Reproductive factors in relation to ovarian cancer: a case-control study in Northern Vietnam

Lifetime ovulatory years and risk of epithelial ovarian cancer: a multinational pooled analysis

BACKGROUND

The role of ovulation in epithelial ovarian cancer (EOC) is supported by the consistent protective effects of parity and oral contraceptive use. Whether these factors protect through anovulation alone remains unclear. We explored the association between lifetime ovulatory years (LOY) and EOC.

METHODS

LOY was calculated using 12 algorithms. Odds ratios (ORs) and 95% confidence intervals (CIs) estimated the association between LOY or LOY components and EOC among 26 204 control participants and 21 267 case patients from 25 studies. To assess whether LOY components act through ovulation suppression alone, we compared beta coefficients obtained from regression models with expected estimates assuming 1 year of ovulation suppression has the same effect regardless of source.

RESULTS

LOY was associated with increased EOC risk (OR per year increase = 1.014, 95% CI = 1.009 to 1.020 to OR per year increase = 1.044, 95% CI = 1.041 to 1.048). Individual LOY components, except age at menarche, also associated with EOC. The estimated model coefficient for oral contraceptive use and pregnancies were 4.45 times and 12- to 15-fold greater than expected, respectively. LOY was associated with high-grade serous, low-grade serous, endometrioid, and clear cell histotypes (ORs per year increase = 1.054, 1.040, 1.065, and 1.098, respectively) but not mucinous tumors. Estimated coefficients of LOY components were close to expected estimates for high-grade serous but larger than expected for low-grade serous, endometrioid, and clear cell histotypes.

CONCLUSIONS

LOY is positively associated with nonmucinous EOC. Differences between estimated and expected model coefficients for LOY components suggest factors beyond ovulation underlie the associations between LOY components and EOC in general and for non-HGSOC.

Lifetime ovulations and epithelial ovarian cancer risk and survival: A systematic review and meta-analysis

OBJECTIVE

To assess the relationship between lifetime ovulatory years (LOY) and Epithelial ovarian cancer (EOC) risk and survival.

METHODS

A systematic review was performed in accordance with PRISMA guidelines. Relevant studies were identified from PubMed, MEDLINE, and Embase through December 31, 2021 combining the following search: [("ovulation" or "ovulation cycles" or "ovulatory age" or "ovulatory cycles") and ("ovarian cancer" or "ovarian neoplasms") and ("humans" and "female")]. Reference lists of identified articles were searched for additional studies. Studies were excluded from consideration if they were not a published, peer-review article; not in English; lacked data on effect sizes; had data included in another publication; or were a review article, cross-sectional study, or case report. Two independent investigators screened abstracts and full texts for eligibility, extracted study-level data, and assigned study quality. Disagreements between abstractors were discussed and resolved by consensus.

RESULTS

Thirty-one reports were included in the qualitative review of LOY and EOC risk, inclusive of 24 studies with sufficient data to be included in the meta-analysis. Women with the highest level of LOY had 2.26 times higher odds of EOC than women with the lowest level of LOY (95% CI 1.94-2.83). LOY was associated with risk of serous (pooled OR 2.31, 95% CI 1.60-3.33) and endometrioid tumors (pooled OR 3.05, 95% CI 2.08-4.45) but not mucinous disease (pooled OR 1.52, 95% CI 0.87-2.64). There were only four studies examining the LOY-survival association, which precluded a quantitative assessment; however, three of the published studies reported worse outcome with greater LOY.

CONCLUSION

LOY is a risk factor for specific EOC histotypes and may also influences EOC survival. Standard definitions of LOY, participant-level data, and larger sample size will enable more precise quantitation of the LOY-EOC association, which can inform EOC risk assessment models.

The preventive effect of breastfeeding against ovarian cancer in BRCA1 and BRCA2 mutation carriers: A systematic review and meta-analysis

OBJECTIVE

A recent study showed that even a few months of breastfeeding is associated with a significant decrease in the risk of ovarian cancer in the general population. This study aimed to perform a systematic review and meta-analysis to determine the significance of the length of the breastfeeding period on ovarian cancer risk in BRCA1/2 mutation carriers.

