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Biomedical subjects

W H Chow

Publications and source records attributed to W H Chow.

At least 73 records · Page 4Linked to original sources
PubMed1998

Colorectal cancer incidence trends by subsite in urban Shanghai, 1972-1994.

Epidemiological characteristics of colorectal cancer may differ by particular anatomical subsite, suggesting that the subsite-specific colorectal cancers may represent different disease entities. This study explored the time trends over a 23-year period in colorectal cancer incidence at various subsites by sex and age group. Data on the incidence of colorectal cancer were obtained from a population-based cancer registry in Shanghai, People's Republic of China. Between 1972 and 1994, 30,693 patients with colorectal cancer were registered at the Shanghai Cancer Registry. The overall age-adjusted colorectal cancer incidence rates increased > 50%, or 2% per year from 1972-1977 to 1990-1994, from 14 to 22 per 100,000 among men and from 12 to 19 per 100,000 among women. The increases in rates were considerably more rapid for colon cancer, with rates approximately doubling, than they were for rectal cancer. Proximal colon cancer was more common than distal colon cancer over the whole study period, whereas rates for both cancers rose with similar annual percentage changes (> 5% per year) and across virtually all age groups. The estimated annual increases rose from 2% at ages 35-44 years to 7% at ages 75-84 years for proximal colon cancer, but they were more uniform for distal colon cancer (5-6% per year). Age-adjusted and age-specific rectal cancer rates changed little. The male:female age-adjusted rate ratio for colorectal cancer was 1.19 in 1990-1994. The ratios increased over time and varied by subsites, with ratios increasing from the proximal colon to the distal colon and to the rectum. Furthermore, men had higher rates than women for distal colon and rectal cancers at ages 55 and older, whereas women had higher rates than men at younger ages for these two cancers. Male:female rate ratios for proximal colon cancer did not vary substantially with age. The findings from this study indicate that subsite-specific incidence rates of colorectal cancer differ by sex and age and in their time trends. Cancers arising in the proximal colon, distal colon, and rectum may have somewhat different disease etiologies.

Adult↗
PubMed1998

Risk of esophageal and gastric adenocarcinomas in relation to use of calcium channel blockers, asthma drugs, and other medications that promote gastroesophageal reflux.

Incidence of adenocarcinomas of the esophagus and gastric cardia has risen dramatically over the past 2 decades in the U. S., for reasons that are not yet clear. A number of common medications (e.g., calcium channel blockers, tricyclic antidepressants, and certain asthma medications) promote gastroesophageal reflux by relaxing the lower esophageal sphincter (LES). Reflux is thought to increase cancer risk by promoting cellular proliferation, and by exposing the esophageal epithelium to potentially genotoxic gastric and intestinal contents. Recent studies have suggested that calcium channel blockers may also increase cancer risk by inhibiting apoptosis. Using personal interview data from a multicenter, population-based case-control study conducted between 1993 and 1995 in three areas of the U. S., we evaluated whether the use of LES-relaxing drugs was associated with increased risk of adenocarcinomas of the esophagus and gastric cardia. Cases of esophageal adenocarcinoma (n = 293) and gastric cardia adenocarcinoma (n = 261) were compared with general population controls (n = 695). Information on additional case groups of esophageal squamous cell carcinoma (n = 221) and noncardia gastric cancer (n = 368) were also available for comparison. Overall, 27.4% of controls had used one or more of these drugs for at least 6 months, compared with 30.2% of esophageal adenocarcinoma and 23.8% of gastric cardia adenocarcinoma cases. The adjusted odds ratios (ORs) for ever use were 1.0 [95% confidence interval (CI) = 0.7-1.5] and 0.8 (95% CI = 0.5-1.1), respectively. There was little evidence of increasing risk with increasing duration of use of all LES-relaxing drugs together. We found an increased risk of esophageal adenocarcinoma among persons reporting use of asthma drugs containing theophylline (OR = 2.5; 95% CI = 1.1-5.6) or beta agonists (OR = 1.7; 95% CI = 0.8-3.8). Risks were higher among long-term users (>5 years) of these drugs (OR = 3.1; 95% CI = 0.9-10.3 and OR = 2.3; 95% CI = 0.8-7.0, respectively). In contrast, there was no evidence that the use of calcium channel blockers or other specific groups of drugs increased the risk of any of the cancers studied. These results provide reassuring evidence that the increases in incidence of adenocarcinomas of the esophagus and gastric cardia are not likely to be related to the use of LES-relaxing drugs as a group, or calcium channel blockers in particular, but they do suggest that persons treated for long-standing asthma may be at increased risk of esophageal adenocarcinoma.

