Co-factors related to the causal relationship between human papillomavirus and invasive cervical cancer in Honduras

Effects of short-term ambient air pollution exposure on HPV infections: A five-year hospital-based study

Human papillomavirus (HPV) infections are common sexually-transmitted diseases among reproductive-aged women with increasing concern. Until now, there are no prior study about the association between HPV infections and ambient air pollution. This study aimed to explore the relationship between short-term exposure to ambient pollutants and daily outpatient visits for HPV infections in China. Data of daily outpatient visits for HPV infections were obtained from January 1, 2014 to December 31, 2018 (1826 days). Over-dispersed Poisson generalized additive models were applied by adjusting weather conditions and day of the week. We identified a total of 39,746 cases for HPV infections. A 10 μg/m³ increase of PM₁₀, PM_2.5, SO₂, and NO₂ or a 0.1 mg/m³ rise of CO in concurrent day (lag 0) concentrations was related to an elevation of 0.822% (95% Cl: 0.282%, 1.36%), 1.05% (95% Cl: 0.280%, 1.81%), 5.72% (95% Cl: 1.79%, 9.65%), 5.02% (95% Cl: 3.45%, 6.60%), and 2.40% (95% Cl: 1.43%, 3.37%) in daily outpatient-visits for HPV infections, respectively. The association was more significant in those women aged 41 or over. As for 10 μg/m³ increase of O₃, a -1.33% (95% Cl: -2.13%, -0.530%) change was observed on the lag 03 and such effects appeared to be more obvious in the aged 18-40 group. Our results provided the first evidence that short-term exposure to ambient pollutants was related to, which may be indirectly, the increased risk of HPV infections while O₃ may act as a "protective" factor.

Solid fuel use for heating and risks of breast and cervical cancer mortality in China

BACKGROUND

Carcinogens released from indoor burning of solid fuels are believed to enter the bloodstream and to be metabolized in breast and cervical tissues. Little evidence exists about the relationship of solid fuel use from heating with breast and cervical cancer.

OBJECTIVES

To examine the association of solid heating fuel use with breast and cervical cancer mortality.

METHODS

This study included female participants aged 30-79 years who were enrolled in the China Kadoorie Biobank during 2004-2008 from 10 diverse regions across China. During a 10.2-year median follow-up, 177 breast cancer deaths and 113 cervical cancer deaths were documented. Multivariable Cox regression models yielded adjusted hazard ratios (HRs) for the associations of self-reported long-term heating fuel exposure with two cancer deaths. Stratified analyses were used to assess effect modification.

RESULTS

We included 236,116 participants for breast cancer analyses and 228,795 for cervical cancer analyses. Compared with non-solid fuel use, the fully adjusted HRs of cervical cancer deaths were 1.75 (0.91-3.38) for wood use, 2.23 (1.09-4.59) for mixed fuel (coal and wood) use. No evident relationship was observed for breast cancer deaths. Cervical cancer risk increased with the duration of solid fuel use (P for trend = 0.041). Elevated cervical cancer risk was observed in post-menopausal women (HR 2.01, 1.01-4.03), not in pre-menopausal women (HR 0.77, 0.56-2.31) (P for heterogeneity = 0.004); and in those aged ≥50 years (HR 2.56, 1.17-5.86), not in those aged < 50 years (HR 0.69, 0.26-1.84) (P < 0.001).

CONCLUSION

Indoor solid fuel combustion for heating may be associated with a higher risk for cervical cancer death, but not for breast cancer. The strength of the association increased with the duration of exposure and was modified by age and menopause status.

The contribution of Latin American research to HPV epidemiology and natural history knowledge

Our aim was to review the major contributions of studies conducted in different Latin American (LA) countries to the field of human papillomavirus (HPV) epidemiology, natural history, risk of disease, and prevention strategies, mainly in the uterine cervix. Although cytological screening is established in several countries in LA, incidence and mortality rates from cervical cancer (CC) are still extremely high. Finally, data from large cohort studies conducted in LA countries provided seminal data to propose primary and secondary prevention modalities: the HPV vaccine has been introduced in the national immunization programs of several LA countries and multiple screening experiences using HPV testing are under evaluation in the region.

Exposure to biomass smoke as a risk factor for oesophageal and gastric cancer in low-income populations: A systematic review

Background

Upper gastrointestinal cancers contribute significantly to cancer-related morbidity and mortality in sub-Saharan Africa, but they continue to receive limited attention. The high incidence in young adults remains unexplained, and the risk factors have not been fully described.

Methods

A literature search was conducted using the electronic database PubMed. Beginning from January 1980 to February 2016, all articles evaluating biomass smoke exposure with oesophageal and gastric cancer were reviewed.

Results

Over 70% of the African population relies on biomass fuel, meaning most Africans are exposed to biomass smoke throughout their lives. Cigarette smoke is an established risk factor for upper gastrointestinal cancers, and some of its carcinogenic constituents are also present in biomass smoke. We found eight case-control studies reporting associations between exposure to biomass smoke and oesophageal cancer, and two linking biomass smoke to gastric cancer. All of these papers reported significant positive associations between exposure and cancer risk. Further research is needed in order to fully define the constituents of biomass smoke, which could each have varying specific and synergistic or independent contributions to the development of upper gastrointestinal cancers

Conclusions

Exposure to biomass smoke is an environmental factor influencing the development of upper gastrointestinal cancers, especially in low-resource settings.

