Tumor volumes as a predictor of response to the anti-EGFR antibody drug conjugate depatuxizumab mafadotin

Background

The adverse impact of increasing brain tumor size on the efficacy of antibody-drug conjugates (ADCs) was investigated preclinically then validated with clinical data.

Methods—Preclinical study

The impact of tumor size on ADC tumor delivery and treatment response was evaluated in an EGFR-amplified patient-derived glioblastoma (GBM) model following treatment with Depatuxizumab mafadotin (Depatux-M). Biodistribution and imaging studies correlated drug distribution with starting treatment volume and anti-tumor activity.

Methods—Clinical study

M12-356 was a Phase I study of Depatux-M in patients with GBM. Blinded volumetric analysis of baseline tumor volumes of M12-356 patients was undertaken by two reviewers and results correlated with response and survival.

Results

Preclinically, imaging and biodistribution studies showed specific and significantly higher tumor uptake of zirconium-89 labeled Depatux-M (⁸⁹Zr-Depatux-M) in mice with smaller tumor volume (~98 mm³) versus those with larger volumes (~365 mm³); concordantly, mice with tumor volumes ≤100 mm³ at treatment commencement had significantly better growth inhibition by Depatux-M (93% vs 27%, P < .001) and significantly longer overall survival (P < .0001) compared to tumors ≥400 mm³. Clinically, patients with tumor volumes <25 cm³ had significantly higher response rates (17% vs. 0%, P = .009) and longer overall survival (0.5 vs 0.89 years, P = .001) than tumors above 25 cm³.

Conclusion

Both preclinical and clinical data showed intra-tumoral concentration and efficacy of Depatux-m inversely correlated with tumor size. This finding merit further investigation with pretreatment tumor volume as a predictor for response to ADCs, in both gliomas and other solid tumors.

Global health: challenges and opportunities for Singapore

Over the past decade, global health has evolved from a buzzword to a discipline, attracting interest from governments, academic institutions and funding organisations. Global health centres, institutes and initiatives in Western countries have increased in both size and number, aided primarily by institutional backing and supportive funding mechanisms. As the rise to prominence of global health on the public health agenda also coincides with shifts in global balances of power, Asia, as well as Singapore, has an expanded role to play in supporting global health teaching and research, both in the region and throughout the world. Foundations, universities, government agencies, statutory boards and the private sector all have an important role to play in moving the global health agenda forward in Singapore. Rigorous global health training and increased funding for global health research are now timely and essential in order for global health, as a discipline, to develop within Singapore and have an impact within the region.

Meta- and pooled analysis of GSTT1 and lung cancer: a HuGE-GSEC review

Lung cancer is the most common malignancy in the Western world, and the main risk factor is tobacco smoking. Polymorphisms in metabolic genes may modulate the risk associated with environmental factors. The glutathione S-transferase theta 1 gene (GSTT1) is a particularly attractive candidate for lung cancer susceptibility because of its involvement in the metabolism of polycyclic aromatic hydrocarbons found in tobacco smoke and of other chemicals, pesticides, and industrial solvents. The frequency of the GSTT1 null genotype is lower among Caucasians (10-20%) than among Asians (50-60%). The authors present a meta- and a pooled analysis of case-control, genotype-based studies that examined the association between GSTT1 and lung cancer (34 studies, 7,629 cases and 10,087 controls for the meta-analysis; 34 studies, 7,044 cases and 10,000 controls for the pooled analysis). No association was observed between GSTT1 deletion and lung cancer for Caucasians (odds ratio (OR) = 0.99, 95% confidence interval (CI): 0.87, 1.12); for Asians, a positive association was found (OR = 1.28, 95% CI: 1.10, 1.49). In the pooled analysis, the odds ratios were not significant for either Asians (OR = 0.97, 95% CI: 0.83, 1.13) or Caucasians (OR = 1.09, 95% CI: 0.99, 1.21). No significant interaction was observed between GSTT1 and smoking on lung cancer, whereas GSTT1 appeared to modulate occupational-related lung cancer.

Heterocyclic aromatic amines in domestically prepared chicken and fish from Singapore Chinese households

Chicken and fish samples prepared by 42 Singapore Chinese in their homes were obtained. Researchers were present to collect data on raw sample weight, cooking time, maximum cooking surface temperature, and cooked sample weight. Each participant prepared one pan-fried fish sample and two pan-fried chicken samples, one marinated, one not marinated. The cooked samples were analyzed for five heterocyclic aromatic amine (HAA) mutagens, including MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline); 4,8-DiMeIQx (2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline); 7,8-DiMeIQx (2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline); PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine), and IFP (2-amino-(1,6-dimethylfuro[3,2-e]imidazo[4,5-b])pyridine). A paired Student's t-test showed that marinated chicken had lower concentrations of PhIP (p<0.05), but higher concentrations of MeIQx (p<0.05) and 4,8-DiMeIQx (p<0.001) than non-marinated chicken, and also that weight loss due to cooking was less in marinated chicken than in non-marinated chicken (p<0.001). Interestingly, the maximum cooking surface temperature was higher for fish than for either marinated or non-marinated chicken (p<0.001), yet fish was lower in 4,8-DiMeIQx per gram than marinated or non-marinated chicken (p<0.001), lower in PhIP than non-marinated chicken (p<0.05), and lost less weight due to cooking than either marinated or non-marinated chicken (p<0.001). Fish was also lower in MeIQx and 7,8-DiMeIQx than marinated chicken (p<0.05). This study provides new information on HAA content in the Singapore Chinese diet.

The reliability, validity and sensitivity to change of the Chinese version of SF-36 in oriental patients with rheumatoid arthritis

OBJECTIVE

To assess the reliability, validity and sensitivity to change of a Chinese version of the 36-item Short-Form Health Survey (SF-36) in Chinese-speaking patients with rheumatoid arthritis (RA) in Singapore.

METHODS

The psychometric properties of the Chinese Hong Kong standard version of the SF-36 were assessed in 401 RA patients. The construct validity of the Chinese SF-36 was assessed by comparison with the American College of Rheumatology (ACR) functional status, a validated Chinese Health Assessment Questionnaire (C-HAQ) and markers of RA activity and severity.

RESULTS

The overall Cronbach's coefficient alpha was 0.921, reflecting excellent internal consistency. The instrument showed reasonable test-retest reliability except in the social functioning (SF) subscale. There was a significant ceiling effect in the role physical (RP), SF and role emotional (RE) subscales and a floor effect in the RP and RE subscales. Physical function (PF) and SF were strongly correlated with C-HAQ and patient's assessment of RA activity [Pearson's correlation coefficient (r) ranging from -0.41 to -0.53] and moderately correlated with ACR functional status (r = -0.35 and -0.3, respectively). Weak correlations were also found between the Chinese SF-36 and markers of RA activity, deformed joint count and radiographic damage. PF and SF were the subscales most responsive to change in quality of life (QOL).

CONCLUSION

The Chinese SF-36 showed reasonable reliability, criterion validity and responsiveness with limitations in certain subscales. Overall, the physical domains and PF in particular may be the most ideal psychometric measures of QOL in RA.

Second primary cancers among 109 000 cases of non-Hodgkin's lymphoma

An analysis of other primary cancers in individuals with non-Hodgkin's lymphoma (NHL) can help to elucidate this cancer aetiology. In all, 109 451 first primary NHL were included in a pooled analysis of 13 cancer registries. The observed numbers of second cancers were compared to the expected numbers derived from the age-, sex-, calendar period- and registry-specific incidence rates. We also calculated the standardised incidence ratios for NHL as a second primary after other cancers. There was a 47% (95% confidence interval 43–51%) overall increase in the risk of a primary cancer after NHL. A strongly significant (P<0.001) increase was observed for cancers of the lip, tongue, oropharynx^*, stomach, small intestine, colon^*, liver, nasal cavity^*, lung, soft tissues^*, skin melanoma^*, nonmelanoma skin^*, bladder^*, kidney^*, thyroid^*, Hodgkin's lymphoma^*, lymphoid leukaemia^* and myeloid leukaemia. Non-Hodgkin's lymphoma as a second primary was increased after cancers marked with an asterisk. Patterns of risk indicate a treatment effect for lung, bladder, stomach, Hodgkin's lymphoma and myeloid leukaemia. Common risk factors may be involved for cancers of the lung, bladder, nasal cavity and for soft tissues, such as pesticides. Bidirectional effects for several cancer sites of potential viral origin argue strongly for a role for immune suppression in NHL.

Potential sources of carcinogenic heterocyclic amines in the Chinese diet: results from a 24-h dietary recall study in Singapore

OBJECTIVE

Heterocyclic amines (HCAs) from high-temperature cooking of meat have been linked to increased cancer incidence in Western populations, but data on the sources of HCAs in Asian diets are scarce. Our aim was to identify potential sources of HCAs in the Chinese diet, and to provide the basis for efforts to quantify dietary exposure to these compounds.