Adenocarcinoma↗
PubMed1997

Validation of benzene exposure assessment.

We conducted a methodologic study to validate a quantitative retrospective exposure assessment method used in a follow-up study of workers exposed to benzene. Assessment of exposure to benzene was carried out in 672 factories in 12 cities in China. Historical exposure data were collected for 3179 unique job titles. The basic unit for exposure assessment was a factory/work-unit/job-title combination over seven periods between 1949 and 1987. A total of 18,435 exposure estimates was developed, using all available historical information, including 8477 monitoring data. Overall, 38% of the estimates were based on benzene monitoring data. The highest time-weighted average exposures occurred in the rubber industry (30.7 ppm), particularly for rubber glue applicators (52.6 ppm). Because of its recognized link with benzene exposure, the association between a clinical diagnosis of benzene poisoning (hematotoxicity) and benzene exposure was evaluated (412 cases and 614,509 person-years) to validate the exposure-assessment method. Relative risks of benzene hematotoxicity increased very sharply with increasing estimated intensity of benzene exposure. Odds ratios were 2.2 (95% CI: 1.7-2.9), 4.7 (95% CI: 3.4-6.5), and 7.2 (95% CI: 5.3-9.8) for the intensity levels of less than 5 ppm, 5-19 ppm, 20-39 ppm, and 40 and more ppm, respectively. This sharp trend between benzene hematotoxicity and estimated exposure to benzene indicated that the exposure-estimation method used in this cancer epidemiology study is reliable.

Benzene↗
PubMed1997

Risk of urinary tract cancers following kidney or ureter stones.

BACKGROUND: A relationship has been suggested between kidney or ureter stones and the development of urinary tract cancers. In this study, a population-based cohort of patients hospitalized for kidney or ureter stones in Sweden was followed for up to 25 years to examine subsequent risks for developing renal cell, renal pelvis/ureter, or bladder cancer. METHODS: Data from the national Swedish In-patient Register and the national Swedish Cancer Registry were linked to follow 61,144 patients who were hospitalized for kidney or ureter stones from 1965 through 1983. Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) were computed on the basis of nationwide cancer incidence rates, after adjustment for age, sex, and calendar year. RESULTS: Risk of renal cell cancer was not elevated in this cohort. Significant excesses of renal pelvis/ureter cancer (SIR = 2.5; 95% CI = 1.8-3.3) and bladder cancer (SIR = 1.4; 95% CI = 1.3-1.6) were observed, but the SIRs for women were more than twice those for men. Risks varied little by age or duration of follow-up. Risks of renal pelvis/ureter cancer and bladder cancer among patients with an associated diagnosis of urinary tract infection were more than double those among patients without such infection, although the risks were significantly elevated in both groups. CONCLUSIONS: Individuals hospitalized for kidney or ureter stones are at increased risk of developing renal pelvis/ureter or bladder cancer, even beyond 10 years of follow-up. Chronic irritation and infection may play a role, since kidney or ureter stones were located on the same side of the body as the tumors in most patients with renal pelvis/ureter cancer evaluated in our study.

Adult↗
PubMed1997

Cancer incidence in a population-based cohort of patients hospitalized with diabetes mellitus in Denmark.