Co-carcinogenesis: Human Papillomaviruses, Coal Tar Derivatives, and Squamous Cell Cervical Cancer

Cervical cancer (CC) is the fourth most common cancers among women worldwide. Human papillomaviruses (HPVs) play a major role in the etiology of CC, with several lines of epidemiologic and experimental evidence supporting a role for non-viral (co-carcinogens) and host genetic factors in controlling the risk for progression to neoplasia among HPV-infected individuals. The role of co-carcinogens in the development of CC is significant in the developing world where poor sanitation and other socio-economic conditions increase the infectious cancer burden. Here, we discuss how exposure to environmental factors such as coal tar derivatives from cigarette smoking, tar-based sanitary products, and inhaled smoke from biomass-burning stoves, could activate host pathways involved in development of HPV-associated squamous cell cancers in resource-limited settings. Understanding interactions between these pathways with certain oncogenic HPV genotypes may guide implementation of strategies for control and treatment of HPV-associated cancers that develop in populations at high risk of exposure to various co-carcinogens.

Socio-Demographic, Reproductive and Clinical Profile of Women Diagnosed with Advanced Cervical Cancer in a Tertiary Care Institute of Delhi

INTRODUCTION

Cervical cancer is one of the leading cancers among Indian women with estimated 123,000 new cases and 67,477 deaths in 2012. Cervical cancer is a multi-etiological disease. Factors such as low socioeconomic status, tobacco use, sexual and reproductive factors, HIV and other sexually transmitted diseases and long-term oral contraceptive use have been suggested as determinants. Assessment of socio-demographic profile and reproductive history gives a better picture of the determinants of cervical carcinoma in low-resource settings.

METHODS

This hospital-based cross-sectional study was undertaken at a tertiary healthcare institute at New Delhi, India. Sixty-seven newly diagnosed women with advanced cervical cancer (stage 2B-4B), who were undertaking radio- and/or chemotherapy, were included to assess their socio-demographic, reproductive and clinical profile.

RESULTS

The mean age of women at the time of detection of cervical cancer was 52.28 ± 11.29 years (range 30-75 years). More than 60 % of patients were illiterate and belonged to middle socioeconomic status. Thirty-nine percentage of the study subjects had their first sexual experience before 15 years of age. Nearly 54 % women had 5 or more pregnancies. Nearly 73 % of women had all deliveries at home. Majority (69 %) of women had symptoms suggestive of reproductive tract infection. Among them, unusual discharge from vagina (73.13 %) followed by bleeding after menopause (55.10 %) and pain in abdomen (44.77 %) were the most common presenting complaints. Pallor was present in nearly two-third (63.93 %) study subjects. More than half (56.72 %) study subjects had moderate anemia, and 7.46 % had severe anemia before treatment. Mean hemoglobin level of the study subjects was 10.35 ± 1.72 gm% before treatment and 9.69 ± 1.29 gm% after treatment. This difference was statistically significant. Around 97 % of the study subjects had squamous cell carcinoma of the cervix. Majority (53.73 %) of the study subjects were in stage 3B of cervical cancer. Combination of radiotherapy and chemotherapy was the most common (77.67 %) modality of treatment.

CONCLUSIONS AND RECOMMENDATIONS

Illiteracy, low socioeconomic status, early sexual debut, high fertility, home delivery, reproductive tract infections, use of insanitary clothes during menstruation and anemia were observed in majority of women with advanced cancer cervix. Presence of these factors indicates possible risk of cervical cancer and should be kept in mind when women seek health services. Early diagnosis through high risk or opportunistic screening and timely management of cervical cancer needs to be ensured for better outcomes.

Socio-demographic and reproductive determinants of cervical neoplasia in seven sub-Sahara African countries

BACKGROUND

Since most human papilloma virus (HPV) infections regress without any intervention, HPV is a necessary but may not be a solely sufficient cause of cervical intraepithelial neoplasia (CIN) and cervical cancer. Hence, the influence of cofactors on progression from cervical HPV infection to high-grade CIN and invasive cervical cancer has been a subject of intensive research.

OBJECTIVE

We assessed the effect of socio-demographic and sexual reproductive factors on the prevalence of invasive cervical cancer and CIN diagnosed in cross-sectional cervical cancer screening projects carried out in seven sites of different sub-Saharan countries.

METHODS

Between January 2000 and August 2007, healthy women aged 25-59 who participated in the screening projects were interviewed for socio-demographic, reproductive, and behavioral characteristics, investigated for disease confirmation with colposcopy, and had biopsies directed from colposcopically abnormal areas by trained local physicians. Odds ratios (ORs) and their 95% confidence intervals (CIs) from logistic regression analyses were used to assess the effect of women characteristics on CIN 1, CIN 2-3, CIN 3, and invasive cancer outcome measures.

