Occupational risk factors for nasopharyngeal cancer among female textile workers in Shanghai, China

AIMS

To investigate whether occupational exposure to dusts and chemicals in the Chinese textile industry are associated with risk of nasopharyngeal cancer.

METHODS

Sixty seven nasopharyngeal carcinoma (NPC) cases identified during 1989-98 and a random sample (n = 3188) of women were included in a case cohort study nested in a cohort of 267,400 women textile workers in Shanghai, China. A complete occupational history of work in the textile industry was obtained for each woman. A job exposure matrix developed by experienced industrial hygienists was used to assess exposures to specific dusts and chemicals.

RESULTS

Risk of NPC is associated with cumulative exposure to cotton dust. The hazard ratio for women cumulatively exposed to >143.4 mg/m3 x years of cotton dust was 3.6 (95% CI 1.8 to 7.2) compared with unexposed women. Trends of increasing risk were also found with increasing duration of exposure to acids and caustics (p = 0.05), and with years worked in dyeing processes (p = 0.06). Women who worked at least 10 years in dyeing processes had a 3.6-fold excess risk of NPC (95% CI 1.0 to 12.1).

CONCLUSIONS

Occupational exposure to cotton dust, acids, and caustics, and work in dyeing and printing jobs in the textile industry may have increased risk of NPC in this cohort.

Occupational exposures and risks of liver cancer among Shanghai female textile workers--a case-cohort study

BACKGROUND

Liver cancer is the fifth most frequent malignancy worldwide. Viral hepatitis B and C, alcohol, and aflatoxin are the major established risk factors. Little is known about the aetiological contributions of occupational exposures, as previous occupational epidemiological studies of liver cancer suggest few agent-specific associations. We investigated associations of occupational exposures to dusts and chemicals in a cohort of female textile workers.

METHODS

Cancer incidence was determined among 267,400 female textile workers in Shanghai, China, who had been enrolled in an intervention trial of breast self-exam efficacy during 1989-98. Subjects were interviewed at baseline regarding basic demographics, smoking habits, alcohol consumption, and contraceptive practices. A case-cohort study of 360 liver cancer cases and 3,186 age-stratified randomly chosen subcohort subjects was conducted within this cohort. Exposures to workplace dusts and chemicals were reconstructed from complete work history data, historical exposure monitoring data for selected agents, and a specially designed job-exposure matrix for the textile industry. Relative risks and dose-response trends were estimated by Cox proportional hazards modelling, adapted for the case-cohort design. Latency analyses with different lag years were also applied.

RESULTS

2,095,904 person-years were contributed by this female cohort. The results of the case-cohort analysis revealed a protective effect of cotton fibre exposure years [adjusted hazards ratio (HR) = 0.64; 95% confidence interval (95% CI) 0.44-0.92] or endotoxin exposure (adjusted HR = 0.60; 95% CI 0.41-0.88) for the fourth quartile with significant trends for 20 year exposure lags.

CONCLUSIONS

This study suggests that chronic exposure to endotoxin or some other component of cotton dust exposure may have reduced liver cancer risk in this population.

Dietary and other risk factors in women having fibrocystic breast conditions with and without concurrent breast cancer: a nested case-control study in Shanghai, China

Risk of breast cancer is increased in women with proliferative benign breast conditions. Most of these conditions, however, do not progress to breast cancer. The purpose of our study was to identify factors possibly associated with this progression. Women with proliferative fibrocystic breast conditions alone (214), and women with proliferative fibrocystic breast conditions and concurrent breast cancer (130), were compared to each other, and each of these groups of women were also compared to 1,070 controls; and 176 women with non-proliferative benign breast conditions alone, and 155 also with breast cancer, were similarly compared. All study subjects were selected from a cohort of women enrolled in a trial of breast self-examination in Shanghai. Women were interviewed to ascertain information on suspected risk factors for breast cancer and dietary habits. Conditional logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI). Increased risks of both proliferative fibrocystic breast conditions alone, and with breast cancer, were associated with low parity, a prior benign breast lump and breast cancer in a first-degree relative. Decreasing trends in the risk of both conditions with increasing intake of fruits and vegetables were observed. No factors were significantly associated with risk of breast cancer relative to risk of proliferative changes. Similar, but in some instances weaker, associations were observed for non-proliferative fibrocystic conditions with and without breast cancer. The possible risk or protective factors that were observed in our study most likely alter the risk of breast cancer at an early stage in the carcinogenic process, and probably do not alter risk of progression from proliferative fibrocystic breast conditions to breast cancer.