DESIGN AND SETTING

We conducted 24-h dietary recall interviews among 986 Chinese men and women in Singapore, who were a randomly selected subpopulation of participants from the Singapore Chinese Health Study, a population-based cohort. Details of all foods and beverages consumed by each subject in the past 24 h were recorded, and information on meat type, cooking method and portion size were abstracted from all meat-containing dishes, and gram weight equivalents computed.

RESULTS

The mean meat intake per person was 103.0 g/day (standard deviation 74.2), of which 97.2% was fresh meat. Fish (38.0%), pork (30.6%), and poultry (21.0%) accounted for 89.6% of meat consumed. Patterns of meat consumption and cooking methods differed markedly from Western populations. Documented high-temperature cooking methods, combined with stir-frying, accounted for 44.3% of fish, 35.1% of pork and 25.6% of poultry consumed. Specifically, potentially significant sources of HCAs were pan-fried fish and barbecued pork.

CONCLUSIONS

Our results identify the potential sources of HCA in the Chinese diet, highlight aspects which are relevant to HCA formation and intake, and call for novel approaches to estimating individual exposure to dietary HCAs in this and similar populations.

Trends in cancer incidence among Singapore Malays: a low-risk population

INTRODUCTION

Inspection of trends in cancer incidence in ethnically or geographically diverse populations is important for the understanding of cancer patterns and also to provide clues for aetiologic studies. There is little information on cancer incidence among Malays, a low-risk population. The population-based cancer registration system in Singapore offers the opportunity in this regard.

MATERIALS AND METHODS

A review of all newly diagnosed cancer cases among Singapore Malay residents in the period 1968 to 1997 was conducted to determine the time trends using data from Singapore Cancer Registry. Age-standardised incidence rates and average annual percentage change, using Poisson regression, were calculated.

RESULTS

During the 30-year study period, a total of 9101 incident cases of cancer were diagnosed among Malays in Singapore. The 3 most common sites of cancer were lung, liver and colorectum in males; and breast, colorectum and ovary in females in the period 1983 to 1997. Leukaemia was among the top 10 cancer sites in both sexes. Malays generally experienced lower cancer incidence rates compared to Chinese, but rates have been increasing at 1.5% to 2% annually. Statistically significant increases in incidence were observed for most of the cancer sites. The incidence of nasopharyngeal carcinoma increased, while there were no significant changes in the general population.

CONCLUSION

The relatively lower cancer risk among Singapore Malays might be attributed to genetic factors or closer adherence to a more traditional lifestyle. This study provides a baseline for comparisons with other populations with diverse cancer risk patterns in order to obtain a better understanding of possible aetiologic factors.

The Internet as a source of health information among Singaporeans: prevalence, patterns of health surfing and impact on health behaviour

OBJECTIVE

The Internet is an increasingly popular source of healthcare information. This study describes the prevalence of health surfers in Singapore and their health-surfing patterns. It also assesses their confidence in online health information and the impact the Internet has on health-seeking behaviour.

MATERIALS AND METHODS

A cross-sectional survey using a standardised questionnaire was carried out among residents aged 13 to 55 years in 1852 units in Bishan North. These units were selected by single-stage simple random cluster sampling method.

RESULTS

The household response rate was 51% (n = 950) and the individual response rate was 69% (n = 1646). Responding and non-responding households were similar in terms of ethnicity and housing type. Of the responders, 62.9% surfed the Internet and 37.7% have surfed for health information. Health surfers tended to be younger (20 to 39 years) and have higher education status. Indians were also more likely than other ethnic groups to surf for health. Professional health-related sites comprised the majority (68%) of sites visited, and the most common search keywords concern chronic degenerative diseases, e.g. hypertension. The top preferred sources of health information were doctors (25.9%), the Internet (25.3%) and the traditional mass media (20.5%). Almost half (45.1%) considered online health information trustworthy if it was from a professional source or if the website displayed the source, while 10.6% trusted the information if it concurred with the doctors' advice. The vast majority (91.7%) had taken some action in response to the information.

CONCLUSION

The Internet is being used as an accessible source of health information by a substantial proportion of the lay public. While this can facilitate greater partnership in healthcare, it underlines the need for doctors to be pro-active in the practice of evidence-based medicine, and for guidelines to enable patients to use this tool in a discerning manner.

Survival among Chinese women with lung cancer in Singapore: a comparison by stage, histology and smoking status

Lung cancer generally carries a poor prognosis and the determinants of survival have been of interest. However, survival estimates in Asian populations are scarce. This study describes survival rates and their determinants in Singapore Chinese women, a primarily non-smoking population. Three hundred and twenty-six Chinese women, diagnosed with primary lung carcinoma in three major hospitals in Singapore between April 1996 and December 1998, were followed up till 31 December 2000. The Kaplan-Meier method was used for survival analysis. Two hundred and eighty (85.7%) died from the disease during follow-up. The median survival time was 0.7 years and the three-year survival was 15.8%. These survival rates are similar to those of Western populations, and they provide a basis for examining trends over time. Age at diagnosis was an independent prognostic factor [adjusted hazard ratio (relative risk) 1.4, 95% confidence intervals (CI) 1.1-1.9 for women above 65 years relative to younger women]. Most (70.5%) tumours were stage III/IV at diagnosis. Three-year survival ranged from 72% among patients with stage I tumours to 7% for stage IV tumours. Overall, there was no survival difference among different histological types in all stages combined. When limited to stages I and II cancers, adenocarcinomas were associated with a better outcome relative to other histological subtypes combined (adjusted relative risk 0.4, 95% CI 0.1-1.0). Smoking was an independent risk factor (adjusted relative risk 1.3, 95% CI 1.0-1.8). Nevertheless, non-smokers comprised 57.4% of this series, highlighting the importance of increased awareness among health professionals and the public that lung cancer is not only a disease of smokers. The high proportion of late-stage tumours in this study and the impact of disease stage on outcome underline the importance of early detection in improving survival of lung cancer.

Dietary isothiocyanates, glutathione S-transferase -M1, -T1 polymorphisms and lung cancer risk among Chinese women in Singapore

Chinese populations consume a diet relatively high in isothiocyanates (ITCs), a derivative of cruciferous vegetables known to have cancer-protective effects. This class of compounds is metabolized by the glutathione S-transferase family of enzymes, which are also involved in the detoxification of tobacco-related carcinogens such as polycyclic aromatic hydrocarbons and alkyl halides. We evaluated the association between dietary isothiocyanate intake, GSTM1 and GSTT1 polymorphisms, and lung cancer risk in 420 Chinese women: 233 histologically confirmed lung cancer patients and 187 hospital controls. Among these, 58.8% of cases and 90.3% of controls were lifetime nonsmokers. An allele-specific PCR method was used to detect the presence or absence of the GSTM1 and GSTT1 genes in DNA isolated from peripheral blood. Higher weekly intake of ITCs (above the control median value of 53.0 micromol) reduced the risk of lung cancer to a greater extent in smokers [adjusted odds ratio (OR), 0.31; 95% confidence interval (CI), 0.10-0.98] than nonsmokers (OR, 0.70; 95% CI, 0.45-1.11). The inverse association was stronger among subjects with homozygous deletion of GSTM1 and/or GSTT1. Among nonsmokers with GSTM1-null genotype, higher intake of ITCs significantly reduced the risk of lung cancer (OR, 0.54; 95% CI, 0.30-0.95), an effect not seen among those with detectable GSTM1 (OR, 1.07; 95% CI, 0.50-2.29). Our results, in a Chinese female population, are consistent with the hypothesis that ITC is inversely related to the risk of lung cancer, and we show that among nonsmokers this effect may be primarily confined to GST-null individuals. Conjugation and elimination of ITCs is enhanced in GST-non-null relative to -null individuals, such that the GST metabolic genotype modifies the protective effect of ITCs on lung cancer development.

Population-based cancer survival in Singapore, 1968 to 1992: an overview

The Singapore Cancer Registry has provided comprehensive population-based incidence data since 1968. This paper describes the population-based survival analysis of the registry data. All invasive primary cancers diagnosed from January 1, 1968 to December 31, 1992 were passively followed up until December 31, 1997. Only 5.8% were lost to follow-up. Cumulative and observed survival rates were calculated using Hakulinen's method. Overall 5-year relative survival rates have increased dramatically over the 25-year period in both genders. Significant increases are seen with nasopharynx, stomach and colo-rectum cancers, non-Hodgkin's lymphoma, leukemias and cancers of the testis, cervix, ovaries and breast. When compared with the Surveillance, Epidemiology and End Results (SEER) rates in the United States, the 5-year relative survival rates in Singapore are generally lower. However, the rate of change between the two countries is fairly similar. On the average, the rates are 10 to 15 years behind the SEER rates and 5 to 10 years behind Finland, Switzerland and Japan, but they are close to the UK rates. The age-standardized 5-year survival rate for Singapore is higher for most sites compared with other developing countries like Qidong (China), Madras (India), Bombay (India) and Chiang Mai (Thailand). The 25-year trend in cancer survival in Singapore showed two extreme groups: those showing no change and those showing significant improvements. Reducing the incidence of cancers belonging to the first group remains the only viable mode of cancer control. For cancers in the second group, improvement in survival is due to a combination of successful early detection measures and effective treatment services in Singapore.