RESULTS

Among 47,361 women screened and investigated for disease confirmation, CIN 1 was diagnosed in 1,069 (2.3%), CIN 2 in 517 (1.1%), CIN 3 in 175 (0.5%), and invasive cancer in 485 (1.0%). The site-specific prevalence of CIN 2-3 lesions ranged from 0.3 to 5.1% and from 0.2 to 1.9% for invasive cancers. Risk factors for CIN 2-3 were being widowed or separated versus currently married (OR 1.3, 95% CI 1.0-1.7 a); and having had at least four pregnancies versus zero or one pregnancy (OR at least 1.4-fold, 95% CI 1.1-1.8). Risk factors for invasive cancer were being widowed or separated versus currently married (OR 2.0, 95% CI 1.3-3.1); and having had at least three pregnancies versus zero or one pregnancy (OR at least 3.0-fold, 95% CI 2.1-4.2). Additionally, cervical cancer risk increased with increasing age, age at menarche, and age at marriage, while the risk decreased with increasing level of education and in those with some form of employment compared to housewives.

CONCLUSION

The exposure of the exocervix and/or the increased levels of estrogen and progesterone for more prolonged periods during pregnancy in multiparous women and the vulnerability of widowed/separated women in society might result in increased risk of cervical neoplasia more so among women exposed to HPV infection. High parity probably explains the persistently high rates of cervical cancer in sub-Saharan Africa.

Household air pollution and cancers other than lung: a meta-analysis

Household air pollution (HAP) from solid fuel combustion contributes to 2.6% of the global burden of disease. HAP emissions are an established lung carcinogen; however, associations with other cancer sites have not been fully explored. We conducted a meta-analysis of 18 case-control studies. Using fixed-effects models, utilizing the adjusted odds ratios (OR) and 95% confidence intervals (95% CI) from each study, we evaluated the association between HAP and cervical neoplasia (663 cases and 1747 controls) and upper aero-digestive tract cancers (6022 cases and 15 325 controls). We found that HAP was associated with cervical neoplasia (OR = 6.46; 95% CI = 3.12-13.36; 4 studies); oral (OR = 2.44; 95% CI = 1.87-3.19; 4 studies; 1000 cases/3450 controls); nasopharyngeal (OR = 1.80; 95% CI = 1.42-2.29; 6 studies; 2231 cases/2160 controls); pharyngeal (OR = 3.56; 95% CI = 2.22-5.70; 4 studies; 1036 cases/3746 controls); and laryngeal (OR = 2.35; 95% CI = 1.72- 3.21; 5 studies; 1416 cases/4514 controls) cancers. The elevated risk for esophageal cancer (OR = 1.92; 95% CI = 0.82-4.49; 2 studies; 339 cases/1455 controls) was non-significant. HAP was associated with cervical neoplasia among studies that accounted for HPV infection (OR = 9.60; 95% CI = 3.79-24.32) and smoking (OR = 4.72; 95% CI = 1.84-12.07). Similarly, our observed associations between HAP and upper aero-digestive tract cancers remained significantly elevated when analyses were restricted to studies that controlled for smoking. No significant publication bias was detected. Our results suggest that the carcinogenic effect of HAP observed for lung cancer may extend to other cancers, including those of the cervix and the upper aero-digestive tract. Further research is needed to confirm these associations in prospective studies.

Hepatitis B spliced protein (HBSP) promotes the carcinogenic effects of benzo [alpha] pyrene by interacting with microsomal epoxide hydrolase and enhancing its hydrolysis activity

BACKGROUND

The risk of hepatocellular carcinoma (HCC) increases in chronic hepatitis B surface antigen (HBsAg) carriers who often have concomitant increase in the levels of benzo[alpha]pyrene-7,8-diol-9,10-epoxide(±) (BPDE)-DNA adduct in liver tissues, suggesting a possible co-carcinogenesis of Hepatitis B virus (HBV) and benzo[alpha]pyrene in HCC; however the exact mechanisms involved are unclear.

METHODS

The interaction between hepatitis B spliced protein (HBSP) and microsomal epoxide hydrolase (mEH) was confirmed using GST pull-down, co-immunoprecipitation and mammalian two-hybrid assay; the effects of HBSP on mEH-mediated B[alpha]P metabolism was examined by high performance liquid chromatography (HPLC); and the influences of HBSP on B[alpha]P carcinogenicity were evaluated by bromodeoxyuridine cell proliferation, anchorage-independent growth and tumor xenograft.

RESULTS

HBSP could interact with mEH in vitro and in vivo, and this interaction was mediated by the N terminal 47 amino acid residues of HBSP. HBSP could greatly enhance the hydrolysis activity of mEH in cell-free mouse liver microsomes, thus accelerating the metabolism of benzo[alpha]pyrene to produce more ultimate carcinnogen, BPDE, and this effect of HBSP requires the intact HBSP molecule. Expression of HBSP significantly increased the formation of BPDE-DNA adduct in benzo[alpha]pyrene-treated Huh-7 hepatoma cells, and this enhancement was blocked by knockdown of mEH. HBSP could enhance the cell proliferation, accelerate the G1/S transition, and promote cell transformation and tumorigenesis of B[alpha]P-treated Huh-7 hepatoma cells.