METHODS

PubMed, EMBASE, and Cochrane databases were searched up to June 1, 2021. We included case-control and cohort studies that contained information on breastfeeding and the risk of ovarian cancer in BRCA1/2 mutation carriers. Odds ratios (OR) were meta-analytically pooled using a fixed-effects model.dd RESULTS: Five studies, including one cohort study and four case-control studies, were included in this meta-analysis. Of the 14,601 BRCA1/2 mutation carriers, the overall pooled OR of ever having performed breastfeeding in patients who had ovarian cancer was 0.767 (95% confidence interval [CI], 0.688-0.856) and 0.817 (95% CI, 0.650-1.028) for patients with BRCA1 and BRCA2 mutation, respectively. Breastfeeding for >1 year acted as a protective factor in both BRCA1 [OR: 0.787 (95% CI, 0.682-0.907)] and BRCA2 [OR: 0.567 (95% CI, 0.400-0.802)] mutation carriers. No significant heterogeneity was present (I2 = 0%), and the funnel plot was also properly distributed, showing no publication bias.

CONCLUSIONS

Breastfeeding is a preventive, modifiable factor for ovarian cancer in BRCA1/2 mutation carriers. Ever having performed breastfeeding was significantly preventive for ovarian cancer in the BRCA1 mutation carriers, however a period of 1 year or more of breastfeeding is required for a reduced ovarian cancer risk in BRCA2 mutation carriers.

Intrauterine device use and risk of ovarian cancer: Results from the New England Case-Control study and Nurses' Health Studies

Results of studies assessing intrauterine device (IUD) use and ovarian cancer risk are inconsistent. We examined the association between IUD use, including duration, type and timing of use, and ovarian cancer risk using three population-based studies. Data from the New England Case-Control Study (NEC) and two prospective cohort studies, the Nurses' Health Studies (NHS/NHSII), were included in the analysis. Information on IUD use was collected by in-person interview in NEC and by biennial questionnaire in NHS/NHSII. We used unconditional logistic regression to calculate odds ratios (OR) and 95% confidence intervals (CI) in NEC and Cox regression to calculate hazard ratios (HR) and 95% CI in NHS/NHSII. We used meta-analysis to combine the NEC and the pooled NHS/NHSII results. Overall, IUD use was not associated with epithelial ovarian cancer risk (OR = 0.96, 95% CI: 0.81-1.14 in NEC; HR = 0.89, 95% CI: 0.69-1.15 in NHS/NHSII; combined RR = 0.94, 95% CI: 0.81-1.08). Among IUD users, older age at first use was associated with increased ovarian cancer risk (P-trend = .03). We did not observe significant associations by IUD type or duration of use. In conclusion, IUD use was not associated with ovarian cancer risk in our study.

Ever-use of the intra-uterine device and the risk of ovarian cancer

The association between the use of the intra-uterine device (IUD) and the risk of ovarian cancer is not well known. In this study, we sought to determine whether the use of an IUD is associated with a reduction in the risk of ovarian cancer. We searched Medline, EMBASE, Google Scholar, Scopus, ISI Web of Science and Cochrane database search, as well as PubMed (www.pubmed.gov) and RCT registry (www.clinicaltrials.gov) until the end of June 2019 to conduct a systematic review and meta-analysis comparing ever-use vs. never-use of an IUD and the risk of subsequent ovarian cancer. We obtained 431 records, of which 9 met inclusion criteria. A total of five case-control studies and four cohort studies were retrieved to establish the risk of ovarian cancer amongst ever-users of an IUD. Relative to the never-use of the IUD, ever-use conferred a lower risk of ovarian cancer with an estimated OR of 0.67 95% CI [0.60 - 0.74], p < .0001, I² = 71%. This relationship remained significant when results were restricted to studies evaluating the levonorgestrel intrauterine system (LNG-IUD) alone, with an estimated OR of 0.58 95% CI [0.47 - 0.71], p < .0001, I² = 0%, as well as when the analysis was stratified by study design, with an OR of 0.64 95% CI [0.56 - 0.74] for case-control studies, and OR of 0.71 95% CI [0.60 - 0.84] for cohort studies (p < .0001). Ever-use of an intrauterine contraceptive device reduces the risk of ovarian cancer by an average of 30%. Whether differences exist for duration of use, use of type-specific device, and specific tumour type needs to be addressed in future studies.Impact statementWhat is already known on this subject? The use of IUDs is very common practice in today's society. Its benefits regarding contraception, the treatment of abnormal uterine bleeding and even the reduction of the rates of endometrial cancer are well established. However, whether IUD's are associated with a reduction in the risk of ovarian cancer is unknown.What do the results of this study add? In this study, we show that the ever-use of the IUD reduces the risk of ovarian cancer by an average of 30%. We provide insight regarding the potential theories that may underlie these findings.What are the implications of these findings for clinical practice and/or further research? future studies will need to determine whether the beneficial effects found are a function of duration of use, of type-specific device, or specific tumour types. In the meantime, these findings may serve clinicians to reassure and counsel patients about the added benefits of intra-uterine devices.