Do urinary estrogen metabolites reflect the differences in breast cancer risk between Singapore Chinese and United States African-American and white women?

Breast cancer risk is substantially lower in Singapore than in women from the United STATES: Part of the risk discrepancy is probably explained by differences in the production of endogenous estrogens, but differences in the pathway by which estrogen is metabolized may also play a role. We undertook a study to determine whether the ratio of urinary 2-hydroxyestrone (2OHE(1)):16alpha-hydroxyestrone (16alpha-OHE(1)) was higher in Singapore Chinese than in a group of United States (predominantly African-American) women living in Los ANGELES: We also wanted to determine whether any difference in estrogen metabolite ratio between these two groups of women was greater than that in estrone (E(1)), estradiol (E(2)) and estriol (E(3)). The participants in this study were randomly selected healthy, non-estrogen using women participating in the Singapore Chinese Health Study (n = 67) or the Hawaii/Los Angeles Multiethnic Cohort Study (n = 58). After adjusting for age and age at menopause, mean urinary 2-OHE(1) was only 23% (P = 0.03) higher in Singapore Chinese than in United States women, and there were no statistically significant differences in 16alpha-OHE(1) levels or in the ratio of 2-OHE(1):16alpha-OHE(1) between the two groups. The adjusted mean 2-OHE(1):16alpha-OHE(1) ratio was 1.63 in Singapore Chinese and 1.48 in United States women (P = 0.41). In contrast, the adjusted mean values of E1, E2, and E3 were 162% (P < 0.0001), 152% (P < 0.0001), and 92% (P = 0.0009) higher, respectively, in United States women than in Singapore Chinese women. Our study suggests that urinary E1, E2, and E3 reflect the differences in breast cancer risk between Singapore Chinese and United States women to a stronger degree than the estrogen metabolites 2OHE(1) and 16alpha-OHE(1) or the ratio of 2OHE(1):16alpha-OHE(1.)

Cytochrome P4501A2 (CYP1A2) activity and lung cancer risk: a preliminary study among Chinese women in Singapore

There is increasing evidence for the role of heterocyclic and other arylamines in carcinogenesis, including lung carcinogenesis. Chinese women have a high rate of lung cancer despite a low smoking prevalence, and studies in this population may provide useful information on risk factors other than smoking. Hepatic CYP1A2 and NAT2 are involved in the metabolism of carcinogenic arylamines, and NAT2 also catalyzes the detoxification pathway for these compounds. In this study, we examined the effect of CYP1A2 activity using a urinary caffeine metabolic ratio assay for 54 Chinese women with newly diagnosed lung cancer (including 28 adenocarcinomas) and 174 hospital controls. Among them, NAT2 genotype was available for 47 cases and 98 controls. There was no effect of CYP1A2 activity on overall risk of lung cancer in the study population [odds ratio (OR) 0.8, 95% confidence interval (CI) 0.4-1.6, adjusted for age at diagnosis, smoking and cruciferous vegetable intake]. For adenocarcinomas, the OR was 1.5, 95% CI 0.6-3.4. After further adjustment for NAT2 acetylator genotype, the OR for adenocarcinoma was 1.8 (95% CI 0.7-4.8). When the combined NAT2/CYP1A2 status was examined, women with slow NAT2 and rapid CYP1A2 activity were at highest risk (adjusted OR 6.9, 95% CI 1.3-37.6) relative to women with rapid NAT2 and slow CYP1A2 activity, for lung adenocarcinoma. While larger studies are needed to confirm or refute these results, they are consistent with a role for heterocyclic arylamines in lung carcinogenesis in this primarily non-smoking population.

Attitudes as barriers in breast screening: a prospective study among Singapore women

Health care systems do not exist in isolation, but rather, as part of the larger social and cultural mosaic. In particular, perceived attitudes are major obstacles in health promotion exercises. This problem is especially true for non-white populations where little is known about the prevailing social and cultural perceptions towards western biomedical prescriptions. To further our understanding of Asian women's acceptance of mammograms, three attitudinal indexes are conceptualised, constructed and validated. Data from a prospective survey showed the significance of fatalistic attitudes, perceived barriers and perceived efficacy of early detection in predicting women's acceptance of a free mammogram at the National Breast Screening Project. In addition, findings reinforced the importance of social support from the family in the promotion of breast screening among Asian women.

Correlation between acetylation phenotype and genotype in Chinese women

OBJECTIVE

The acetylation polymorphism is a common inherited variation in human drug and carcinogen metabolism. Because N-acetyltransferase (NAT2) is important for the detoxification and/or bioactivation of drugs and carcinogens, this polymorphism has important implications in therapeutics and cancer susceptibility. A high correlation between acetylation phenotype and genotype has been demonstrated in several studies. However, no such data exist for Chinese females. The aim of the present study was to compare acetylation phenotype with NAT2 genotype in a population of primarily non-smoking Chinese females.

METHODS

In the present study, the correlation between N-acetyltransferase activity and NAT2 genotype was evaluated in 103 unrelated Chinese female controls derived from a hospital-based case-control study of lung cancer in Singapore. Acetylation phenotype and genotype were respectively determined using caffeine and an allele-specific polymerase chain reaction (PCR).

RESULTS

The proportions of rapid and slow phenotypes were 78% and 22%, respectively, while the distribution of rapid (heterozygotes and homozygotes combined) and slow acetylator genotypes was 76% and 24%, respectively. The distribution of the various NAT2 genotypes did not differ significantly (chi2 = 1.45, P > 0.05) from that predicted by the Hardy-Weinberg Law. All slow acetylators were accurately predicted (100%), whereas 2 of 80 rapid acetylators were erroneously predicted as slow (2.5%). The overall prediction rate of the PCR-based test for the acetylation phenotype was at 98.1% in our Chinese population.

CONCLUSION

Our results suggest that genotyping with PCR may well become the preferred method for the determination of acetylation polymorphism in epidemiological studies in this Asian population.

Fumes from meat cooking and lung cancer risk in Chinese women

Chinese women are recognized to have a high incidence of lung cancer despite a low smoking prevalence. Several studies have implicated domestic exposure to cooking fumes as a possible risk factor, although the exact carcinogens have yet to be identified. Heterocyclic amines are known carcinogens, which have been identified in cooked meat, and also in fumes generated during frying or grilling of meats. We conducted a case-control study of 303 Chinese women with pathologically confirmed, primary carcinomas of the lung and 765 controls to examine the association between exposure to meat cooking and lung cancer risk. Data on demographic background, smoking status, and domestic cooking exposure, including stir-frying of meat, were obtained by in-person interview while in hospital. The response rates among eligible cases and controls were 95.0 and 96.9%, respectively. The proportion of smokers (current or ex-smokers) among cases and controls was 41.7 and 13.1%, respectively. Adenocarcinomas comprised 31.5% of cancers among smokers and 71.6% among nonsmokers. When cases were compared with controls, the odds ratio (OR) for lung cancer (all subtypes) among ex-smokers was 4.3 [95% confidence interval (CI) 2.7-6.8] and that among current smokers was 5.0 (95% CI, 3.4-7.3). Among smokers, women who reported that they stir-fried daily in the past had a significantly increased risk of lung cancer (adjusted OR, 2.0; 95% CI, 1.0-3.8) and among these women, risk was enhanced for those who stir-fried meat daily (OR, 2.7; 95% CI, 1.3-5.5). Women who stir-fried daily but cooked meat less often than daily did not show an elevated risk (OR, 1.0. 95% CI, 0.5-2.4). Risk was further increased among women stir-frying meat daily who reported that their kitchen was filled with oily fumes during cooking (OR, 3.7; 95% CI, 1.8-7.5). These cooking practices on their own did not increase risk among nonsmokers in our study population. Our results suggest that inhalation of carcinogens, such as heterocyclic amines generated during frying of meat, may increase the risk of lung cancer among smokers. Further studies in different settings are warranted to examine this possibility, which may also help to explain the higher risk observed among women smokers compared with men.

Effects of social support, regular physician and health-related attitudes on cervical cancer screening in an Asian population

OBJECTIVE

Out primary objective was to examine sociodemographic and attitudinal factors that affect uptake of the Pap smear in a multi-ethnic Asian population.