CONCLUSIONS

Our results demonstrated that HBSP could promote carcinogenic effects of B[alpha]P by interacting with mEH and enhancing its hydrolysis activity.

Planning cancer control in Latin America and the Caribbean

Non-communicable diseases, including cancer, are overtaking infectious disease as the leading health-care threat in middle-income and low-income countries. Latin American and Caribbean countries are struggling to respond to increasing morbidity and death from advanced disease. Health ministries and health-care systems in these countries face many challenges caring for patients with advanced cancer: inadequate funding; inequitable distribution of resources and services; inadequate numbers, training, and distribution of health-care personnel and equipment; lack of adequate care for many populations based on socioeconomic, geographic, ethnic, and other factors; and current systems geared toward the needs of wealthy, urban minorities at a cost to the entire population. This burgeoning cancer problem threatens to cause widespread suffering and economic peril to the countries of Latin America. Prompt and deliberate actions must be taken to avoid this scenario. Increasing efforts towards prevention of cancer and avoidance of advanced, stage IV disease will reduce suffering and mortality and will make overall cancer care more affordable. We hope the findings of our Commission and our recommendations will inspire Latin American stakeholders to redouble their efforts to address this increasing cancer burden and to prevent it from worsening and threatening their societies.

Parity as a cofactor for high-grade cervical disease among women with persistent human papillomavirus infection: a 13-year follow-up

Background:

Several environmental factors have been associated with increased risks for cervical cancer. We examined whether reproductive history, contraceptive use, or sexual behaviour increase the risk for cervical intraepithelial neoplasia grade 3 or worse (CIN3+) among women with persistent human papillomavirus (HPV) infection.

Methods:

A population-based cohort of women participated in a personal interview and underwent a gynaecological examination at which cervical specimens were obtained for HPV DNA testing. Follow-up information (∼13 years) on cervical lesions was obtained from the Danish Pathology Data Bank. Women who had a high-risk HPV infection comprised the overall study population (n=1353). A subgroup of women with persistent high-risk HPV infection (n=312) was identified. Hazard ratios (HRs) for a diagnosis of CIN3+ and the corresponding 95% confidence intervals (CIs) were calculated.

Results:

Women with persistent HPV infection who had given birth had a significantly increased risk for CIN3+ (HR=1.78; 95% CI: 1.07–2.94). No association was found with pregnancy, use of intrauterine devices, or sexual behaviour. Based on small numbers, women with persistent HPV infection had a decreased risk for CIN3+ with any use of oral contraceptives (HR=0.54; 95% CI: 0.29–1.00).

Conclusion:

Childbirth increases the risk for subsequent CIN3+ among women with persistent HPV infection.

Detection by PCR of human papillomavirus in Colombia: Comparison of GP5+/6+ and MY09/11 primer sets

The aims of this study were to determine the prevalence of HPV infection and evaluate the concordance and performance of two primer sets for detecting single and multiple viral infections. A total of 1810 Colombian women were enrolled in the study, and molecular, cytological and epidemiological analyses were performed. Both concordance and performance of two different PCR amplification primer sets (GP5+/6+ and MY09/11) were assessed. The results showed that 60.2% of females with positive HPV DNA were infected by more than one viral type. The OR for multiple infections was 18.2 when using the MY09/11 primer set and 6.52 with the GP5+/6+ primer set. The results also showed an association between GP5+/6+ positivity and the severity of the disease regarding the cytological findings. It was also found that using a single primer set led to underestimating the prevalence for HPV infection. The simultaneous use of these primer sets is an important tool for the detection of HPV DNA, being equally relevant for identifying multiple infections and low viral DNA copies. This study highlights the importance of suitable assessment of HPV epidemiological profiles; screening programs must also be strengthened to broaden the coverage of the most vulnerable populations.

Smoking and cervical cancer

Cervical cancer (CC) is the third most common cancer in women worldwide; however, CC is a preventable disease, and much effort should be done to prevent it. Persistence of high-risk HPV infection is the strongest epidemiologic risk factor for CC, however it is not sufficient for development of the disease it cofactors should be present. In 2004; IARC listed cervical cancer among those causally related to smoking. Smoking interferes with incidence and prevalence of HPV infection and is associated with cervical intraepithelial neoplasia and invasive CC. Multiple factors seem to intervene on cervical carcinogenesis related with tobacco, especially by direct local carcinogenic effect and local immunosuppression. Smoking addition is also closely related with other confounding factors, like unfavorable psychosocial events, systemic immunity, contraception, and nutrition, which got difficult epidemiologic evaluation of smoking role on cervical carcinogenesis. Smoking habits should be taken in account in clinical practice and in research concerning CC.

Human papillomavirus infection in Honduran women with cervical intraepithelial neoplasia or cervical cancer

OBJECTIVES

The aims of this study were to investigate human papillomavirus (HPV) genotypes in women with cervical intraepithelial lesions and cervical cancer (CC) in Honduras and to identify epidemiological cofactors that contribute to the development of CC.