Association Between Breastfeeding and Ovarian Cancer Risk

Importance

Breastfeeding has been associated with a reduced risk of epithelial ovarian cancer in multiple studies, but others showed no association. Whether risk reduction extends beyond that provided by pregnancy alone or differs by histotype is unclear. Furthermore, the observed associations between duration and timing of breastfeeding with ovarian cancer risk have been inconsistent.

Objective

To determine the association between breastfeeding (ie, ever/never, duration, timing) and ovarian cancer risk overall and by histotype.

Design, Setting, and Participants

A pooled analysis of parous women with ovarian cancer and controls from 13 case-control studies participating in the Ovarian Cancer Association Consortium was performed. Odds ratios (ORs) and 95% CIs of the overall association were calculated using multivariable logistic regression and polytomous logistic regression for histotype-specific associations. All data were collected from individual sites from November 1989 to December 2009, and analysis took place from September 2017 to July 2019.

Exposures

Data on breastfeeding history, including duration per child breastfed, age at first and last breastfeeding, and years since last breastfeeding were collected by questionnaire or interview and was harmonized across studies.

Main Outcomes and Measures

Diagnosis of epithelial ovarian cancer.

Results

A total of 9973 women with ovarian cancer (mean [SD] age, 57.4 [11.1] years) and 13 843 controls (mean [SD] age, 56.4 [11.7] years) were included. Breastfeeding was associated with a 24% lower risk of invasive ovarian cancer (odds ratio [OR], 0.76; 95% CI, 0.71-0.80). Independent of parity, ever having breastfed was associated with reduction in risk of all invasive ovarian cancers, particularly high-grade serous and endometrioid cancers. For a single breastfeeding episode, mean breastfeeding duration of 1 to 3 months was associated with 18% lower risk (OR, 0.82; 95% CI, 0.76-0.88), and breastfeeding for 12 or more months was associated with a 34% lower risk (OR, 0.66; 95% CI, 0.58-0.75). More recent breastfeeding was associated with a reduction in risk (OR, 0.56; 95% CI, 0.47-0.66 for <10 years) that persisted for decades (OR, 0.83; 95% CI, 0.77-0.90 for ≥30 years; P for trend = .02).

Conclusions and Relevance

Breastfeeding is associated with a significant decrease in risk of ovarian cancer overall and for the high-grade serous subtype, the most lethal type of ovarian cancer. The findings suggest that breastfeeding is a potentially modifiable factor that may lower risk of ovarian cancer independent of pregnancy alone.

Intrauterine Device Use and Ovarian Cancer Risk: A Systematic Review and Meta-analysis

OBJECTIVE

To explore the relationship between intrauterine device (IUD) use and risk of ovarian cancer through systematic review of the literature and meta-analysis.

DATA SOURCES

We searched MEDLINE, EMBASE, Cochrane Library, Web of Science Core Collection from inception to June 2018. For the MEDLINE search, we included the MeSH terms "intrauterine devices" AND "ovarian neoplasms," however also searching "intrauter*," "ovar*" and "fallopian tube," as well as "cancer" and "carcinoma" as keywords to include all possible variations. Similar search terms were used in the other databases. We also searched ClinicalTrials.gov.

METHODS OF STUDY SELECTION

Case-control and cohort studies that collected individual level data on IUD use and ovarian cancer diagnosis were critically reviewed and data extracted. Review of abstracts from 399 articles through systematic database review and an additional 200 articles through Google Scholar identified a total of 15 studies with individual level data regarding IUD use and incident ovarian cancer. On critical review, 11 of these studies were used for meta-analysis. All case reports and reviews were excluded.

TABULATION, INTEGRATION, AND RESULTS

The data were harmonized and weighted and summary odds ratios (ORs) were calculated. Covariates were identified evaluated separately. A random-effects meta-analysis was performed to confirm minimal bias. Harmonization and weighting of the data revealed an OR association between ever use of an IUD and incident ovarian cancer to be 0.68 (95% CI 0.62-0.75). There were no significant differences found between covariates. Heterogeneity among all studies was found to be I=68%.

CONCLUSION

Intrauterine device use is associated with a reduced incidence of ovarian cancer based on a review of existing retrospective data. Unfortunately, prospective investigation into the role of IUDs in ovarian cancer prevention is limited.

