Prolonged lactation reduces ovarian cancer risk in Chinese women

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.

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.

Breastfeeding and the risk of ovarian cancer: a meta-analysis

INTRODUCTION

The aim of this meta-analysis was to assess the association between breastfeeding and risk of ovarian cancer.

METHODS

Relevant observational studies were identified by a search of the MEDLINE and EMBASE databases through December 2012. Summary odds ratios (ORs) for ovarian cancer, comparing women who had breastfed with women who had not, were calculated using a random-effects model. A dose-response meta-analysis assessed the risk of ovarian cancer by breastfeeding duration.

RESULTS

A total of 19 studies were included in the meta-analysis. Compared with women who had not breastfed, women who had breastfed had a significantly decreased risk of ovarian cancer, with an OR of 0.66 (95% CI, 0.57-0.76; P < .001). We observed an inverse linear relationship with breastfeeding duration: for every one-month increase in breastfeeding, the OR was 0.98 (95% CI, 0.97-0.99; P < .001). A nonlinear association was also apparent, with a sharp decrease in the OR when breastfeeding duration was 8 to 10 months. There was evidence of heterogeneity (I(2)  = 83.9%). No publication bias was found (Begg test, P = 0.89; Egger test, P = 0.89).

DISCUSSION

Breastfeeding reduces the risk of ovarian cancer proportional to duration. Breastfeeding for 8 to 10 months may be most effective for reducing the risk of ovarian cancer.

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.

Use of fertility drugs and risk of ovarian cancer

PURPOSE OF REVIEW

The purpose of this review is to highlight recent research and insights into the relationship between fertility drug use and ovarian cancer risk.

RECENT FINDINGS

Results from two large case-control studies provided further evidence that fertility drug use does not significantly contribute to risk of ovarian cancer among the majority of women when adjusting for known confounding factors. However, questions regarding the effect on certain subgroups, including long-term fertility drug users, women who remain nulligravid after fertility treatment, women with BRCA1 or BRCA2 mutations and borderline ovarian tumours, still remain. In addition, it may currently just be too early to determine whether there is an association between fertility drug use and ovarian cancer risk given that many of the exposed women are only now beginning to reach the ovarian cancer age range.

SUMMARY

Whether use of fertility drugs increases the risk of ovarian cancer is an important question that requires further investigation, in particular given the large number of women utilizing fertility treatments. Fortunately, results from recent studies have been mainly reassuring. Large well designed studies with sufficient follow-up time are needed to further evaluate the effects of fertility treatments within subgroups defined by patient and tumour characteristics.

Breastfeeding and ovarian cancer risk: a meta-analysis of epidemiologic studies

BACKGROUND

Epidemiologic studies have yielded inconsistent findings between breastfeeding and epithelial ovarian cancer (EOC) risk.

OBJECTIVE

We performed a meta-analysis to summarize available evidence of the association between breastfeeding and breastfeeding duration and EOC risk from published cohort and case-control studies.

DESIGN

Relevant published studies were identified by a search of MEDLINE through December 2012. Two authors (T-TG and Q-JW) independently performed the eligibility evaluation and data abstraction. Study-specific RRs from individual studies were pooled by using a random-effects model, and heterogeneity and publication-bias analyses were conducted.

RESULTS

Five prospective and 30 case-control studies were included in this analysis. The pooled RR for ever compared with never breastfeeding was 0.76 (95% CI: 0.69, 0.83), with moderate heterogeneity (Q = 69.4, P < 0.001, I(2) = 55.3%). Risk of EOC decreased by 8% for every 5-mo increase in the duration of breastfeeding (RR: 0.92; 95% CI: 0.90, 0.95). The risk reduction was similar for borderline and invasive EOC and was consistent within case-control and cohort studies.

CONCLUSIONS

Results of this meta-analysis support the hypothesis that ever breastfeeding and a longer duration of breastfeeding are associated with lower risks of EOC. Additional research is warranted to focus on the association with cancer grade and histologic subtypes of EOC.

Korean epithelial ovarian cancer study (Ko-EVE): protocols and interim report

BACKGROUND

There have been few studies of Asian ovarian cancer and benign tumors. The primary aim of this paper was to report the protocol of the Ko-EVE study to examine epidemiological and molecular factors for ovarian cancer and benign neoplasms and to ascertain the major risk factors for ovarian cancer control in Korea.