METHODS

Among the 289 patients analyzed, 139 had low-grade squamous intraepithelial lesion (LSIL), 60 had high-grade squamous intraepithelial lesion (HSIL), and 90 had CC.

RESULTS

The HPV DNA was detected in 113 women (81%) with LSIL, in 58 women (97%) with HSIL, and in 84 women (93%) with CC. Twenty-five HPV genotypes were found. Human papillomavirus type 16 was detected in 41% of women with CC, in 35% of women with HSIL, and in 24% of women with LSIL. Human papillomavirus type 18 was found in 9% of women with CC, in 4% of women with HSIL, and 5% of women with LSIL.

CONCLUSION

Therefore, implementation of the prophylactic vaccines against HPV genotypes 16 and 18 has the potential of preventing at least a quarter of LSIL, one third of HSIL, and about half of CC cases in Honduras.

Indian women with higher serum concentrations of folate and vitamin B12 are significantly less likely to be infected with carcinogenic or high-risk (HR) types of human papillomaviruses (HPVs)

Background:

Studies conducted in the USA have demonstrated that micronutrients such as folate and vitamin B12 play a significant role in modifying the natural history of high-risk human papillomaviruses (HR-HPVs), the causative agent for developing invasive cervical cancer (CC) and its precursor lesions.

Objective:

The purpose of the current study was to investigate whether these micronutrients have similar effects on HR-HPV infections in Indian women.

Methods:

The associations between serum concentrations of folate and vitamin B12 and HR-HPV infections were evaluated in 724 women who participated in a CC screening study in the southern state of Andhra Pradesh, India. Serum folate and vitamin B12 concentrations were measured by using a competitive radio-binding assay. Digene hybrid capture 2 (HC2) assay results were used to categorize women into two groups, positive or negative for HR-HPVs. Unconditional logistic regression models specified a binary indicator of HC2 (positive/negative) as the dependent variable and serum folate concentrations combined with serum vitamin B12 concentrations as the independent predictor of primary interest. Models were fitted, adjusting for age, education, marital status, parity, type of fuel used for cooking and smoking status.

Results:

Women with higher concentrations of serum folate (>6 ng/mL) and vitamin B12 (>356 pg/mL) were at lower risk of being positive for HR-HPVs compared to those with serum folate ≤6 ng/mL and serum vitamin B12 ≤ 356 pg/mL (odds ratio = 0.26; 95% confidence interval: 0.08–0.89; P = 0.03).

Conclusions:

These results demonstrated that improving folate and vitamin B12 status in Indian women may have a beneficial impact on the prevention of CC. Micronutrient based interventions for control of HR-HPV infections may represent feasible alternatives to vaccine based approaches to HPV disease prevention, which are currently unaffordable for use in resource limited areas in rural India.

Joint disease mapping of cervical and male oropharyngeal cancer incidence in blacks and whites in South Carolina

Human papillomavirus (HPV) infection is an established causal agent for cervical cancer and a subset of oropharyngeal cancers. It is hypothesized that orogenital transmission results in oral cavity infection. In this paper we explore the geographical association between cervical and male oropharyngeal cancer incidence in blacks and whites in South Carolina using Bayesian joint disease mapping models fit to publicly available data. Our results suggest weak evidence for county-level association between the diseases, and different patterns of joint disease behavior for blacks and whites.

Human papillomavirus infection in Honduran women with normal cytology

Objective

This study was aimed at estimating type-specific HPV prevalence and its cofactors among Honduran women with normal cytology in order to provide valuable information to health policymakers about the epidemiology of this important sexually transmitted infection.

Methods

A total of 591 women with normal cytology from Tegucigalpa, Honduras were interviewed and tested for HPV using the SPF10 LiPA25. A structured epidemiological questionnaire was administered to each woman.

Results

The overall HPV prevalence was 51%. Twenty-three types of HPV were detected; HPV 16, 51, 31, 18, and 11 were the most common. The highest prevalence of cancer associated HPV types (15.0%) was found in the women less than 35 years. Besides the association with age, the main independent predictors of HPV infection were the lifetime number of sexual partners and having a low socioeconomic status and less than 5 previous Pap smears.

Conclusions

In the population studied, there was a broad diversity of HPV infections, with high-risk types being the most common types detected. The establishment of a well-characterized population with regard to the community prevalence of type-specific HPV infection will provide a valuable baseline for monitoring population effectiveness of an HPV vaccine.

Age-specific prevalence of infection with human papillomavirus in females: a global review

PURPOSE

Global data on age-specific prevalence of human papillomavirus (HPV) infection overall, and for high-risk HPV types 16 and 18, are essential for the future implementation of HPV prophylactic vaccines for cervical cancer prevention.

METHODS

A systematic review of peer-reviewed publications was conducted to summarize worldwide data on genital HPV-DNA prevalence in women. Studies with clear descriptions of polymerase chain reaction or hybrid capture detection assays were included.