Age at menarche and epithelial ovarian cancer risk: A meta-analysis and Mendelian randomization study

Age at menarche (AAM) was found to be associated with ovarian cancer risk in previous observational studies. However, the causality of this association remains unclear. Here, after systematic meta-analyses, we performed two-sample Mendelian randomization (MR) analyses to evaluate the causal effect of AAM in epithelial ovarian cancer (EOC) etiology. We performed meta-analyses including 11 410 cases and 1 163 117 noncases to quantitatively evaluate the association between AAM and ovarian cancer risk. In MR analyses, we used 25 single nucleotide polymorphisms (SNPs) associated with AAM for Chinese and 390 SNPs for Europeans as instrumental variables. MR estimates were calculated using inverse-variance weighted methods from 1044 cases and 1172 controls in a Chinese genome-wide association study and validated by the Ovarian Cancer Association Consortium and Consortium of Investigators of Modifiers of BRCA1/2 studies with 29 396 cases and 68 502 controls of European ancestry. In meta-analyses, we observed an inverse association (odds ratio [OR] = 0.96, 95% confidence interval [CI] = 0.93 to 1.00, P = 0.036) between per year older AAM and ovarian cancer risk in case-control studies, but no association was observed in cohort studies. In MR analyses, the OR of EOC risk per year increase in AAM was 0.81 (95% CI = 0.67 to 0.97, P = 0.026) in Chinese and 0.94 (95% CI = 0.90 to 0.98, P = 0.003) in Europeans, respectively. Our study supports a causal association between AAM and EOC risk.

Association of Combined Estrogen-Progestogen and Progestogen-Only Contraceptives with the Development of Cancer

Combined estrogen-progestogen contraceptives (oral contraceptives or OCs) and progestogen-only contraceptives (POCs) are synthetic steroids that bind to steroid hormone receptors, which are widespread throughout the body. They have a profound effect on cellular physiology. Combined OCs have been classified by the International Agency for Research on Cancer (IARC) as Group 1 carcinogens, but their findings have not been updated recently. In order to update the information and better understand the impact that OCs and POCs have on the risk of development of cancers, a comprehensive literature search was undertaken, focusing on more recently published papers. In agreement with the IARC, the recent literature confirms an increased risk of breast cancer and cervical cancer with the use of OCs. The recent literature also confirms the IARC conclusion that OCs decrease the risk of ovarian and endometrial cancers. However, there is little support from recent studies for the IARC conclusion that OCs decrease the risk of colorectal cancer or increase the risk of liver cancer. For liver cancer, this may be due to the recent studies having been performed in areas where hepatitis is endemic. In one large observational study, POCs also appear to increase the overall risk of developing cancer. OCs and POCs appear to increase the overall risk of cancer when carefully performed studies with the least intrinsic bias are considered.

Summary

OCs have been classified as cancer-causing agents, especially leading to increases in breast cancer and cervical cancer. A review of the recent scientific literature was performed to see whether this still appears to be the case. The recent literature supports the cancer-causing role of OCs especially for breast cancer and cervical cancer. Studies also indicate that progesterone-only contraceptives (such as implants and vaginal rings) also can cause cancer. This is especially true for breast cancer and cervical cancer.

Temporal Trends of Common Female Malignances on Breast, Cervical, and Ovarian Cancer Mortality in Japan, Republic of Korea, and Singapore: Application of the Age-Period-Cohort Model

Background

Reproductive system cancer is an important cause of morbidity and mortality worldwide which threatens women's health and lives. Breast, cervical, and ovarian cancer have the higher incidence and mortality among a series of gynecology malignant tumor. We aimed to compare and assess the temporal trends of common female malignances on breast, cervical, and ovarian cancer mortality in developed regions of Asia including Japan, Republic of Korea, and Singapore and analyze the detached effects of chronological age, time period, and birth cohort by age-period-cohort (APC) analysis.

Methods

The mortality data for these three cancers were collected from the WHO Mortality Database in Japan, Republic of Korea, and Singapore from 1954 to 2013, from 1989 to 2013, and from 1964 to 2013, respectively. We fitted an age-period-cohort model and intrinsic estimator method to estimate the independent effect of each age, time period, and birth cohort on cancer mortality and describe the secular changes in three Asian countries.

