevalence of VCI was 41.8%. Aging, paraventricular white matter lesion (WML), macroangiopathy, high levels of alcohol, a lack of hobbies, and excessive sleep were risk factors for vascular cognitive impairment no dementia (VCIND). A high level of education, manual-work, low level of alcohol use, regular health checks, a vegetable-based diet, and more fruit and milk were protective factors for VCIND. Living alone, hyperlipidemia, transient ischemic attack, a family history of stroke, and brain atrophy were risk factors of vascular dementia (VD). A high educational level, a vegetable-based diet, and tea were protective factors for VD. The general public awareness of VCI was found to be insufficient, and there was a prejudice toward and lack of funding for the care of VCI patients. The prevalence of VCI is high in ischemic stroke patients, and there are different impact factors at different stages. Despite the high prevalence of VCI, the general public awareness is limited. Appropriate prevention measures should be developed to reduce the prevalence of VCI.

Population versus hospital controls for case-control studies on cancers in Chinese hospitals

BACKGROUND

Correct control selection is crucial to the internal validity of case-control studies. Little information exists on differences between population and hospital controls in case-control studies on cancers in Chinese hospital setting.

METHODS

We conducted three parallel case-control studies on leukemia, breast and colorectal cancers in China between 2009 and 2010, using population and hospital controls to separately match 540 incident cases by age, gender and residency at a 1:1 ratio. Demographic and lifestyle factors were measured using a validated questionnaire in face-to-face interview. Odds ratios (ORs) and 95% confidence intervals (CIs) were obtained using conditional logistic regression analyses.

RESULTS

The two control groups had closely similar exposure distributions of 15 out of 16 factors, with the only exception being that hospital controls were less likely to have a BMI ≥ 25 (OR = 0.71, 95% CI: 0.54, 0.93). For exposure of green tea drinking, the adjusted ORs (95% CIs) comparing green tealeaves intake ≥ 1000 grams annually with non-drinkers were 0.51 (0.31, 0.83) and 0.21 (0.27, 0.74) for three cancers combined, 0.06 (0.01, 0.61) and 0.07 (0.01, 0.47) for breast cancer, 0.52 (0.29, 0.94) and 0.45 (0.25, 0.82) for colorectal cancer, 0.65 (0.08, 5.63) and 0.57 (0.07, 4.79) for leukemia using hospital and population controls respectively.

CONCLUSIONS

The study found that hospital controls were comparable with population controls for most demographic characteristics and lifestyle factors measured, but there was a slight difference between the two control groups. Hospital outpatients provide a satisfactory control group in hospital-based case-control study in the Chinese hospital setting.

Cancer risk among residents of Rhineland-Palatinate winegrowing communities: a cancer-registry based ecological study

Aim

To investigate the cancer risk among residents of Rhineland-Palatinate winegrowing communities in an ecological study.

Methods

On the basis of the Rhineland-Palatinate cancer-registry, we calculated age-adjusted incidence rate ratios for communities with a medium area under wine cultivation (>5 to 20 percent) and a large area under wine cultivation (>20 percent) in comparison with communities with a small area under wine cultivation (>0 to 5 percent). In a side analysis, standardized cancer incidence ratios (SIR) were computed separately for winegrowing communities with small, medium and large area under wine cultivation using estimated German incidence rates as reference.

Results

A statistically significant positive association with the extent of viniculture can be observed for non-melanoma skin cancer in both males and females, and additionally for prostate cancer, bladder cancer, and non-Hodgkin lymphoma in males, but not in females. Lung cancer risk is significantly reduced in communities with a large area under cultivation. In the side-analysis, elevated SIR for endocrine-related tumors of the breast, testis, prostate, and endometrium were observed.

Conclusion

This study points to a potentially increased risk of skin cancer, bladder cancer, and endocrine-mediated tumors in Rhineland-Palatinate winegrowing communities. However, due to the explorative ecologic study design and the problem of multiple testing, these findings are not conclusve for a causal relationship.

Pesticide use and colorectal cancer risk in the Agricultural Health Study

We investigated the relationship between agricultural pesticides and colorectal cancer incidence in the Agricultural Health Study. A total of 56,813 pesticide applicators with no prior history of colorectal cancer were included in this analysis. Detailed pesticide exposure and other information were obtained from self-administered questionnaires completed at the time of enrollment (1993-1997). Cancer incidence was determined through population-based cancer registries from enrollment through December 31, 2002. A total of 305 incident colorectal cancers (212 colon, 93 rectum) were diagnosed during the study period, 1993-2002. Although most of the 50 pesticides studied were not associated with colorectal cancer risk, chlorpyrifos use showed significant exposure response trend (p for trend = 0.008) for rectal cancer, rising to a 2.7-fold (95% confidence interval: 1.2-6.4) increased risk in the highest exposure category. Aldicarb was associated with a significantly increased risk of colon cancer (p for trend = 0.001), based on a small number of exposed cases, with the highest exposure category resulting in a 4.1-fold increased risk (95% confidence interval: 1.3-12.8). In contrast, dichlorophenoxyacetic acid showed a significant inverse association with colon cancer but the association was not monotonic. Our findings should be interpreted cautiously since the literature suggesting that pesticides are related to colorectal cancer is limited. Nonetheless the possibility of an association between exposure to certain pesticides and incidence of colorectal cancer among pesticide applicators deserves further evaluation.

Occupational factors and risk of adult bone sarcomas: a multicentric case-control study in Europe

We investigated the association between occupational factors and risk of bone sarcoma, a rare tumor with a largely unknown aetiology. A multicentric case-control study was conducted in 7 European countries in 1995-97. Ninety-six cases aged 35-69 years with a centrally reviewed diagnosis of bone sarcoma (68 chondrosarcomas and 28 osteosarcomas) were compared to 2,632 population (68%) or colon cancer (32%) controls. Subjects were interviewed to obtain information on occupational, medical and reproductive history, smoking and alcohol consumption and selected exposures including use of pesticides. Response proportions were 90% among cases and 66% among controls. Odds ratios (OR) and 95% confidence intervals (CI) were estimated for selected categories of job titles and branches of industry and for use of pesticides. We found an increased OR for bone sarcoma among blacksmiths, toolmakers, machine-tool operators (OR = 2.14, 95% CI 1.08-4.26), woodworkers (OR = 2.68, 95% CI 1.36-5.29) and construction workers (OR = 1.62, 95% CI 0.92-2.87). Ever users of pesticide had an OR of 2.33 (95% CI 1.31-4.13), with similar risks for exposure to insecticides and exposure to herbicides. Neither duration of employment in any of the analyzed occupational categories nor duration of use of pesticides showed an increasing trend in the risk of bone sarcoma. ORs of bone sarcoma were 1.03 (95% CI 0.23-4.57), 3.13 (95% CI 1.26-7.76) and 1.44 (95% CI 0.43-4.85) for the first, second and third tertile of days of use of pesticides. Our study suggests that novel and previously reported (woodworking) occupational factors play a role in the aetiology of bone sarcomas.