RESULTS

A total of 346,160 women were included in 375 studies. Of 134 studies with age-stratified HPV prevalence data (116 low sexual risk populations, 18 high sexual risk populations), over 50% were from Europe and the Middle East (38%) and North America (19%), with smaller proportions from Asia and Australia (21%), Central and South America (11%), and Africa (10%). Across all geographical regions, data on HPV prevalence were generally limited to women over 18 years of age. Consistently across studies, HPV infection prevalence decreased with increasing age from a peak prevalence in younger women (< or =25 years of age). In middle-aged women (35-50 years), maximum HPV prevalence differed across geographical regions: Africa (approximately 20%), Asia/Australia (approximately 15%), Central and South America (approximately 20%), North America (approximately 20%), Southern Europe/Middle East (approximately 15%), and Northern Europe (approximately 15%). Inconsistent trends in HPV prevalence by age were noted in older women, with a decrease or plateau of HPV prevalence in older ages in most studies, whereas others showed an increase of HPV prevalence in older ages. Similar trends of HPV 16 and/or 18 prevalence by age were noted among 12 populations with available data.

DISCUSSION

Genital HPV infection in women is predominantly acquired in adolescence, and peak prevalence in middle-aged women appears to differ across geographical regions. Worldwide variations in HPV prevalence across age appear to largely reflect differences in sexual behavior across geographical regions. Further studies of HPV prevalence in adolescents are needed for all geographic regions.

Comparison of visual inspection and Papanicolau (PAP) smears for cervical cancer screening in Honduras: should PAP smears be abandoned?

OBJECTIVE

To compare visual inspection with acetic acid (VIA) to Papanicolau (PAP) smears in a community setting in a developing nation.

METHODS

Women undergoing cervical cancer screening in Honduras received either VIA and PAP smears (VIA/PAP group) or PAP smears alone (PAP-only group). Local healthcare providers performed PAP screening. A VIA-trained nurse performed VIA exams. All PAP smears were processed in Honduras. PAP smears from the VIA/PAP group were reviewed in the United States. Women with positive VIA or PAP tests were offered colposcopy. We compared the relative accuracy of PAP smears and VIA and the proportions of women completing follow-up colposcopy after positive screening tests.

RESULTS

In total, 1709 PAP smears were performed including women from both the VIA/PAP and PAP-only groups. Nine PAP smears were positive (0.5%). Three women completed colposcopy (33%). All three had biopsy-confirmed dysplasia. In the VIA/PAP group (n = 339), 49 VIA exams were abnormal (14%) and two PAP smears were abnormal when read in Honduras (0.6%). When reviewed in the United States, 14 of the 339 PAP smears were abnormal (4%). Forty women (83%) completed follow-up colposcopy after a positive VIA exam. Twenty-three had biopsy-proven dysplasia. All 23 dysplasia cases had negative PAP smear readings in Honduras; four PAP smears were reclassified as positive in the United States.

CONCLUSIONS

Although few developing countries can maintain high-quality PAP smear programmes, many governments and charitable organizations support cervical cancer screening programmes that rely on PAP smears. This study underscores the need to promote alternative technologies for cervical cancer screening in low-resource settings.

Decreased prevalence of dysplasia in high-risk population immigrants in a low-risk area for cervical cancer

Incidence rates of cervical cancer and its precursors vary considerably, with the highest rates found in developing countries. Differences are influenced by endogenous and exogenous factors. Comparing cytologic abnormality incidence rates from a high-risk population in the original high-risk area, with those of women from this high-risk population who have immigrated to a low-risk area could give insight in the significance of endogenous versus environmental factors. Smears collected from Surinamese women attending the Surinamese screening program and smears collected from immigrant Surinamese women attending the Dutch screening program were cytologically analyzed using the Dutch microscopical coding system KOPAC. Statistical analysis was performed by using logistic regression to calculate (age-adjusted) odds ratios (ORs). The age-adjusted ORs of having dysplasia were higher for Surinamese women living in Suriname versus Surinamese immigrant women and increased with increasing P-scores: 0.77 (0.31-1.91) for borderline changes, 1.62 (0.58-4.57) for mild dysplasia, and 3.20 (1.55-6.60) for moderate to severe dysplasia/neoplasia. We conclude that fewer cases with dysplasia are present in a high-risk population that has immigrated to a low-risk area for cervical cancer than in the high-risk population continuously living in a high-risk area. This finding emphasizes the importance of environmental factors.

A built-in co-carcinogenic effect due to viruses involved in latent or persistent infections

A new hypothesis for some cancers, which combines the chromosomal instability theories with a co-carcinogenic effect of viruses causing latent or persistent infection, is presented. The hypothesis incorporates the multi-step model of cancer and that pre-cancerous cells reach a state of chromosomal instability. Because of chromosomal instability, the genome of these cell lines will lead to changes from generation to generation and will face a remarkable selection pressure both from lost traits, apoptosis, and from the immune system. Viruses causing latent or persistent infections have evolved many different genes capable to evade the immune system. If these viruses are harboured in the genome of pre-cancerous cells they could provide them with "superpowers" and with genes that may assist the cells to elude the immune system. The theory explains why cancer predominantly is a disease of old age. Upon aging, the immune system becomes reduced including the ability to control and suppress the viruses that cause latent or persistent infections. The risk of cancer could thereby increase as the immune functions decrease. The theory provides new insights to the genesis of cancers.