Results

For the overall trends of breast cancer, the ASMRs of breast cancer showed a general increasing trend among three countries during the study periods while the change pattern in Singapore was different from the rest of the two countries for cervical and ovarian cancer. By APC analysis, the three cancer mortality risks generally increased with age and decreased with birth cohort. For period effects of breast and ovarian cancer, increasing effects with time were observed; however, for period effects of cervical cancer, converse change pattern was presented among three countries.

Conclusions

Our study shows that the ASMRs of breast, cervical, and ovarian cancer remain high in Singapore compared to Japan and Korea. Generally speaking, the mortality risk of three cancers increased with age, and period and cohort effects may collectively affect the common female malignances mortality for East Asian women.

Breastfeeding and maternal health outcomes: a systematic review and meta-analysis

AIM

To evaluate the effect of breastfeeding on long-term (breast carcinoma, ovarian carcinoma, osteoporosis and type 2 diabetes mellitus) and short-term (lactational amenorrhoea, postpartum depression, postpartum weight change) maternal health outcomes.

METHODS

A systematic literature search was conducted in PubMed, Cochrane Library and CABI databases. Outcome estimates of odds ratios or relative risks or standardised mean differences were pooled. In cases of heterogeneity, subgroup analysis and meta-regression were explored.

RESULTS

Breastfeeding >12 months was associated with reduced risk of breast and ovarian carcinoma by 26% and 37%, respectively. No conclusive evidence of an association between breastfeeding and bone mineral density was found. Breastfeeding was associated with 32% lower risk of type 2 diabetes. Exclusive breastfeeding and predominant breastfeeding were associated with longer duration of amenorrhoea. Shorter duration of breastfeeding was associated with higher risk of postpartum depression. Evidence suggesting an association of breastfeeding with postpartum weight change was lacking.

CONCLUSION

This review supports the hypothesis that breastfeeding is protective against breast and ovarian carcinoma, and exclusive breastfeeding and predominant breastfeeding increase the duration of lactational amenorrhoea. There is evidence that breastfeeding reduces the risk of type 2 diabetes. However, an association between breastfeeding and bone mineral density or maternal depression or postpartum weight change was not evident.

The utility of web mining for epidemiological research: studying the association between parity and cancer risk

BACKGROUND

The World Wide Web has emerged as a powerful data source for epidemiological studies related to infectious disease surveillance. However, its potential for cancer-related epidemiological discoveries is largely unexplored.

METHODS

Using advanced web crawling and tailored information extraction procedures, the authors automatically collected and analyzed the text content of 79 394 online obituary articles published between 1998 and 2014. The collected data included 51 911 cancer (27 330 breast; 9470 lung; 6496 pancreatic; 6342 ovarian; 2273 colon) and 27 483 non-cancer cases. With the derived information, the authors replicated a case-control study design to investigate the association between parity (i.e., childbearing) and cancer risk. Age-adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for each cancer type and compared to those reported in large-scale epidemiological studies.

RESULTS

Parity was found to be associated with a significantly reduced risk of breast cancer (OR = 0.78, 95% CI, 0.75-0.82), pancreatic cancer (OR = 0.78, 95% CI, 0.72-0.83), colon cancer (OR = 0.67, 95% CI, 0.60-0.74), and ovarian cancer (OR = 0.58, 95% CI, 0.54-0.62). Marginal association was found for lung cancer risk (OR = 0.87, 95% CI, 0.81-0.92). The linear trend between increased parity and reduced cancer risk was dramatically more pronounced for breast and ovarian cancer than the other cancers included in the analysis.

CONCLUSION

This large web-mining study on parity and cancer risk produced findings very similar to those reported with traditional observational studies. It may be used as a promising strategy to generate study hypotheses for guiding and prioritizing future epidemiological studies.

Breastfeeding and ovarian cancer risk: a systematic review and meta-analysis of 40 epidemiological studies