METHODS

We conducted a prevalence survey among women aged 50-64 years living in Singapore and ascertained by means of an in-person questionnaire interview their Pap screening history, demographic characteristics, informal social support and attitudes towards early detection.

RESULTS

We found that, after adjusting for demographic variables known to be predictors of Pap screening, women who reported ever having a Pap smear were more likely to have close friends with whom they could discuss health (adjusted odds ratio (OR) 2.1, 95% confidence intervals (CI) 1.2-3.6), and have a regular physician (adjusted OR 2.3 (1.3-4.1)). Based on responses to four indices measuring health attitudes, they were significantly less likely to express a fatalistic viewpoint towards health and illness (adjusted OR for highest vs. lowest tertile 0.3 (95% CI 0.1-0.7)), and more likely to believe that early detection could improve the outcome (adjusted OR 3.3 (95% CI 1.4-7.8)). The nature of the test itself was a significant barrier to having a Pap smear, but only among women with fewer years of education.

CONCLUSIONS

Our results suggest that, within this Asian population, a multi-pronged approach is required to reach unscreened women. The role of physicians and close friends should be emphasized, and health messages should be formulated to address specific, relevant attitudinal barriers to Pap screening.

Survival of colorectal cancer patients in Singapore by anatomic subsite: a population-based study

INTRODUCTION

Studies of the prognostic value of anatomic subsite in colorectal cancer survival have yielded conflicting results. Two explanations for possible differences in survival patterns between proximal and distal lesions in the colorectum are biological difference between subsites and the presence of more early-stage lesions in distal than in proximal large bowel.

MATERIALS AND METHODS

A total of 435 cases with proximal lesions and an equal number with distal lesions diagnosed between 1990 and 1992 were randomly selected from the Singapore Cancer Registry. Information on vital status at 31 December 1996 were obtained by computerised matching with data from the National Registry of Births and Deaths.

RESULTS

Persons with proximal cancers in our study population did not present at a later stage than persons with distal cancer, local lesions (Dukes' Stage A + B) being 45.5% and 45.1%, respectively. Our analysis showed no significant differences in survival between subsites on a stage-for-stage basis. The 5-year survival rates were 42% and 44% for proximal and distal lesions, respectively (median survival times 3.98 and 4.27 years). Stage at diagnosis was the strongest predictor of survival. Among proximal lesions, 5-year survival rates were 57%, 36% and 12% for local, regional and metastatic lesions, respectively. The corresponding figures for the distal group were 65%, 37% and 10%. Age at diagnosis had a significant influence on survival.

CONCLUSIONS

Our results, based on population-based figures on survival of colorectal cancer patients where the impact of screening has not been large, do not support an independent influence of anatomic subsite in predicting survival of colorectal cancer.

Applications of new technology in molecular epidemiology and their relevance to occupational medicine

Technological advances in molecular biology over the past 2 decades have offered more complex techniques that can be used to study the role of specific exogenous agents and host variables that cause ill health. Increasingly, studies in human populations use this new technology, combined with epidemiological methods, to shed light on the understanding of the biological processes associated with development of disease. This approach has many potential applications in occupational and environmental medicine (OEM), and some aspects of the work in this growing field are reviewed. An understanding of biochemistry and genetics at the molecular level, specific knowledge on metabolism and mechanisms of action, and epidemiology have become increasingly important for the OEM practitioner. This is necessary to consider the major question of validation and relevance of these molecular biomarkers. As end users, OEM practitioners should also consider the impact of these advances on their practices. For example, the availability of genetic tests to identify susceptible workers raises issues of ethics, individual privacy, right to work, and the relevance of such tests. Several studies have presented data on the association of environmental measurements and various biomarkers for internal and biologically effective dose, genetic polymorphisms, and early response markers. Given the limitations of individual molecular biomarkers in assessing risk to health, and the multifactorial nature of environmental disease, it is likely that such an approach will increase our understanding of the complex issue of mechanisms of disease and further refine the process of risk assessment.

NAT2 slow acetylator genotype is associated with increased risk of lung cancer among non-smoking Chinese women in Singapore

Among non-smokers, the factors resulting in lung carcinogenesis are poorly understood. We conducted a hospital-based case-control analysis of 294 Chinese women, of whom 217 were non-smokers, to evaluate the role of polymorphic N-acetyltransferase (NAT2) as a susceptibility factor for the disease. The proportion of slow acetylator genotypes among non-smoking cases (n = 92) and controls (n = 125) was 38.0 and 24.0%, respectively [odds ratio (OR) 2.0, 95% confidence interval (CI) 1.1-3.7]. No effect of NAT2 genotype was seen among smokers. Among non-smokers, the effect was marked for adenocarcinomas (OR 2.1, 95% CI 1.1-4.0). As NAT2 activity is known to modify risk of arylamine-induced carcinogenesis, our results suggest that exposure to arylamines in the environment may play a role in risk of lung cancer among non-smokers.

Patterns of consultation and treatment for heartburn: findings from a Singaporean community survey

BACKGROUND

The prevalence of reflux-type symptoms among community individuals in Singapore is low.

AIM

To describe the healthcare-seeking behaviour of those subjects with heartburn.

METHODS

A cross-sectional survey, using a reliable and valid questionnaire, was carried out on a race-stratified random sample of residents, aged 21-95 years, in a Singaporean town; 93% responded (n = 696).

RESULTS

The ethnic-adjusted prevalence of heartburn for the past 1-year was 4.6%. Sixteen (30%) of the 53 heartburn sufferers had sought consultation for their symptoms. They were more likely to have severe heartburn (P<0.001), and to have complained of nocturnal awakening due to heartburn (P<0.05) than those who did not present to medical attention. Ethnic origin did not influence the consultation pattern. Only 18 (34%) of the 53 heartburn sufferers received pharmacological therapy for their symptoms. The most commonly used medication was antacid. Medication use was associated with symptom severity (P<0.05), but not ethnicity.

CONCLUSIONS

Heartburn is uncommon in the general population of Singapore. Few heartburn sufferers seek medical attention, and most do not receive medications for symptomatic control. The decision to seek medical advice and/or to medicate was generally linked to symptom severity, but not to ethnicity.

A cross-sectional survey of physical activity among middle aged women in Singapore

OBJECTIVES

To assess the extent to which middle-aged women in Singapore engage in physical activity of a level which would result in long-term health benefits, and to determine the factors associated with this.

METHODS

We conducted a cross-sectional survey of women aged between 35 and 60 years residing in Marine Terrace. A standardised questionnaire incorporating a modified Seven-Day Recall Questionnaire was used to record the level and type of physical activity engaged in over the past week. Demographic information and factors promoting or discouraging sports and exercise were also elicited. The total energy expenditure for household, occupational and sports activities of moderate intensity and above was calculated using metabolic equivalents (METs) in kcal/kg/week.

RESULTS

Of the 341 respondents, 50.7% reported engaging in at least moderate activity for 30 minutes or more every day during the past week, thus fulfilling the WHO recommendations on physical activity. Housework contributed significantly to the energy expenditure on these activities among our target population. After adjusting for age, body mass index and educational level, we found that housewives without domestic help were most likely to fulfill the WHO recommendations. Housewives or working women with domestic help were the two groups at highest risk of low physical activity. A lack of time was the reason most commonly cited for not engaging in sports or exercise.

CONCLUSION

Studies assessing physical activity in relation to disease risk among women should include domestic work in addition to the traditional leisure-time activities. There is a scope for further efforts to improve the level of activity in this population, which could be facilitated by the support of health professionals, employers and family members.

Colorectal carcinoma among ethnic Chinese in Singapore: trends in incidence rate by anatomic subsite from 1968 to 1992

BACKGROUND

Recent epidemiologic studies have suggested that the anatomic distribution of colorectal carcinoma may have undergone a distal to proximal shift over several decades, which has been attributed variously to environmental and genetic factors as well as preventive intervention.

METHODS

Trends in subsite distribution and the incidence rate of colorectal carcinoma among Chinese in Singapore between 1968 and 1992 were explored using data from the Singapore Cancer Registry (n = 10,489). Age-standardized incidence rates were computed and compared further using age-period-cohort models by subsite and gender.

RESULTS

The proportion of lesions in the distal colon was found to have increased from 23.2% to 24.4% whereas that for the proximal colon and rectum were fairly consistent over the past 25 years. Our results also showed that age-standardized rates have doubled in proximal lesions (2-3% annually) and more than doubled in distal lesions (3-4% annually) whereas rates in rectal carcinoma have shown a slight increase or stability over time. The patterns of change in all subsite tumors could be attributed to a significant birth cohort effect.