[Randomized trial of breast self-examination in 266,064 women in Shanghai]

OBJECTIVE

A randomized trial of breast self-examination (BSE) program was carried out to evaluate whether the intensive BSE can reduce the death number of women from breast cancer.

METHODS

A total of 266,064 women (age of 30 to 64 years) associated with 519 textile factories in Shanghai had been randomly assigned to a BSE instruction group (132,979 women) or a control group (133,085 women) since 1989. Initial instruction in BSE group included demonstration of proper palpation techniques. It was followed by 2 reinforcement sessions during the subsequent 4 years including video shows, BSE instruction sessions and BSE practice under medical supervision. These activities were continued for 5 years. Attendance at all events was recorded. The cohort was followed through July 2000 for development of breast diseases, and the breast cancer cases were followed up through 2001 for vital status. The data analysis methods used included Kaplan-Meier plots, Log-rank test and Cox modeling.

RESULTS

Among women under instruction, 864 breast cancers were detected and 133 breast cancer deaths occurred, and 896 breast cancers were detected and 130 deaths recorded in the control group. The tumor size (P = 0.07), TNM stage (P = 0.39) and cumulative breast cancer mortality rate (P = 0.72) were not significantly different between the 2 groups. However, more and smaller fibroadenomas were detected in the instruction group than in the control group (P < 0.01).

CONCLUSION

Intensive instruction in BSE can not reduce mortality rate of breast cancer, but more and smaller benign breast lumps can be detected.

A case-control study of risk factors for fibrocystic breast conditions: Shanghai Nutrition and Breast Disease Study, China, 1995-2000

This study was conducted to identify reproductive and dietary factors associated with benign proliferative mammary epithelial cell changes. Subjects were women enrolled in a randomized trial of breast self-examination in Shanghai, China. Women who developed fibrocystic breast conditions classified as nonproliferative (175 women), proliferative (181 women), or proliferative with atypia (33 women) between 1995 and 2000 and 1,070 unaffected trial participants were administered general risk factor and food frequency questionnaires. Conditional logistic regression was used to estimate adjusted odds ratios and 95% confidence intervals. High parity and consumption of fresh fruits and vegetables were more strongly associated with a reduced risk of proliferative and atypical lesions than with nonproliferative conditions. For the fourth quartile of consumption versus the first, odds ratios for lesions diagnosed as nonproliferative, proliferative, and proliferative with atypia were 0.4 (95% confidence interval (CI): 0.2, 0.7), 0.2 (95% CI: 0.1, 0.4), and 0.1 (95% CI: 0.03, 0.5), respectively, for fruit intake and 0.6 (95% CI: 0.3, 1.1), 0.4 (95% CI: 0.2, 0.7), and 0.1 (95% CI: 0.1, 0.9), respectively, for vegetable intake. Reduced but nonsignificant risks in relation to soy products were observed for proliferative and atypical lesions. No single nutrient or botanical family was appreciably more strongly associated with proliferative conditions than with nonproliferative conditions, after results were controlled for total fruit and vegetable consumption. A diet rich in fruits and vegetables may reduce cellular proliferation in the mammary epithelium; this is one mechanism by which such a diet could reduce risk of breast cancer.