The present systematic review and meta-analysis was conducted to assess any association between breastfeeding and the risk of ovarian cancer. A systematic search of published studies was performed in PUBMED and EMBASE and by reviewing reference lists from retrieved articles through March 2013. Data extraction was conducted independently by two authors. Pooled relative risk ratios were calculated using random-effect models. Totals of 5 cohort studies and 35 case-control studies including 17,139 women with ovarian cancer showed a 30% reduced risk of ovarian cancer when comparing the women who had breastfed with those who had never breastfed (pooled RR = 0.70, 95% CI: 0.64-0.76; p = 0.00), with significant heterogeneity in the studies (p = 0.00; I2 = 76.29%). A significant decreasd in risk of epithelial ovarian cancer was also observed (pooled RR = 0.68, 95% CI: 0.61-0.76). When the participants were restricted to only parous women, there was a slightly attenuated but still significant risk reduction of ovarian cancer (pooled RR = 0.76, 95% CI: 0.69-0.83). For total breastfeeding duration, the pooled RRs in the < 6 months, 6-12 months and > 12 months of breastfeeding subgroups were 0.85 (95% CI: 0.77-0.93), 0.73 (95% CI: 0.65-0.82) and 0.64 (95%CI: 0.56-0.73), respectively. Meta-regression of total breastfeeding duration indicated an increasing linear trend of risk reduction of ovarian cancer with the increasing total breastfeeding duration (p = 0.00). Breastfeeding was inversely associated with the risk of ovarian cancer, especially long-term breastfeeding duration that demonstrated a stronger protective effect.

Influence of late-age births on maternal longevity

PURPOSE

To examine the association between the mother's age at last birth and maternal long-term survival.

METHODS

Data from three national censuses (1972, 1983, and 1995) and national birth and death records (1972-2009) were used to examine the association between age at last birth and mortality while accounting for potential confounders, such as parity. Age-adjusted mortality rates and Cox proportional hazard models were used in the analysis.

RESULTS

A total of 887 women who delivered their last child after 45 years of age were identified from among 178,507 women (1,592,379 person-years). Age-adjusted mortality rates from 55 years of age were highest for childless women (9.2 per 1000) and decreased linearly (P < .001) for parous women with increased age at last birth (5.2 per 1000 for women aged ≥45 years at last birth). In models adjusted for age at first birth and parity, mortality risks were lowest among parous women with late-age births (≥45 years) compared with parous women with their last births before 35 years of age (hazard ratio, 0.58; 95% confidence interval, 0.40-0.86).

CONCLUSIONS

This study provides new empirical evidence that late-age births are associated with maternal longevity, although a direct causal relation cannot be established with the information available.

Contraceptive methods and ovarian cancer risk among Chinese women: A report from the Shanghai Women's Health Study

Oral contraceptive use is associated with reduced ovarian cancer risk; however, associations with other contraceptive methods, such as intrauterine device (IUD) and tubal ligation, are less clear. Women in China differ from western women in regard to mechanisms and duration of use of contraception. This study was undertaken to evaluate associations between contraceptive methods and ovarian cancer risk using data from the prospective Shanghai Women's Health Study. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated by Cox proportional hazards regression. A total of 174 epithelial ovarian cancer cases were found to occur among 70,259 women who were followed-up for a total of 888,258 person-years. The majority of women had ever used any contraception (77.0%), including IUD (55.6%), oral contraceptive (20.4%), tubal ligation (14.7%) or contraceptive shots (2.6%). Ever use of any contraception was associated with a nonsignificant reduction in ovarian cancer risk (HR: 0.86, 95% CI: 0.60-1.24). Longer duration of IUD use was associated with lower ovarian cancer risk (p-value for trend = 0.04). Compared with never users, women with durations of IUD use longer than the median (20 years) were 38% less likely to develop ovarian cancer (HR: 0.62, 95% CI: 0.40-0.97). Based on the high prevalence and long duration of IUD use among Chinese women, we estimate a preventive fraction of 9.3%, corresponding to approximately 16 ovarian cancer cases. High prevalence of long-term IUD use may, therefore, contribute to the low incidence of ovarian cancer observed in China.

Reproductive factors for ovarian cancer in southern Chinese women

Objective

To investigate the association between reproductive factors and the risk of ovarian cancer among southern Chinese women.

Methods

A hospital-based case-control study was undertaken in Guangzhou, Guangdong Province, between 2006 and 2008. A structured questionnaire was used to obtain information on parity, oral contraceptive use and other reproductive factors in a sample of 500 incident ovarian cancer patients and 500 controls (mean age, 59 years). Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using unconditional logistic regression models.

Results

High parity was inversely associated with ovarian cancer, with an adjusted OR 0.43 (95% CI, 0.30 to 0.62) for women who had given birth to 3 or more children compared to women who had given no more than one birth. Ever use of oral contraceptives was also protective against ovarian cancer; adjusted OR 0.56 (95% CI, 0.40 to 0.78). No association was found for hormone replacement therapy, menopausal status, hysterectomy and family history of ovarian and/or breast cancer.

Conclusion

High parity and oral contraceptive use are associated with a lower risk of ovarian cancer in southern Chinese women.