CONCLUSIONS

The results of the current study suggest that incidence rates have increased rapidly with no distal to proximal shift observed among ethnic Chinese in Singapore over the past 25 years. The pattern of change differs from findings reported in high incidence countries such as the U. S. and parts of Europe, suggesting that the preventive intervention and early diagnostic capabilities that may have played an important role in these countries have had less effect in Asia. The rapid overall increase in the incidence rate of colon carcinoma supports the role of dietary and other environmental factors as possible risk factors.

A randomized trial of the use of print material and personal contact to improve mammography uptake among screening non-attenders in Singapore

The Singapore Breast Screening Project was a nationwide study inviting a random sample of women between the ages of 50 and 64 years for mammography at one of two hospital-based screening centres over two years. The current study was undertaken to determine if (1) mailed health educational material alone, or (2) the same material delivered during a home visit made to the subject and her family would increase the uptake among Singapore women who had not responded to two previous invitations for mammographic screening as part of the Project. This randomized trial employed a standard second reminder letter (R), the same letter packaged with health education material designed for the project (RP) and the addition of a home visit to make contact with the woman and her family (RV). The outcome measure of interest was the proportion of women in each group subsequently attending for screening. The study population comprised 1500 non-attenders whose names appeared consecutively in the database of the larger screening centre in this Project. These were randomized into three groups of 500 each. In total, they broadly resembled the national population in ethnic composition (72.3% Chinese, 17.8% Malays, 9.0% Indians and 0.8% Others). By the end of the project, 7.0% of women in group R and 7.6% in group RP responded to the invitation. In group RV, 428 homes were visited at least once and contact was made with the subject and her family member in 306 (71.5%) cases. Subsequently, 13.3% of the women visited attended for screening. The rate ratio for attendance in group RP compared with group R was 1.09 (95% CI 0.70 to 1.70) and for group RV compared with R, 1.90 (1.27 to 2.84). When analyzed by groups originally assigned to, women in group RV remained significantly more likely to attend than those in groups R or RP. The marginal cost of a home visit, based on this study, was $25.04 per additional woman screened. Our results suggest that the response to a second reminder is generally low and that additional print material does not improve screening attendance in this group of initial non-attenders. Personal contact with the family through a home visit appears to increase uptake, and may be helpful particularly among women who have less frequent contact with the health care system.

Prevalence of gastrointestinal symptoms in a multiracial Asian population, with particular reference to reflux-type symptoms

OBJECTIVE

Data on the epidemiology of chronic gastrointestinal symptoms in the East are limited. The aims of this study were to estimate the prevalence of chronic gastrointestinal symptoms in Singapore and to determine whether ethnic differences in the prevalence of these symptoms exist.

METHODS

A cross-sectional survey, using a reliable and valid questionnaire, was carried out in a race-stratified random sample of residents aged 21-95 yr (mean+/-SD, 40+/-1 yr) in a Singaporean town; 93% responded (n=696).

RESULTS

The ethnic-adjusted prevalence of chronic abdominal pain, frequent dyspepsia, irritable bowel syndrome, chronic constipation, chronic diarrhea, and frequent reflux were 5.7% (95% confidence interval [CI], 3.3-8.1), 7.9% (95% CI, 5.0-10.8), 2.3% (95% CI, 0.8-3.9), 3.9% (95% CI, 1.9-5.9), 4.5% (95% CI, 2.3-6.7), and 1.6% (95% CI, 0.6-2.6), respectively. There were no ethnic differences in the prevalence of any of these symptom categories except for reflux-type symptoms, which were more common among Indians (7.5%; 95% CI, 4.4-11.7) than Chinese (0.8%; 95% CI, 0.1-3.0) or Malays (3.0%; 95% CI, 1.26.1).

CONCLUSION

The prevalence of all types of chronic gastrointestinal symptoms in the general population of Singapore was low compared with those in the West. Chronic gastrointestinal symptoms were equally prevalent in the three major ethnic groups except for reflux-type symptoms, which were more common among Indians than Chinese or Malays.

Prevalence of gastrointestinal symptoms in a multiracial Asian population, with particular reference to reflux-type symptoms

OBJECTIVE

Data on the epidemiology of chronic gastrointestinal symptoms in the East are limited. The aims of this study were to estimate the prevalence of chronic gastrointestinal symptoms in Singapore and to determine whether ethnic differences in the prevalence of these symptoms exist.

METHODS

A cross-sectional survey, using a reliable and valid questionnaire, was carried out in a race-stratified random sample of residents aged 21-95 yr (mean+/-SD, 40+/-1 yr) in a Singaporean town; 93% responded (n=696).

RESULTS

The ethnic-adjusted prevalence of chronic abdominal pain, frequent dyspepsia, irritable bowel syndrome, chronic constipation, chronic diarrhea, and frequent reflux were 5.7% (95% confidence interval [CI], 3.3-8.1), 7.9% (95% CI, 5.0-10.8), 2.3% (95% CI, 0.8-3.9), 3.9% (95% CI, 1.9-5.9), 4.5% (95% CI, 2.3-6.7), and 1.6% (95% CI, 0.6-2.6), respectively. There were no ethnic differences in the prevalence of any of these symptom categories except for reflux-type symptoms, which were more common among Indians (7.5%; 95% CI, 4.4-11.7) than Chinese (0.8%; 95% CI, 0.1-3.0) or Malays (3.0%; 95% CI, 1.26.1).

CONCLUSION

The prevalence of all types of chronic gastrointestinal symptoms in the general population of Singapore was low compared with those in the West. Chronic gastrointestinal symptoms were equally prevalent in the three major ethnic groups except for reflux-type symptoms, which were more common among Indians than Chinese or Malays.

Cross cultural adaptation and validation of the Chinese Health Assessment Questionnaire for use in rheumatoid arthritis

OBJECTIVE

The Health Assessment Questionnaire - Disability Index (HAQ), used as a disability and outcome measurement in rheumatoid arthritis (RA), has been validated in several languages, but not in Chinese. Our aim was to validate the Chinese version of HAQ (Chinese-HAQ) to suit the needs of Chinese speaking patients with RA in an Asian setting.

METHODS

The original HAQ was modified in the context of Chinese culture and translated into Chinese by 2 translators aware of the objective of the questionnaire. The Chinese HAQ was self-administered by 42 patients with RA during their routine followup visit and one week later.

RESULTS

The test-retest reliability assessed using Spearman's correlation coefficient was 0.84. Between dimensions measured in the HAQ, the highest test-retest reliability was observed for walking (Spearman correlation coefficient rs=0.80) and the lowest was for eating (rs=0.54). The internal consistency of the scale using Cronbach's alpha was high at 0.86. In terms of criterion validity, the Chinese-HAQ score was found to correlate well with American College of Rheumatology functional status (rs=0.501, p=0.01). The Chinese-HAQ scores also correlated well with markers of disease activity such as patient's perception of pain measured on a visual analog scale (rs=0.55, p < 0.001), grip strength in mm Hg (rs=-0.55. p < 0.001 ), and physician's assessment of disease activity (rs=0.59, p < 0.001).

CONCLUSION

The Chinese HAQ is a reliable and valid instrument for studies measuring disability of patients with RA in Singapore.

Urinary total isothiocyanate (ITC) in a population-based sample of middle-aged and older Chinese in Singapore: relationship with dietary total ITC and glutathione S-transferase M1/T1/P1 genotypes

Isothiocyanates (ITCs), degradation products of glucosinolates (which occur naturally in a variety of cruciferous vegetables), have been shown to exhibit chemopreventive activity. These compounds are metabolized in vivo to form the corresponding dithiocarbamates, which are the major urinary metabolites of ITCs, by a pathway involving the glutathione S-transferase (GST) class of enzymes. Using a newly developed assay that measures total ITC (primarily ITC conjugates) in urine, we examined the relationships between cruciferous vegetable intake (obtained from a food frequency/portion size questionnaire administered in person); dietary total ITC level; GSTM1, GSTT1, and GSTP1 genotypes; and levels of total ITC in spot urine samples collected from 246 Singapore Chinese (111 men and 135 women), ages 45-74 years, who are participants of the Singapore Cohort Study on diet and cancer. Consumption level of cruciferous vegetables was high in study subjects (mean consumption = 345 times per year, mean daily intake = 40.6 g), which was >3 times the comparable level of intake in the United States. Mean daily intake of total ITC among study subjects was 9.1 micromol, and there was a 2.5-fold difference between the 25th and 75th percentile values. Seventy-three % of study subjects tested positive for ITC in urine, and there was a 4-fold difference between the 25th and 75th percentile values among the positive subjects. There was a highly significant positive association between dietary intake and urinary excretion levels of total ITC (two-sided P = 0.0003) that was stronger than the association between overall cruciferous vegetable intake and urinary ITC level, which also was statistically significant (P = 0.0004). There was no difference in urinary ITC levels between GSTM1-null and GSTM1-positive study subjects (P = 0.61) or between subjects with differing GSTP1 genotypes (P = 0.77), but urinary excretion of ITC was significantly higher among GSTT1-positive subjects, relative to GSTT1-null subjects (P = 0.006). The strength of the association between GSTT1 genotype and urinary total ITC level was highly dependent on the level of cruciferous vegetable consumption (or dietary ITC level) in study subjects. Among subjects in the lowest tertile of cruciferous vegetable intake, there was little evidence of an association between GSTT1 genotype and urinary total ITC level (P = 0.67). In contrast, there was a strong and statistically significant association between GSTT1 genotype and urinary total ITC among subjects in the highest tertile of cruciferous vegetable intake (P = 0.02), whereas those in the middle tertile of cruciferous vegetable consumption exhibited an association of intermediate strength (P = 0.04). These results suggest the presence of GSTT1 inducers in cruciferous vegetables.