BACKGROUND: Diabetes has been associated with an increased risk of several cancers, notably cancers of the pancreas, liver, endometrium, and kidney. Since most previous studies have involved a limited sample size or focused on specific cancer sites, we conducted a comprehensive assessment of the risk of cancer in a nationwide cohort of diabetics in Denmark. METHODS: Discharge records of 109581 individuals hospitalized with a diagnosis of diabetes from 1977 through 1989 were linked with national cancer registry records through 1993. Standardized incidence ratios (SIRs) were calculated for specific cancer sites. RESULTS: The SIRs for primary liver cancer were 4.0 (95% confidence interval [CI] = 3.5-4.6) in males and 2.1 (95% CI = 1.6-2.7) in females. These SIRs remained elevated with increasing years of follow-up and after exclusion of patients with reported risk factors (e.g., cirrhosis and hepatitis) or patients whose cancers were diagnosed at autopsy. Kidney cancer risk was also elevated, with SIRs of 1.4 (95% CI = 1.2-1.6) in males and 1.7 (95% CI = 1.4-1.9) in females. For both sexes combined, the SIR for pancreatic cancer was 2.1 (95% CI = 1.9-2.4), with a follow-up time of 1-4 years; this SIR declined to 1.3 (95% CI = 1.1-1.6) after 5-9 years of follow-up. Excess risks were also observed for biliary tract and endometrial cancers. The SIRs for kidney and endometrial cancers declined somewhat after exclusion of diabetics with reported obesity. CONCLUSIONS: Patients hospitalized with a diagnosis of diabetes appear to be at higher risk of developing cancers of the liver, biliary tract, pancreas, endometrium, and kidney. The elevated risks of endometrial and kidney cancers, however, may be confounded by obesity.

Age Distribution↗
PubMed1997

Tobacco, alcohol, and socioeconomic status and adenocarcinomas of the esophagus and gastric cardia.

BACKGROUND: Incidence rates for adenocarcinomas of the esophagus and gastric cardia have risen steeply over the last few decades. To determine risk factors for these tumors, we conducted a multicenter, population-based, case-control study. METHODS: The study included 554 subjects newly diagnosed with esophageal or gastric cardia adenocarcinomas, 589 subjects newly diagnosed with esophageal squamous cell carcinoma or other gastric adenocarcinomas, and 695 control subjects. Estimates of risk (odds ratios [ORs] and corresponding 95% confidence intervals [CIs]) were calculated for the four tumor types separately and for esophageal and gastric cardia adenocarcinomas combined. RESULTS: Risk of esophageal and gastric cardia adenocarcinomas combined was increased among current cigarette smokers (OR = 2.4; 95% = 1.7-3.4), with little reduction observed until 30 years after smoking cessation; this risk rose with increasing intensity and duration of smoking. Risk of these tumors was not related to beer (OR = 0.8; 95% CI = 0.6-1.1) or liquor (OR = 1.1; 95% CI = 0.8-1.4) consumption, but it was reduced for drinking wine (OR = 0.6; 95% CI = 0.5-0.8). Similar ORs were obtained for the development of noncardia gastric adenocarcinomas in relation to tobacco and alcohol use, but higher ORs were obtained for the development of esophageal squamous cell carcinomas. For all four tumor types, risks were higher among those with low income or education. CONCLUSIONS: Smoking is a major risk factor for esophageal and gastric cardia adenocarcinomas, accounting for approximately 40% of cases. IMPLICATIONS: Because of the long lag time before risk of these tumors is reduced among ex-smokers, smoking may affect early stage carcinogenesis. The increase in smoking prevalence during the first two thirds of this century may be reflected in the rising incidence of these tumors in the past few decades among older individuals. The recent decrease in smoking may not yet have had an impact.

Adenocarcinoma↗
PubMed1997

Amorphous silica: a review of health effects from inhalation exposure with particular reference to cancer.

Silicas and silicates are some of the most abundant compounds found naturally in the earth's crust. Excessive exposure to crystalline silicas can cause serious lung disease such as silicosis and has been associated with lung cancer in some studies, but the potential health effects of amorphous silicas (silicon dioxide without crystalline structure) have not been well studied. Results from animal studies of amorphous silicas, unlike those seen with crystalline silicas, have suggested limited and largely reversible cytotoxic and possibly fibrogenic effects associated with some forms, but data on cancer outcomes are scanty and for the most part negative. Epidemiologic investigations to date for any potential cancer risk are not informative because the effects of crystalline and amorphous silicas have not been separated. Any future epidemiologic study should attempt to clarify the health effects of amorphous silicas from those of crystalline silicas, particularly with regard to any potential for carcinogenicity.

Administration, Inhalation↗
PubMed1997

Green tea consumption and the risk of pancreatic and colorectal cancers.