Contraceptive methods and induced abortions and their association with the risk of colon cancer in Shanghai, China

267400 female textile workers in Shanghai, who were administered a questionnaire at enrollment into a randomised trial of breast self-examination between October 1989 and October 1991, were followed up until the middle of 2000. Based on the 655 women who developed colon cancer, rate ratios (RRs) were estimated and trends in risk assessed using Cox Proportional Hazards Models. Risk was increased in women who used oral contraceptives for over 3 years (RR=1.56, 95% Confidence Interval (CI) 1.01-2.40). A possible increase in risk was also observed in women who received progestational injections during pregnancy (RR=1.24, 95% CI 0.95-1.62), but not in relation to the use of injectable contraceptives. A possible reduction in risk was associated with tubal ligation (RR=0.86, 95% CI 0.71-1.03) and ever having had an induced abortion (RR=0.84, 95% CI 0.71-1.00). No trends in risk were observed in relation to the duration of hormonal contraceptive use or the number of induced abortions. Additional studies of the possible roles contraceptives may play in the aetiology of colon cancer in women at low risk of this disease are warranted.

BRCA1 and BRCA2 Mutations in Women from Shanghai China

Little is known about the frequency of germ-line mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 among Asian populations. We investigated the distribution of BRCA1 and BRCA2 germ-line mutations and polymorphisms in a cohort of women from Shanghai, China. Study subjects totaled 1306, and included 645 women with breast cancer, 342 women with benign breast disease, and 319 unaffected controls, born between 1924 and 1958, selected from women enrolled in a randomized trial of Breast Self-Examination in Shanghai, China. Women were selected without regard to family history of breast or ovarian cancer. All of the coding regions and exon-intron boundaries were screened. Data were analyzed with respect to age at diagnosis, and family history of breast and ovarian cancer. The prevalence of known disease-associated mutations in women with breast cancer was 1.1% each, for BRCA1 and BRCA2. Among breast cancer cases with a family history of breast or ovarian cancer, 8.1% and 2.7% carried likely BRCA1 and BRCA2 disease-associated mutations, respectively. Overall, these results suggest that inherited susceptibility to breast cancer due to germ-line BRCA1/2 mutations among women with a family history of breast cancer is comparable between women from Shanghai and Caucasian women of Western European descent. Most alterations observed appear unique to the Chinese population, suggesting a resource that will be useful for assessing risk among both Chinese women and United States women of Chinese descent.

Cancer among women textile workers in Shanghai, China: overall incidence patterns, 1989-1998

BACKGROUND

Cancer incidence in women textile workers has not been adequately studied. The aim of this study was to examine site-specific cancer incidence patterns in a cohort of 267,400 women textile workers in Shanghai, China.

METHODS

Women employed by the Shanghai Textile Industry Bureau (STIB) were followed for cancer incidence from 1989 to 1998. Age-adjusted standardized incidence ratios (SIRs) and 95% confidence intervals (CI) were computed based on Shanghai Cancer Registry (SCR) rates.

RESULTS

There was a decrease in cancer incidence for the cohort compared with urban Shanghai women (SIR = 0.91, 95% CI = 0.89-0.93). There were small increased risks of other endocrine tumors (SIR = 1.31, 95% CI = 1.02-1.65). There were decreased risks for esophageal (SIR = 0.54, 95% CI = 0.44-0.66), stomach (SIR = 0.79, 95% CI = 0.73-0.85), rectal (SIR = 0.88, 95% CI = 0.78-0.98), lung (SIR = 0.80, 95% CI = 0.74-0.86), cervical (SIR = 0.37, 95% CI = 0.28-0.50), ovarian (SIR = 0.85, 95% CI = 0.75-0.96), and bladder cancers (SIR = 0.63, 95% CI = 0.46-0.85).

CONCLUSIONS

Women employed in the textile industry had a lower than expected cancer experience compared with urban Shanghai women. Further research on this cohort will examine associations between site-specific cancers and occupational exposures to dusts and chemicals.

Risk factors for progression of squamous cell cervical carcinoma in-situ to invasive cervical cancer: results of a multinational study

OBJECTIVE

Human papillomaviruses (HPVs) are probably necessary causes of cervical carcinoma, but few infected women develop invasive cervical cancer, suggesting a role for cofactors. The purpose of this study was to identify cofactors associated with progression of carcinoma in-situ to invasion.

METHODS

Data from in-person interviews of women included in a multinational, hospital-based case-control study of in-situ and invasive squamous cell cervical carcinoma were analyzed. In-situ cases and controls were compared to identify risk factors for carcinoma in-situ, and invasive and in-situ cases were compared to identify risk factors for progression to invasive disease.