Prevalence of snoring and sleep breathing-related disorders in Chinese, Malay and Indian adults in Singapore

This study investigated the prevalence of snoring and symptoms of sleep breathing-related disorders in the multi-ethnic population of Singapore (3 million people, comprising 75% Chinese, 15% Malay and 7% Indian). A multistaged, area cluster, disproportionate stratified, random sampling of adults aged 20-74 yrs was used to obtain a sample of 2,298 subjects (65% response), with approximately equal numbers of Chinese, Malay and Indian and in each 10 yr age group. An interviewer-administered field questionnaire was used to record symptoms of snoring and breathing disturbances during sleep witnessed by a room-mate and other personal and health-related data. The weighted point estimate (and 95% confidence interval) of the whole population prevalence of snoring was 6.8% (53-83). There were pronounced ethnic differences among Chinese, 6.2% (4.4-8.1); Malay, 8.1% (6.1-10.2) and Indian, 10.9% (85-13.4). The minimum whole population prevalence by the most restricted symptom criteria for defining sleep breathing-related disorder was 0.43% (0.05-0.8%). Similar marked ethnic differences in rates were observed using various symptom criteria. The ethnic differences in sleep breathing symptoms paralleled the differences in body mass index, neck circumference and hypertension, but statistically significant differences remained after adjustment for sex, age and these known associated factors. Marked ethnic differences in snoring and sleep breathing-related disorders were observed in Chinese, Malays and Indians in Singapore, which were only partly explained by known factors of sex, age and body habitus.

Results of intermediate measures from a population-based, randomized trial of mammographic screening prevalence and detection of breast carcinoma among Asian women: the Singapore Breast Screening Project

BACKGROUND

Although increasing rates of breast carcinoma incidence have been observed in Asian countries, appropriate strategies for detecting early stage breast carcinoma in such communities have been difficult to formulate, particularly because no large population screening trial specifically involving Asian women has been reported. The objective of this study was to evaluate the effectiveness and quality of mammography as a screening technique for Singaporean women, who are predominantly Chinese.

METHODS

In this prospective study, 166,600 women in Singapore ages 50-64 years were randomized to either 2-view mammography without physical examination (67,656) or observation (97,294, controls) over 2 years.

RESULTS

Of these women, 28,231 (41.7%) responded and were screened; they were more likely to be married, have more formal education, be working, be Chinese, and be in a higher socioeconomic group (P < 0.001 for all variables). To assess for response bias that could affect outcome, results were also evaluated for nonrespondents (n = 39,425). The incidence rate of cancers among nonrespondents (1 per 1000 woman-years) was less than the 1.3 in women not invited to have screening (P = 0.03, relative risk [RR], 1.3; 95% confidence interval [CI], 1.0-1.7). However, cancers arising from nonrespondents did not differ significantly in stage distribution when compared with cancers within the control group. For every 1000 women screened, 4.8 cancers were detected. The prevalence ratio (the number of cancers detected per 1000 women at first screening divided by the corresponding incidence rate in controls per year) was 3.6 for screened women and 2.4 for women invited to have screening. The majority of cancers detected through screening were early stage, with 64% as either ductal carcinoma in situ (26%) or Stage I disease (38%) and was significantly more than the corresponding 26% in women not invited to have screening (P < 0.001). When only invasive cancers were considered, screened women still had more early cancers, with 65% having no lymph node involvement, compared with 47% in the group not invited to have screening (P = 0.001; RR, 1.4; 95% CI, 1.2-1.7). Women who were screened had half the risk of having Stage II or later cancers (P < 0.0001; RR, 0.5; 95% CI, 0.4-0.7) when compared with women not invited to have screening. This higher detection rate of early cancers through screening was accomplished with acceptable recall rates of 8% for further mammographic films or physical examination and a biopsy rate of 1.0% (10 per 1000 women screened). The interval cancer rate was 2.1 per 10,000 women screened in the first year of follow-up.

CONCLUSIONS

These positive results of intermediate measures suggest that, in Asian communities, screening mammography could be an important modality for detecting early stage breast carcinoma. However, the low compliance rates suggest that health education efforts must focus on issues related to acceptability if such programs are to succeed.

Lung cancer among Chinese females in Singapore 1968-1992: time trends, dialect group differences and implications for aetiology

BACKGROUND

Chinese females are distinguished internationally as having relatively high lung cancer incidence rates despite a low prevalence of cigarette smoking. In Singapore, this population comprises several dialect groups which have origins in different regions in China, each with its own traditional cultural practices.

METHODS

An analysis of 4029 incident cases of the disease notified to the Singapore Cancer Registry for 1968-1992 was undertaken to provide some insight into important aetiologic factors among these women.

RESULTS

The age-standardized incidence rate of lung cancer rose from 17.3 per 100,000 woman-years in 1968-1972 to 23.0 in 1978-1982 before falling off in more recent years. Age-period-cohort analysis indicated significant period and birth cohort effects, with the risk being highest for women born around 1908. Between the major dialect groups, Cantonese women had a significantly high rate compared with Hokkiens (relative risk [RR] = 2.6, 95% CI: 2.4-2.8). Histologically, there appears to be an increase in the proportion of adenocarcinomas diagnosed over this period (25.8% in 1968-1972 to 51.3% in 1988-1992).

CONCLUSION

Our results suggest that traditional practices which have decreased over the years, and are more prominent among Southern Chinese, may play a part in the aetiology of lung cancer locally.

Population-based mammographic screening in Singapore: what are participants' views?

Mammographic screening for breast cancer has been shown to be an effective tool for reducing mortality from the disease in many studies in the West, if high technical quality and acceptance by the target population are achieved. The objective of the Singapore Breast Screening Project was to determine if the same results could be obtained among local women by inviting a random sample of 69,500 women aged 50 to 64 years for a screening mammogram over two years. To date, the compliance rate among the women invited has been 41.7%. The objective of the present substudy was to determine participants' views on the accessibility and acceptability of organised mammographic screening. Of the three hundred women interviewed, 85% were satisfied with the information given prior to the visit, while 67% needed to change the original appointment given. The majority were satisfied with aspects of the visit such as waiting time, privacy and explanation given during the test. However, 35.1% reported at least moderate discomfort during mammography. A substantial proportion (39.7%) of attenders felt that there was very little hope of cure even if cancer was detected early. When asked the most important reason for attending, most indicated they had taken the opportunity for a free check-up to be assured they were well. Almost all (95.7%) reported a willingness to be screened again, but most would not be willing to pay for a mammogram at the current rates.

Isoflavonoid levels in spot urine are associated with frequency of dietary soy intake in a population-based sample of middle-aged and older Chinese in Singapore

Soy products contain high amounts of isoflavonoids, which have been shown to exhibit possible cancer-protective properties. Chinese populations in Asia, in particular, have a high level of soy intake and a relatively low risk of hormone-dependent cancers. In this study, we assessed the distributions of dietary soy isoflavonoids (daidzein, genistein, and glycitein) and urinary soy isoflavonoids and their metabolites (daidzein, genistein, glycitein, equol, and O-desmethylangolensin) among 147 Singapore Chinese (76 men and 71 women) ages 45-74 years, who are participants of the Singapore Cohort Study on diet and cancer. Urinary values were measured from spot samples collected 10-20 months following recruitment, when usual dietary habits were assessed by a structured food frequency/portion size questionnaire administered in person. Dietary levels of daidzein and genistein were comparable within individuals and about seven times higher than the level of dietary glycitein. All three dietary isoflavonoids showed an approximately 3.5-fold difference between the 25th and 75th percentile values. Similarly, daidzein was the most abundant and glycitein the least abundant of the five isoflavonoid compounds in urine. There was a 4.9-fold difference between the 25th and 75th percentile values for the sum of the five urinary isoflavonoids. Among study subjects, there were statistically significant, dose-dependent associations between frequency of overall soy intake and levels of urinary daidzein (two-sided P = 0.03) and sum of urinary daidzein, genistein, and glycitein (two-sided P = 0.04). In contrast, there were no associations between frequency of overall soy intake and levels of the two daidzein metabolites (equol and O-desmethylangolensin) in urine (two-sided P = 0.85 and 0.34, respectively). We suggest that within the range of exposures experienced by Singapore Chinese, urinary level of daidzein or the sum of daidzein, genistein, and glycitein obtained from a spot sample can serve as a biomarker of current soy consumption in epidemiological studies of diet-disease associations.