The effect of green tea drinking in reducing human cancer risk is unclear, though a protective effect has been reported in numerous animal studies and several epidemiologic investigations. Herein the hypothesis that green tea consumption may reduce the risk of cancers of the colon, rectum and pancreas is examined in a large population-based case-control study conducted in Shanghai, China. Newly diagnosed cancer cases (931 colon, 884 rectum and 451 pancreas) during 1990-1993 among residents 30-74 years of age were included. Controls (n = 1,552) were selected among Shanghai residents and frequency-matched to cases by gender and age. Multivariate odds ratios (ORs) and 95% confidence intervals (CIs) of each cancer associated with green tea consumption were derived after adjustment for age, income, education and cigarette smoking. Additional adjustment for dietary items and body size was found to have minimal impact. An inverse association with each cancer was observed with increasing amount of green tea consumption, with the strongest trends for rectal and pancreatic cancers. For men, compared with non-regular tea drinkers, ORs among those in the highest tea consumption category (> or = 300 g/month) were 0.82 for colon cancer, 0.72 for rectal cancer and 0.63 for pancreatic cancer, with p values for trend being 0.38, 0.04 and 0.04, respectively. For women, the respective ORs for the highest consumption category (> or = 200 g/month) were 0.67, 0.57 and 0.53, with the respective p values for trend being 0.07, 0.001 and 0.008. Our findings provide further evidence that green tea drinking may lower the risk of colorectal and pancreatic cancers.

Adult↗
PubMed1997

Use of low molecular weight heparin in postangioplasty management.

The results of using low molecular weight heparin (LMWH) in postangioplasty management are examined. In comparison to intravenous unfractionated heparin, subcutaneous LMWH caused less groin complications and was simpler and cheaper to be administered by the medical personnel. The incidence of ischaemic complications after angioplasty including acute closure and myocardial infarction, however, remained similar and was not excessive. Subcutaneous administration of LMWH provides and alternative simple and cost-effective strategy for postangioplasty management.

Aged↗
PubMed1997

Co-existing pleomorphic and tubular basal cell adenomas of the parotid gland.

We report a hitherto undescribed case of co-existence of a pleomorphic adenoma and a tubular basal cell adenoma affecting the superficial lobe of the left parotid gland of a 53-year-old man. The histology of the pleomorphic adenoma is also of interest in that the prominent adipose metaplasia of its myxoid stroma yielded an appearance reminiscent of myxoid lipoma. The tubular basal cell adenoma showed gross cystic change, and its solid portion consisted of closely packed tubules lined by double layers of cuboidal cells with little intervening stroma. Unlike Warthin's tumour and membranous basal cell adenoma, both pleomorphic and tubular basal cell adenomas exhibit no propensity towards multicentricity or bilaterality. We, therefore, believe that their co-existence in the superficial lobe of the parotid gland of our patient is a mere coincidence rather than association.

Adenoma↗
PubMed1997

A prospective study of menopausal hormones and risk of colorectal cancer (United States)

The relation of colorectal cancer and its subsites with use of menopausal hormones was evaluated in the United States among 40,464 postmenopausal women, 41 to 80 years of age, who initially volunteered for a nationwide breast-cancer screening program and were followed for an average of 7.7 years. Ever-use of menopausal hormones was not associated with risk of total colorectal cancers (relative risk [RR] = 0.99, 95 percent confidence interval [CI] = 0.79-1.2) or cancers of the colon (RR = 1.1, CI = 0.81-1.6) or rectum (RR = 1.1, CI = 0.59-1.9). Recent hormone users, however, had a small nonsignificant reduction in risk of colorectal cancer (RR = 0.78, CI = 0.55-1.1), which was most pronounced for distal colon (RR = 0.68, CI = 0.29-1.6) and rectal tumors (RR = 0.64, CI = 0.24-1.7). No effect was observed for former hormone users, and risk generally did not vary by time since last use, type of regimen, or duration of use. However, the reduced risk for recent users was stronger for users of five or more years' duration. These data show some lowering of colorectal cancer risk among recent menopausal hormone users of long duration.

Adult↗
PubMed1997

Cancer rates among drinkers of black tea.