RESULTS

Risk of invasion was decreased in women with a history of cytologic screening, and in relation to other variables that likely represent enhanced opportunities for screening or clinical evaluation of symptomatic disease. No other risk or protective factors for progression were convincingly demonstrated. Risk of progression was not associated with multiple incidences of promiscuous sexual behavior, or use of steroid contraceptives, although there was a possible association with high parity.

CONCLUSIONS

Possible cofactors that have been considered in this study alter the carcinogenicity of an HPV infection primarily prior to the development of cervical carcinoma in-situ. Women with a history of this condition need not avoid use of steroid contraceptives.

Breast cancer in relation to induced abortions in a cohort of Chinese women

The possible influence of induced abortion on breast cancer risk was assessed in a cohort of 267 040 women enrolled in a randomised trial of breast self-examination in Shanghai, China. Based on answers to a baseline questionnaire, subsequent breast cancer risk was not significantly associated with ever having an induced abortion. After adjustment for potential confounders, the relative risk estimate was 1.06 (95% C.I.: 0.91, 1.25), and there was no trend in risk with number of abortions. Analysis of data from more detailed interviews of 652 cases and 694 controls from the cohort yielded similar results. There was also no overall increase in risk in women with induced abortion after first birth. Few women had undergone an abortion after 13 weeks gestation or before their first child. Although increases in risk were observed in such women, they were not statistically significant and could have been due to recall bias. Abortions as they have been performed in China are not an important cause of breast cancer.

Randomized trial of breast self-examination in Shanghai: final results

BACKGROUND

Among women who practice breast self-examination (BSE), breast cancers may be detected when they are at an earlier stage and are smaller than in women who do not practice BSE. However, the efficacy of breast self-examination for decreasing breast cancer mortality is unproven. This study was conducted to determine whether an intensive program of BSE instruction will reduce the number of women dying of breast cancer.

METHODS

From October 1989 through October 1991, 266,064 women associated with 519 factories in Shanghai were randomly assigned to a BSE instruction group (132,979 women) or a control group (133,085 women). Initial instruction in BSE was followed by reinforcement sessions 1 and 3 years later, by BSE practice under medical supervision at least every 6 months for 5 years, and by ongoing reminders to practice BSE monthly. The women were followed through December 2000 for mortality from breast cancer. Cumulative risk ratios of dying from breast cancer were estimated using Cox proportional hazards models. All statistical tests were two-sided.

RESULTS

There were 135 (0.10%) breast cancer deaths in the instruction group and 131 (0.10%) in the control group. The cumulative breast cancer mortality rates through 10 to 11 years of follow-up were similar (cumulative risk ratio for women in the instruction group relative to that in the control group = 1.04, 95% confidence interval = 0.82 to 1.33; P =.72). However, more benign breast lesions were diagnosed in the instruction group than in the control group.

CONCLUSIONS

Intensive instruction in BSE did not reduce mortality from breast cancer. Programs to encourage BSE in the absence of mammography would be unlikely to reduce mortality from breast cancer. Women who choose to practice BSE should be informed that its efficacy is unproven and that it may increase their chances of having a benign breast biopsy.

Dietary risk factors for invasive and in-situ cervical carcinomas in Bangkok, Thailand

OBJECTIVE

Although human papillomavirus (HPV) may be a necessary cause of cervical cancer, most women with HPV infections do not develop this disease. This study was conducted to evaluate the possible effects of specific dietary factors on cervical carcinogenesis.

METHODS

Fifty hospitalized in-situ cases and 125 controls were identified from family planning or gynecologic clinics associated with Siriraj hospital in Bangkok, Thailand, and 134 hospitalized invasive cases and 384 hospitalized controls from the public wards of Siriraj Hospital were administered a food-frequency questionnaire and tested for HPV DNA in exfoliated cervical cells. Odds ratios in relation to intake of foods high in vitamin C, folate, vitamin E, vitamin A, beta-carotene, retinol, and cruciferous vegetables were estimated using logistic regression in case-control comparisons and in case-case comparisons adjusted for HPV status.