Factors determining acceptability of mammography in an Asian population: a study among women in Singapore

Population-based mammographic screening has been shown to be effective in reducing breast cancer mortality in the West. In Singapore, a project carried out to determine the effectiveness of implementing such a program locally invited 28,000 women between the ages of 50 and 64 years for mammography. The current study, which was part of this larger project, was intended to determine factors contributing to the acceptance of mammographic screening among women in Singapore. A questionnaire was administered in-person to 300 attenders and 260 non-attenders. The respondents were compared with respect to basic demographic characteristics, previous preventive behavior, informal social support, and attitudes towards early detection. We found that screening attenders were more likely to be Chinese than Malays (14 percent of the population) or Indians (seven percent), and to be working outside the home (adjusted odds ratio [OR]) = 4.5, 95 percent confidence interval [CI] = 2.6-7.9). A greater proportion of attenders had a history of other screening tests such as the Pap smear (OR = 4.7, CI = 2.6-8.7 for recent smear compared with never having had a smear). They were also more likely to indicate a sense of personal susceptibility to cancer, but did not differ from non-attenders in terms of believing in cancer prevention, or of preferring to be told if they did have cancer. The strongest independent predictor of attendance, however, was encouragement by her spouse or family member. For women in this population to be persuaded effectively to participate in mammographic screening, it would be important to convince family members of the benefits of the test. At the same time, education targeted specifically at women of the appropriate age group should address the issue of the personal relevance of screening for breast cancer.

SLE mortality in an oriental population

We analysed the causes of 67 deaths, over a 4 y period, in our oriental population with systemic lupus erythematosus (SLE). The median disease duration was 48 +/- 60.5 months (range 1-250 months). The mean age at diagnosis and death were 30 and 35.1 y respectively. SLE alone accounted for death in 30 patients (44.8%), infection in 27 (40.3%), pulmonary embolism in 5 (7.5%), malignancy in 4 (5.9%) and rheumatic heart disease in 1 (1.5%). The major organ involvement in those with active disease at death were SLE related thrombocytopenia (n = 23/44, 52.3%), nephritis (n = 21/44), 47.7%), cerebral lupus (n = 16/44, 36.4%), and pulmonary haemorrhage (n = 12/44, 27.3%). As in other series, SLE and infection were the principal causes of death in our population. During this 4 y period, there was no late death due to atherosclerosis.

Non-Hodgkin's lymphoma in an Asian population: 1968-1992 time trends and ethnic differences in Singapore

BACKGROUND

Non-Hodgkin's lymphoma has increased in incidence in many countries, particularly in the West. Advances in diagnostic methods and the understanding of the disease over time pose a challenge to the interpretation of these trends. The aim of this study was to determine if the disease has increased in Singapore, a newly industrialized Asian country, and to examine the possible factors that may account for any observed changes.

METHODS

Data from the population-based Singapore Cancer Registry for the period 1968 to 1992 were reviewed to determine time trends based on sex and ethnic group. The Poisson regression model was fitted to the cross-tabulated data to obtain the adjusted incidence density ratios.

RESULTS

A total of 1988 cases of non-Hodgkin's lymphoma were included in the analysis. There was an overall increase in incidence among both Chinese and Malaysians. However, the rate of increase was greater in females (age-standardized rate from 1.8 per 100,000 in 1968-1972 to 4.5 per 100,000 in 1988-1992) than in males (3.2 per 100,000 to 5.9 per 100,000 in the same time periods). Between ethnic groups, Malay females were at higher overall risk compared with their Chinese counterparts (incidence density ratio 1.32; 95% confidence interval, 1.08-1.61). Although a substantial proportion of patients diagnosed with Hodgkin's disease between 1968 and 1972 were reclassified on review, using present criteria, as having non-Hodgkin's lymphoma, it is unlikely that this, and other recent changes in histologic interpretation, could have accounted for an increase of this magnitude.

CONCLUSIONS

Non-Hodgkin's lymphoma has increased in incidence among the Chinese and Malay populations in Singapore. The pattern of increase differs from that of the common cancer sites, and suggests the need to look for environmental and genetic factors that have not yet been elucidated.

Comparison of upright inspiratory and expiratory chest radiographs for detecting pneumothoraces

OBJECTIVE

Expiratory films are regarded as being superior to inspiratory films for pneumothorax detection, yet this has not been proved. In the current study, we compared inspiratory versus expiratory chest radiographs for pneumothorax detection.

MATERIALS AND METHODS

Eighty-five paired inspiratory and expiratory radiographs with pneumothoraces and 93 pairs without pneumothoraces were randomly arranged and reviewed independently by three radiologists. A score of 1-5 was assigned for each hemithorax (5 = definite pneumothorax, 1 = definitely no pneumothorax). Results were compared for inspiration and expiration using receiver operating characteristic (ROC) analysis.

RESULTS

The average area under the ROC curves for all readers was .973 for inspiration and .972 for expiration (nonsignificant). McNemar's test and an alpha level of .05 also yielded no significant difference in sensitivity and specificity. Four of the 85 cases were scored as definite pneumothorax on inspiration and as definitely not on expiration by all readers, and three of the 85 cases were scored as definite pneumothorax on expiration and as definitely not on inspiration.

CONCLUSION

Inspiratory and expiratory upright films are equally sensitive for pneumothorax detection. Given the limitations of expiratory films, inspiratory films are recommended as the initial examination of choice for pneumothorax detection.

Breast cancer in Singapore: trends in incidence 1968-1992

BACKGROUND

Breast cancer is the most commonly occurring cancer among women in Singapore, a country which has experienced significant changes in lifestyle over the past three decades. The increase in incidence of the disease is a matter of some concern.

METHODS

Data from the population-based Singapore Cancer Registry for 1968-1992 were used to determine time trends, inter-ethnic differences and the contributions of age, period and cohort effects to the incidence of the disease.

RESULTS

Our results revealed an average annual increase of 3.6% over the 25-year period for all women, form 20.2 per 100,000 women in the period 1968-1972 to 38.8 per 100,000 in 1988-1992. There was a statistically significant difference between the three major ethnic groups, the rate of increase being highest in Malays (4.4%) and lowest in Indians (1.4%). The overall increase was attributable to a strong cohort effect that remained significant when adjusted for time period for Chinese women and for all ethnic groups combined. The risk was observed to increase in successive birth cohorts from the 1890s to 1960s.

CONCLUSIONS

Our results suggest that breast cancer incidence rates are likely to continue to increase more sharply in the future as women born after the mid-20th century reach the high-risk age groups. They also suggest the pattern by which important aetiological factors for the disease in our population have exerted their effects, and provide support for the role of demographic and lifestyle changes as possible risk factors.

Biomarkers: a molecular approach to cancer epidemiology

The rapidly evolving field of molecular epidemiology represents a paradigm shift in medical research, illustrating the convergence of basic, clinical and epidemiologic research, as well as the application of laboratory methods to population studies. As a complement and improvement to traditional epidemiologic approaches, the use of biomarkers offers more accurate exposure assessment at an individual level, better understanding of the biological mechanism of carcinogenesis by tracking a continuum of events between exposure and disease, as well as the ability to discern host or genetic factors that may account for variations in cancer susceptibility among individuals or ethnic populations. Further, biomarkers have also proved useful in cancer diagnosis and prognosis. This article attempts to review the latest progress in molecular cancer epidemiology and to summarise the current state of research in Singapore.