Studies in experimental animals have shown that compounds in tea can inhibit the process of carcinogenesis, with the beneficial effects accruing to both green and black teas. Herein epidemiologic studies around the world are reviewed to assess the rates and risks of cancer among black tea drinkers. Ecologic data suggest at most a modest benefit on total cancer, as there is considerable international variation in black tea consumption but generally small differences in overall cancer rates. Cohort studies of tea drinkers and case control studies of specific cancers show mixed results. Consistent dose-related patterns have yet to emerge, although detailed data from these studies on cancer risks according to amount and duration of black tea intake are often limited. Several investigations point to the possibility of somewhat lowered risks of digestive tract cancers among tea drinkers, but the evidence is inconclusive. Further research, especially involving populations with wide ranges of tea consumption, is needed to clarify black tea's impact on cancer risk.

Cohort Studies↗
PubMed1997

Reproductive factors, oral contraceptive use, and risk of colorectal cancer.

Multiparity and use of oral contraceptives are hypothesized to reduce risk of colorectal cancer. Among 57,529 women, 31-90 years of age, who volunteered for a nationwide breast cancer screening program from 1973 to 1980, we observed 154 pathologically confirmed cases of colon cancer and 49 cases of rectal cancer in up to 10 years of follow-up (388,555 person-years). Parity was not associated with risk of colorectal cancer [age-adjusted rate ratio for > or = 4 children vs no children = 1.0; 95% confidence interval (CI) = 0.72-1.5], although decreases in proximal colon cancer and increases in distal colon cancer were observed among parous women. The effect of parity did not vary by age at diagnosis. We found no strong or consistent association for age at menarche, age at first birth, or age at natural menopause. In addition, oral contraceptive use, reflecting mainly past use, was unrelated to risk of colorectal cancer (rate ratio = 1.0; 95% CI = 0.75-1.4). These findings do not corroborate the hypothesis that reproductive events or oral contraceptives influence the development of colorectal cancer.

Adult↗
PubMed1997

Wood dust and nasal cancer risk. A review of the evidence from North America.

In this article, biomedical literature assessing risks of nasal cancer and nonmalignant nasal pathology among woodworkers in North America is reviewed in detail and contrasted with experience from Europe and elsewhere. Exceptionally high rates of nasal adenocarcinoma have occurred among European hardwood furniture workers, but the epidemiologic evidence documents a disparity in findings between North America and Europe. Cohort studies of American wood-dust-exposed groups do not reveal excesses of nasal cancer, and wood-dust associations from US and Canadian case-control studies of nasal cancer tend not to be strong and differ across studies. Quantitative wood-dust exposure data are generally unavailable, but general dose information in European studies suggests that the excess risk of nasal cancer is associated with high levels of exposure. There is also an inconsistent association between wood-dust exposure per se and mucostasis or nasal histologic changes, and the mucostasis/metaplasia/dysplasia route to nasal cancer is still an unverified hypothesis. Considering the totality of evidence on the risk of cancer in exposed workers, it appears that wood-dust-related nasal adenocarcinoma essentially can be eliminated in Europe and its occurrence prevented in the United States if wood-dust exposures do not exceed an 8-hour time-weighted average 5 mg/m3 standard.

Adenocarcinoma↗
PubMed1997

Radiofrequency catheter ablation of left-sided accessory pathways using a transeptal technique and specialized long intravascular sheaths. Efficacy, recurrence rate and complications.

49 patients with 51 left-sided accessory pathways underwent radiofrequency catheter ablation for symptomatic supraventricular tachycardia via the transeptal route using specialised long vascular sheaths with compound curves. The procedure was successful in 45 patients (92%). The mean fluroscopic time was 22.5 +/- 15.2 mins and the mean procedure time was 1.7 +/- 0.5 hours. Pericardial tamponade occurred in 2 patients (4%) and 2 patients (4%) required switching to the retrograde transaortic route for successful ablation of the pathways. During the period of follow-up of 16.8 +/- 6.9 months, clinical recurrence occurred in 2 patients (4%). In conclusion, the transeptal route of radiofrequency catheter ablation is a useful alternative strategy to the transaortic approach with good long term results. The use of specialised sheaths may help in stabilisation of the catheter during the procedure which can generate more adequate lesions and consequently a lower recurrence rate.

Adolescent↗