RESULTS

High intake of foods rich in vitamin A, and particularly high-retinol foods, were associated with a reduced risk of in-situ disease and less strongly also with a reduced risk of invasive as compared to in-situ disease. No association was found between intake of cruciferous vegetables, foods high in vitamin C, folate, vitamin E, and beta-carotene and risk of either in-situ or invasive cervical cancer.

CONCLUSIONS

Increasing intake of foods rich in total vitamin A, and particularly high-retinol foods, may reduce risk of in-situ cervical cancer, and at the highest level of intake may inhibit progression to invasion. If others confirm these results they suggest means of reducing the risk of cervical cancer that are amenable to public health action.

Risk factors for fibroadenoma in a cohort of female textile workers in Shanghai, China

Risk factors for fibroadenoma were investigated in a cohort of 265,402 female textile workers in Shanghai, China, who were interviewed at enrollment into a randomized trial of breast self-examination between October 1989 and October 1991 and followed until July 2000. Based on 1,507 women who developed fibroadenoma, relative risks and trends in risk were estimated using Cox regression. The risk of fibroadenoma was highest in women under 35 years of age, and it decreased with age after 35 and dropped markedly at the time of menopause. The risk decreased with increasing number of livebirths and with duration of oral contraceptive use. The risk increased with number of prior benign breast lesions and with decreasing age at the first benign lesion. The risk of a diagnosis of fibroadenoma was elevated in women who received instruction in breast self-examination. The development and persistence of fibroadenomas are dependent on the presence of ovarian hormones, and full-term pregnancies and exposure to exogenous estrogen-progesterone combinations before menopause may reduce risk by enhancing differentiation or reducing estrogen-induced proliferation in the mammary epithelium. The practice of breast self-examination detects some fibroadenomas that would otherwise not be detected.

Risk of subsequent breast cancer in relation to characteristics of screening mammograms from women less than 50 years of age

This investigation was conducted to assess the predictive value of calcifications and densities in mammograms from women <50 years of age for subsequent diagnosis of breast cancer. In a population-based study, prior screening mammograms taken before age 50 in 547 women with breast cancer and 472 controls were reviewed by a single radiologist. The relative risk (RR) of subsequent breast cancer increased with the percentage of the area of the mammogram that was mammographically dense [RR in succeeding quartiles of density = 1.0, 1.7 (1.1-2.6), 3.3 (2.2-5.0), and 4.0 (2.7-6.0)]; in relation to Wolfe parenchymal pattern class P2 [RR = 3.1 (2.2-4.3)] or DY [RR = 5.6 (3.2-10.0)]; and in relation to calcifications of class 1 (pleomorphic of any distribution) or class 2 (various morphological types that are regional, grouped, clustered, segmental, or linear in distribution) [RR = 3.0 (1.4-7.1), and 1.8 (1.2-2.6), respectively]. Women with radiographically dense mammograms and class 1 or 2 calcifications were at >10- and approximately 6-fold greater risk, respectively, than women with breasts of low density and no calcifications. Densities and parenchymal patterns were most strongly associated with breast cancer being diagnosed in the next 3 years. Class 1 and 2 calcifications were most strongly predictive of an increased risk in 3-6 years. Class 1 calcifications were strongly predictive of the breast in which the subsequent cancer occurred. Women <50 years of age with class 1 or 2 calcifications or mammographically dense breasts, or both, should receive high priority for further evaluation and regular breast cancer screening.