Molecular epidemiology: issues in study design and statistical analysis

Traditional analytical epidemiology is directed at identifying the association between risk factors and occurrence of disease by using crude exposure data derived from questionnaires or clinical measures, and taking clinical disease as the end point. With the rapid development in molecular biology and laboratory methods, it is now possible to use biomarkers which are capable of identifying molecular events for epidemiologic research. This improved sensitivity enables us to develop a mechanistic understanding of disease causation: a step closer to the unravelling of the "black box" of traditional epidemiology. Biomarkers may be classified as internal indicators of exposure (biomarkers of exposure), indicators of preclinical adverse effect (biomarkers of effect) or indicators of an intrinsic or acquired susceptibility to disease (biomarkers of susceptibility). Biomarkers provide a better definition of exposure and disease status and consequently they could help to reduce misclassification bias in both exposure and disease, reduce the follow-up time in prospective studies, as well as identify possible interactions between risk factors on disease occurrence. However, a biomarker needs to be validated and its distribution in large populations described before it can be used profitably for aetiologic research. Also, the use of biomarkers in epidemiologic research raises other interesting epidemiological and statistical issues like confounding, effect modification and the analysis of repeated measurements. Molecular epidemiology is a multidisciplinary endeavour which comprises molecular biology, epidemiology and biostatistics. Clearly then, to carry out research in this field profitably, the molecular biologist, epidemiologist and biostatistician must acquire not only expertise in their respective fields, but also an integrated understanding of all three fields. The molecular biologist is not merely a laboratory bench worker; the epidemiologist, a field data-collector and the biostatistician, a number cruncher. They must work together to pry open the "black box" to gain a greater insight into how risk factors operate to initiate disease onset and ultimately to make use of this knowledge base to implement preventive measures.

Beliefs and attitudes as determinants of cervical cancer screening: a community-based study in Singapore

BACKGROUND

The investigation of cervical cancer screening acceptance in relation to health beliefs and attitudes presents a challenge in a multiethnic population such as Singapore's, where the uptake is currently suboptimal in high-risk groups. This study attempts to identify cognitive barriers to screening activity in order to suggest possible directions for cervical cancer prevention efforts.

METHODS

A cross-sectional survey consisting of a household interview of 640 randomly selected women ages 21-65 years was performed. The screening history and future intention to have a Pap smear were elicited, and attitudes toward cancer and the Pap smear as expressed in 14 statements were measured on a five-point scale.

RESULTS

Of the respondents, 73.1% were aware of the Pap smear, and about half (49.7%) had obtained the information from a doctor or nurse. Overall, the belief in personal susceptibility to cancer was low (58.9%) and a substantial proportion (48.7%) of women were of the attitude that cancer could not be prevented. The effect on a future intention to have a smear varied between women who had had and women who had not had a smear. Among the former, perceived barriers such as discomfort and embarrassment had a significant influence, while a belief in personal susceptibility was an important determinant for the latter group.

CONCLUSIONS

The means of increasing the acceptance of the Pap smear, both for the first time and subsequently, are culture-specific and must address the appropriate health beliefs and attitudes. In Singapore, such efforts should include not only influencing awareness and perceptions through public education but also reducing barriers by creating an appropriate environment for the delivery of this important health service.

The role of scintigraphy in the evaluation of fever of unknown origin

Nuclear medicine imaging techniques are an important adjunct to other currently used modalities in the evaluation of patients with fever of unknown origin. Bone scanning performed with technetium-labeled phosphonate agents may identify osteomyelitis when plain radiography fails and may disclose sites of joint inflammation or unsuspected osseous tumor metastasis. Indium-labeled autologous leukocytes localize at sites of inflammation in the same manner as unlabeled leukocytes. Gallium citrate accumulates in areas of inflammation and in some tumors, most notably lymphomas. In most cases, scintigraphy is best used to determine the location of a lesion rather than to specifically identify the pathologic process.

From colony to city state: changes in health needs in Singapore from 1950 to 1990

The disease patterns and health needs of Singaporeans have altered dramatically over the last half-century as a result of both economic progress and socio-demographic change. This is reflected by improvements in the universal indices of health status such as the infant mortality rate and life expectancy at birth. At the same time, chronic degenerative diseases such as cancer and heart disease have replaced infectious diseases as the major causes of death, as is the pattern in industrialized countries throughout the world. The challenge for public health in Singapore today is to find cost-effective means to control these diseases, and in this regard, the country has embarked on a strategy of disease prevention and health promotion for the next decade, aimed at reducing the levels of major lifestyle-related risk factors by providing a supportive environment for behavioural change.

Prevalence and determinants of cervical cancer screening: a community-based study in Singapore

A cross-sectional survey of 568 married women aged 21-65 years in the Pasir Panjang Constituency was conducted to determine the prevalence of cervical cancer screening in the community and the factors affecting acceptance of this screening test. Results show that 309 (54.4%) of the respondents had ever had a Pap smear. The women who reported having had a smear were more likely to be below 45 years of age (prevalence ratio 1.47, 95% confidence interval 1.15 to 1.88), Chinese and of a higher socioeconomic status (1.68, 1.33 to 2.12). They were also more likely to have married at a later age (1.68, 1.21 to 2.31) than women who had not had a smear. Age and socioeconomic status remained independent predictors on multivariate analysis. The findings suggest that an important task of public health practitioners is to increase the uptake of screening among older and socially disadvantaged women who are known to be at the highest risk of cervical cancer. In addition, strategies to encourage younger women to continue regular attendance at screening clinics beyond their childbearing years will be important for the future.

Adult onset polymyositis/dermatomyositis: clinical and laboratory features and treatment response in 75 patients

OBJECTIVES

To determine possible similarities and differences in clinical and laboratory features and treatment response between patients in Singapore with polymyositis (PM) and dermatomyositis (DM) and reported series.

METHODS

Case records of adult patients (16 years old and above) referred to the 3 main electromyographic (EMG) laboratories in Singapore between 1 June 1986 and 31 May 1991 were reviewed if the referring diagnosis was myositis or myopathy for investigation. A computer search for adult patients with a diagnosis of PM/DM (ICD codes 710.3, 710.4, 517.8) who attended the main rheumatology and neurology centre during this period was also carried out. The criteria for PM/DM proposed by Bohan and Peter was adopted.

RESULTS

The incidence of PM/DM was 7.7 cases per million population per year. There were 35 PM and 40 DM cases with a median age at diagnosis of 50.7 years (SD: 16.7) and significantly more females in the PM group (p < 0.05). At presentation, 86.7% had proximal myopathy, 34.7% had arthralgia/arthritis and 18.7% had cutaneous vasculitis. The creatine kinase level was elevated in 89.3% of patients and positive EMG and muscle biopsy in 79.4% and 76.4% respectively. Systemic lupus erythematosus was the commonest associated connective tissue disease. The percentage of patients with malignancy was higher in DM compared with PM (p < 0.01) and they were significantly older (mean age 61.8 years) (p < 0.001). Patients who achieved remission were significantly younger (mean age 46.4 years, p < 0.05). The overall mortality rate was 26.7% with infection and malignancy as the main causes of death.

CONCLUSION

The results of the study suggest ethnicity does not influence the expression of PM/DM in view of the considerable similarities in frequency and clinical expression of disease in the population studied compared with series from other countries.

Cervical cancer: trends in incidence and mortality in Singapore 1968 to 1987

Analysis of data collected by the population-based Singapore Cancer Registry reveals that the age-standardised incidence of cervical cancer has decreased from 18.2 per 100,000 females in 1968-72 to 16.2 per 100,000 in 1983-87, and its ranking among the most common female cancers has fallen from second to fourth place behind cancers of the breast, colon/rectum and lung. Mortality from the disease has also shown a corresponding fall from 7.3 per 100,000 to 5.5 per 100,000 women over the same period. Cervical cancer incidence rates are in general highest among Indian women, intermediate in Chinese and lowest in Malays. Age-specific incidence curves over time show a marked fall in rates in women over 50 years of age, whereas younger women (35-44 years old) show a small increase. A similar increase in rates has been observed in various other countries. Internationally, Singapore's incidence rate falls between the highs of South America and parts of Asia, and the lower rates of North America and Europe. The decrease in rates is comparable with the overall global trend, but falls short of that achieved by countries with systematic cytological screening programmes.

Awareness and acceptance of hepatitis B vaccination in Clementi, Singapore

Hepatitis B Virus infection, a public health problem in Singapore, can be effectively controlled by vaccination. This paper reports on a study conducted in 1988/89 to ascertain the awareness and uptake rate of Hepatitis B vaccination. A list of children born between November 1986 and May 1987 in the catchmen zone of the Clementi Maternal and Child Health (MCH) Clinic was obtained. Out of a total of 257 children, 226 (87.9%) responded to our study in May 1988 which was part of a larger community health survey carried out by a group of medical students. The vaccination uptake rate was 23%. The awareness of the parents on Hepatitis B virus infection and vaccination was assessed using a standardised questionnaire. About two-thirds were aware of the main modes of Hepatitis B transmission, 46.5% were aware of the long-term consequences of Hepatitis B infection and 6.6% thought that the vaccine was not safe from serious side effects. A follow-up survey of the respondents was carried out in August 1989. The Hepatitis B vaccination uptake had increased to 48.3%. The immunisation status showed a correlation with the ethnic group, father's occupation and awareness score of respondents. The more than two-fold increase in uptake rate can be attributed to a reduction in the cost of Hepatitis B vaccination and a vigorous nation-wide education programme during the preceding year.