Prevalence and risk factors of HPV infection among high-risk rural and urban Lithuanian women

AIMS

To investigate the prevalence, persistence and risk factors of high oncogenic risk human papillomavirus (HPV) among urban and rural women of reproductive age coming to consult a gynaecologist.

METHODS

A prospective cohort study in urban (Kaunas) and rural (Marijampole) regions of Lithuania. The data were collected in 8 healthcare institutions from women seeking consultation of gynaecologists using a questionnaire for finding out demographic, social, behavioural and biomedical factors. HPV DNA was determined by molecular hybridization method (hybrid capture version II) determining HPV of high oncogenic risk.

RESULT

1,120 women participated in the study. The prevalence of high-risk HPV among the studied women was 25.1%. It was higher among the urban women than among the rural women. The prevalence of high-risk HPV was increased if the subjects had 2 or more sexual partners during the last 12 months (OR 2.81; 95% CI 1.83-4.32), were 19 years of age or younger (OR 2.68; 95% CI 1.47-4.91), were smoking (OR 1.81; 95% CI 1.16-2.81), and had secondary or lower education level (OR 1.43; 95% CI 1.01-2.04). This infection was obviously associated with high- and low-grade squamous intraepithelial changes of the cervix (OR 1.66, 95% CI = 1.08-2.53).

CONCLUSION

The incidence rate for cervical cancer in Lithuania is one of the highest in comparison with other European countries. HPV infection was also particularly common in the studied population. About one-fourth of the women were infected with high-risk HPV infection. Young and less educated women were found to be the group that was most exposed to HPV, and therefore public health interventions and education seem to be essential in programs aimed at reducing the incidence of cervical cancer.

Primary prevention of human papillomavirus-dependent neoplasia: No condom, no sex

Cervix cancer is one of several neoplastic disorders that arise following transfer of human papillomavirus (HPV) during unprotected sexual intercourse, and like most other sexually transmitted diseases (STDs), is largely preventable by consistent condom use. This primary prevention strategy has received little support, however, when compared with massive secondary prevention initiatives involving cervical screening. The reasons for this anomalous situation are complex, and include: (i) the asymptomatic nature of most primary HPV infections; (ii) widespread ignorance concerning the venereal aetiology of HPV-related cancers; (iii) the common but incorrect belief that condom use does not reduce HPV transmission; (iv) the perceived irrelevance of safe sex campaigns based on reducing transmission of human immunodeficiency virus (HIV) in high-HPV but low-HIV countries such as the Philippines; (v) the promotion of oral contraception by the medical and pharmaceutical sectors as the sexual prophylaxis of choice; and (vi) the assumption that HPV vaccines will solve the problem. Here it is proposed that the high prevalence of non-HIV STDs, including distressing disorders such as genital warts and herpes simplex, can be exploited with greater efficacy as a public health deterrent to unsafe sex and HPV transmission. Targeting a "mutually assured infection" campaign at vulnerable subgroups such as teenagers and oral contraceptive users could help reverse the global expansion of HPV-related cancers.

Viruses, chemicals and co-carcinogenesis

The etiology of cancers appears to be complex and multifactorial. Peyton Rous and others demonstrated the process of co-carcinogenesis by exposing rabbits to a virus and tars. Epidemiologists have proposed virus-chemical interactions to cause several cancers. For example, one might propose that the etiology of cervical cancer results from a complex interplay between oncogenic viruses and cervical tar exposures through tar-based vaginal douching, cigarette smoking, and/or long-term cooking over wood-burning stoves in poorly ventilated kitchens. Hepatocellular carcinoma may result from the joint effects of viruses and hepatotoxic chemical carcinogens. Kaposi's sarcoma might happen following reciprocal actions of human herpes virus-8 infection, immunosuppression, and chemical exposures, such as nitrite radicals and alumino-silicates. Use of Koch's postulates will not help one prove or disprove a multifactorial causation of disease; new criteria are needed. Delineating the web of causation may lead to additional strategies for prevention and treatment of several cancers.

Cigarette smoking and cervical cancer: Part I: a meta-analysis

Cancer of the cervix is the third most common cancer among women worldwide and its etiology is not clearly understood. Human papillomavirus can be found in approximately 95% of cervical cancers, but it does not appear to be necessary or sufficient to induce malignancy. In 1977, Winkelstein suggested that cigarette smoking was a causative factor in the development of cervical cancer. We report a meta-analysis of cigarette smoking and cervical disease and conclude that the data support a role for cigarette smoking as a risk factor for cervical cancer. We propose a multifactorial hypothesis involving a virus-tar interaction as the etiology of cervical cancer.