Polyamine depletion induces rapid NF-kappa B activation in IEC-6 cells

The proliferation of the rat intestinal mucosal IEC-6 cell line requires polyamines, whose synthesis is catalyzed by the enzyme ornithine decarboxylase (ODC). ODC inhibition leads to polyamine depletion, as well as inhibition of both cell proliferation and apoptosis by regulating gene expression. The NF-kappa B transcription factor regulates genes involved in apoptotic, immune, and inflammatory responses. In the present study we tested the hypothesis that NF-kappa B is activated following ODC inhibition. We found that the inhibition of ODC by alpha-difluoromethylornithine (DFMO) resulted in a approximately 50% decrease in intracellular putrescine levels within 1 h. NF-kappa B is activated by DFMO through the degradation of the inhibitory protein I kappa B alpha that sequesters NF-kappa B in the cytoplasm. The DFMO-induced NF-kappa B complexes contain the p65 and p50 members of the Rel protein family. DFMO-induced NF-kappa B activation was accompanied by the translocation of p65 from the cytoplasm into the nucleus. DFMO selectively inhibited a gene reporter construct dependent on the kappa B site present in the HLA-B7 gene. In contrast, DFMO had no effect on a gene reporter construct dependent on the kappa B site present in the interleukin-8 gene. Thus, we report that ODC inhibition activates the NF-kappa B transcription factor, which may mediate the altered physiological state of intestinal cells that occurs following polyamine depletion.

Airway management in the obese child

Airway management in severely obese children requires familiarity with the equipment and techniques used for establishing a patent airway. Normal anatomic landmarks are obscured in these patients, making assessment a challenge. Therapy should be individualized, and because the airway is marginal in many of these patients, small insults, such as respiratory tract infection or loss of muscle tone during sleep, can result in a perilous airway. Pediatric airway charts should be maintained and reviewed frequently in emergency departments and clinics caring for these patients. Currently, the body of literature devoted to airway management in obese children is small. Inconsistencies in parameters make comparison of studies difficult. Continued, consistent reporting of airway-management issues in these patients is needed.

Focal adhesion kinase signaling is decreased in polyamine-depleted IEC-6 cells

Polyamines are essential to the migration of epithelial cells in the intestinal mucosa. Cells depleted of polyamines do not attach as rapidly to the extracellular matrix and do not form the actin stress fibers essential for migration. Because both attachment and stress fiber formation depend on integrin signaling and the formation of focal adhesions, we examined these and related processes in polyamine-depleted IEC-6 cells. There was general decreased tyrosine phosphorylation of focal adhesion kinase (FAK), and, specifically, decreased phosphorylation of Tyr-925, the paxillin binding site. In control cells, FAK phosphorylation was rapid after attachment to the extracellular matrix, while attached cells depleted of polyamines had significantly delayed phosphorylation. FAK activity was also significantly inhibited in polyamine-depleted cells as was the phosphorylation of paxillin. Polyamine-depleted cells failed to spread normally after attachment, and immunocytochemistry showed little colocalization of FAK and actin compared with controls. Focal adhesion complex formation was greatly reduced in the absence of polyamines. These data suggest that defective integrin signaling may, at least in part, account for the decreased rates of attachment, actin stress fiber formation, spreading, and migration observed in polyamine-depleted cells.

Polyamine depletion arrests growth of IEC-6 and Caco-2 cells by different mechanisms

The polyamines spermidine and spermine and their precursor, putrescine, are required for the growth and proliferation of eukaryotic cells. This study compares and contrasts growth arrest caused by polyamine depletion in the untransformed IEC-6 cell line with that in the p53-mutated colon cancer Caco-2 cell line. Cells were grown in the presence or absence of alpha-difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase, the first rate-limiting enzyme in the synthesis of polyamines. Depletion of polyamines inhibited the growth of both cell lines equally and over the same time frame. However, whereas IEC-6 cells were arrested in the G(1) phase of the cell cycle, there was no accumulation of Caco-2 cells in any particular phase. In IEC-6 cells, growth arrest was accompanied by elevated levels of p53 and p21(Waf1/Cip1) (p21). There were no changes in p53 levels in Caco-2 cells. Levels of p21 increased in Caco-2 cells on day 2 without any effect on cell cycle progression. The amount of cyclin-dependent kinase (Cdk)2 protein was unchanged by polyamine depletion in both cell lines. However, the activity of Cdk2 was significantly inhibited by DFMO in IEC-6 cells. These data suggest that in the untransformed IEC-6 cells the regulation of Cdk2 activity and progression through the cell cycle are p53- and p21 dependent. Growth arrest in the p53-mutated Caco-2 line after polyamine depletion occurs by a different, yet unknown, mechanism.