The viral etiology of cervical cancer

Epidemiological studies supported by molecular technology have provided sufficient evidence on the causal role of some Human Papillomavirus (HPV) infections in the development of cervical cancer. This association has been evaluated under all proposed sets of causality criteria and endorsed by the scientific community and major review institutes. HPV has been proposed as the first-ever identified, necessary cause of a human cancer. In practical terms, the concept of a necessary cause implies that cervical cancer does not and will not develop in the absence of the persistent presence of HPV-deoxyribonucleic acid (DNA). This important advancement has two practical implications in prevention. Firstly, screening programs can be enhanced if HPV testing is judiciously incorporated into solving the fraction of ambiguous cytology readings. In some populations HPV screening as a primary test may prove to be the strategy of choice. Secondly, like in the hepatitis B disease model, intense efforts are currently being put into the development and testing of vaccines that may prevent the relevant HPV infections, and presumably, cervical cancer. At this stage of development, regulatory agencies are requested to evaluate the scientific evidence and weigh its implications in relation to costs, public health investments and policy. This is a subjective evaluation that could be guided by a careful description of the most relevant studies and findings.

Environmental co-factors in HPV carcinogenesis

Epidemiological studies have shown that only a small fraction of women infected with oncogenic HPV types will eventually progress to high-grade intraepithelial lesions (HSIL) and cervical cancer (CC). Because infection by oncogenic HPVs is a necessary but not a sufficient cause of CC, it has been assumed that other factors, acting in conjunction with HPV, influence the risk of transition from cervical HPV infection to cervical malignancy. This paper reviews the epidemiological evidence for the role of environmental co-factors in HPV carcinogenesis as assessed from selected studies that report associations within a well-defined HPV-DNA positive group. Co-factors assessed include parity, use of oral contraceptives, tobacco smoking, infection with other sexually transmitted diseases, and dietary and nutritional factors. Based on the evidence provided by the largest epidemiological studies that using sensitive detection methods allowed for the effects of HPV, it can be concluded that, among HPV positive women, high parity, long-term OC use, smoking, and co-infection with other sexually transmitted agents are the most consistently identified environmental co-factors likely to influence the risk of progression from cervical HPV infection to HSIL and invasive CC. There is limited evidence for a role of dietary factors in HPV carcinogenesis. On-going epidemiological studies will shed more light into the role of these and other co-factors, but if confirmed, these conclusions may imply that multiparous women, women who are smokers, and women on long-term OC use, might need a closer cytological and HPV surveillance than women in the general population.

The causal relation between human papillomavirus and cervical cancer

The causal role of human papillomavirus infections in cervical cancer has been documented beyond reasonable doubt. The association is present in virtually all cervical cancer cases worldwide. It is the right time for medical societies and public health regulators to consider this evidence and to define its preventive and clinical implications. A comprehensive review of key studies and results is presented.

Burning wood in the kitchen increases the risk of cervical neoplasia in HPV-infected women in Honduras

There is suggestive evidence that the use of wood for cooking increases the risk of invasive cervical cancer. We investigated this association in women with cervical neoplasia in Honduras. Women aged 20-64 years with cervical intraepithelial neoplasia (CIN) grade I (n = 44), CIN II (n = 36) or CIN III (n = 45) were recruited from screening programs in Tegucigalpa City and each was matched by age and clinic to 2 controls (241 total) without cervical abnormalities. The clinics selected women of low socioeconomic status. Cervical scrapes were tested for the presence of human papillomavirus (HPV) DNA using a general primer set directed against the L1 open reading frame, and HPV genotyping was performed. Odds ratios (ORs) were computed through conditional logistic regression; p-values were from tests for linear trend of risk with increasing exposure. HPV DNA was detected in 48% of women with CIN I, 67% with CIN II and 89% with CIN III. The ORs were 1.5, 2.5 and 38.3 respectively. At univariate analysis, age at first intercourse was consistently lower among cases than controls. Risk was reduced by 50% or more in all 3 CIN classes when initiation of sexual activity at age 20 years or older was compared with initiation before age 16 years (p = 0.013 for CIN I). No effect was observed for smoking, oral contraceptives or previous cytologic screening. Effects for number of sexual partners, parity, age at first pregnancy and education were in the expected directions but never persisted after adjustment for HPV. Chronic exposure to wood smoke significantly increased the risk of CIN III (p = 0.022). However, women who said "No" when asked if they ever used wood in the kitchen had a higher risk than those with low or intermediate exposure. This was taken as evidence that the initial screening question had either been misunderstood or that answers were biased. Restricting the analysis to women who reported exposure yielded positive associations in all CIN classes with for CIN III ORs of 2.3 for 25-34 and 9.5 for 35+ years compared with women who had 1-14 years of exposure (p = 0.017). A multivariate analysis of the complete dataset (n = 366) allowed for separate ORs for HPV in each CIN class. Inclusion of age at first intercourse significantly improved this model (p = 0.021). Adding exposure to wood smoke further improved the model only if an interaction between woodsmoke and HPV was allowed for. If, as the data suggest, it was assumed that wood smoke had its effect among HPV-positives only, there was a significant linear dose-response relationship between exposure to woodsmoke and risk of CIN (p = 0.026). This association was independent of other risk factors including education, parity and number of sexual partners. ORs in the final model were 0.37 for age at first intercourse 20 years or higher and 5.69 for more than 35 years of exposure to wood burning in the kitchen. The present study suggests that the use of wood for cooking is a risk factor for cervical neoplasia that deserves further study, given its high prevalence in developing countries.