Human papillomaviruses and cervical cancer in Bangkok. III. The role of husbands and commercial sex workers

Between September 1991 and September 1993, husbands of women with and without cervical neoplasia and commercial sex workers in one brothel and one massage parlor in Bangkok, Thailand, were interviewed; serologic tests for sexually transmitted infections were performed; and cervical and penile scrapings were tested for human papillomavirus (HPV) DNA. The risks of cervical carcinoma in monogamous women and of oncogenic HPV in their husbands were associated with the men's having unprotected intercourse with prostitutes. The prevalence of oncogenic HPV was higher in commercial sex workers than in women attending gynecologic and family planning clinics. Oncogenic HPV prevalence declined with age in human immunodeficiency virus (HIV)-negative, but not in healthy HIV-positive, commercial sex workers and was weakly associated with hepatitis B antigenemia, suggesting that persistence of HPV infection is due to subtle changes in immunity. Associations of HPV with recent pregnancy and oral contraceptive use suggest that hormonal factors may increase the risk of cervical neoplasia by enhancing persistence of HPV infection. The prevalence of high-grade squamous intraepithelial lesions was strongly related to oncogenic HPV types and weakly to HIV infection only in their presence. Commercial sex workers in Bangkok are reservoirs of oncogenic HPV, and cervical cancer in monogamous Thai women develops in part as a result of transmission of these viruses to them by their husbands from prostitutes.

Human papillomaviruses and cervical cancer in Bangkok. II. Risk factors for in situ and invasive squamous cell cervical carcinomas

To identify risk factors for progression of intraepithelial cervical lesions, 190 women with invasive cervical cancer were compared with 75 women with in situ disease diagnosed in Bangkok, Thailand, between September 1991 and September 1993. Polymerase chain reaction-based assays for type-specific human papillomavirus (HPV) DNA in cervical scrapings revealed oncogenic types in 79% of invasive and 57% of intraepithelial tumors. Types 16 and 18, but not types 31/33/35/39, were more common in invasive than intraepithelial tumors, and untyped HPV DNA was found more commonly in the in situ lesions, suggesting that in situ disease is four times more likely to become invasive if due to type 16 or 18 than to other causes, and that tumors with only untyped HPV are not at increased risk of progression. After controlling for HPV type, the risk of developing invasive diseases, compared with the risk of developing intraepithelial lesions, was not related to any of a large number of sexual and hormonal factors considered or to smoking, suggesting that any cofactors these variables represent act before the development of in situ carcinoma. Two indices of socioeconomic status were associated with a reduced risk of only invasive disease, suggesting the existence of unknown protective factors that operate after intraepithelial lesions develop.

Human papillomaviruses and cervical cancer in Bangkok. I. Risk factors for invasive cervical carcinomas with human papillomavirus types 16 and 18 DNA

Personal interviews, tests for antibodies to herpes simplex virus type 2, Treponema pallidum, and hepatitis B, tests for hepatitis B surface antigen (HBsAg), and polymerase chain reaction-based assays for human papillomavirus (HPV) DNA in cervical scrapings were obtained from 190 women with squamous cell and 42 women with adenomatous cervical carcinoma and from 291 hospitalized controls diagnosed in Bangkok, Thailand, between September 1991 and September 1993. Risk was strongly associated with oncogenic HPV types, with types 16 and 18 predominating in squamous and adenomatous lesions, respectively. The 126 cases with HPV-16 and the 42 cases with HPV-18 were compared with 250 controls with no evidence of any HPV. The risk of both viral tumor types increased with decreasing age at first intercourse in this predominantly monogamous population, which may be explained by more visits to prostitutes by the husbands of cases with early than late age at first intercourse. HPV-16 tumors were weakly associated with HBsAg carrier state and smoking. The risk of tumors of both viral types increased with parity and use of oral contraceptives but not with injectable progestogens. Factors that may predispose to persistent, oncogenic HPV-16 or -18 infection may include estrogens or progestins in the presence of estrogens, immunosuppression, and smoking, but other factors related to low socioeconomic status are also involved.