METHODS

This case-control study covers incident epithelial ovarian cancers and benign neoplasms, four major centers participating in enrolling incident cases and 3 hospitals enrolling healthy controls among health examinees. Standardized questionnaires were administered by trained interviewers, including sections on socio-demographics characteristics, past medical history, medication usage, family history, lifetime consumption of alcohol and tobacco, diet, physical activity, and reproductive factors for women. Various biological specimens were collected in the biorepository according to the standardized protocol. Annual follow-up for cancer cases and follow-up at the 1st year for benign tumor cases are performing to evaluate treatment effect and progression. Passive follow to see long-term survival will be conducting using record linkage with national data.

RESULTS

The total number recruited in 2010-2011 was 246 epithelial ovarian cancer cases, 362 benign epithelial tumors and 345 controls. We are planning to collect subjects for at least 1,500 sets of ovarian cancer, 2,000 benign tumors and 1,500 controls till 2018.

CONCLUSION

The Ko-EVE will provide unique and important data to probe the etiology and natural history of Korean epithelial ovarian cancer. It will be continued by genomic and proteomic epidemiological analyses and future intervention studies for the prevention of ovarian cancer among Koreans.

Ovarian cancer risk is reduced by prolonged lactation: a case-control study in southern China

BACKGROUND

Ovarian cancer is an important neoplasm that is difficult to diagnose and treat; therefore, prevention is the preferable strategy. Growing evidence indicates a protective effect of breastfeeding on ovarian cancer risk.

OBJECTIVE

The objective was to investigate the association between lactation and the risk of ovarian cancer among southern Chinese women.

DESIGN

A case-control study was undertaken in Guangzhou, Guangdong Province, between August 2006 and July 2008. A validated and reliable questionnaire was used to obtain information on the months of lactation and number of children breastfed in a sample of 493 incident ovarian cancer patients and 472 hospital-based controls (mean age: 59 y). Logistic regression analyses were performed to assess the association between breastfeeding and the risk of ovarian cancer.

RESULTS

Significant inverse dose-response relations were found for both duration of lactation and the number of children breastfed. The adjusted ORs were 0.09 (95% CI: 0.04, 0.19) for women with ≥31 mo of total lactation and those with ≤10 mo of lactation and 0.38 (95% CI: 0.27, 0.55) for women with ≥3 children breastfed compared with those with one child breastfed.

CONCLUSION

Prolonged lactation is associated with a lower risk of ovarian cancer in parous Chinese women.

Use of fertility drugs and risk of ovarian cancer: results from a U.S.-based case-control study

BACKGROUND

Previous studies examining associations between use of fertility drugs and ovarian cancer risk have provided conflicting results. We used data from a large case-control study to determine whether fertility drug use significantly impacts ovarian cancer risk when taking into account parity, gravidity, and cause of infertility.

METHODS

Data from the Hormones and Ovarian Cancer Prediction (HOPE) study were used (902 cases, 1,802 controls). Medical and reproductive histories were collected via in-person interviews. Logistic regression was used to calculate ORs and 95% confidence intervals (CI). Models were adjusted for age, race, education, age at menarche, parity, oral contraceptive use, breastfeeding, talc use, tubal ligation, and family history of breast/ovarian cancer.

RESULTS

Ever use of fertility drugs was not significantly associated with ovarian cancer within the total HOPE population (OR, 0.93; 95% CI, 0.65-1.35) or among women who reported seeking medical attention for infertility (OR, 0.87; 95% CI, 0.54-1.40). We did observe a statistically significant increased risk of ovarian cancer for ever use of fertility drugs among women who, despite seeking medical attention for problems getting pregnant, remained nulligravid (OR, 3.13; 95% CI, 1.01-9.67).

CONCLUSIONS

These results provide further evidence that fertility drug use does not significantly contribute to ovarian cancer risk among the majority of women; however, women who despite infertility evaluation and fertility drug use remain nulligravid, may have an elevated risk for ovarian cancer.

IMPACT

Our results suggest that fertility drug use does not significantly contribute to overall risk of ovarian cancer when adjusting for known confounding factors.

Breast-feeding and risk of epithelial ovarian cancer

PURPOSE

Evidence suggests that breast-feeding may decrease the risk of epithelial ovarian cancer but it is not clear whether there is a relationship with duration of breast-feeding, patterns of breast-feeding, or particular histological subtypes of ovarian cancer. We sought to investigate these issues in detail.

METHODS

Data from participants in a population-based study of ovarian cancer in western Washington State, USA (2002-2007) who had had at least one birth (881 cases and 1,345 controls) were used to assess relations between patterns of breast-feeding and ovarian cancer. Logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Women who ever breast-fed had a 22 % reduction in risk of ovarian cancer compared with those who never breast-fed (OR = 0.78, 95% CI 0.64-0.96) and risk reduction appeared greater with longer durations of feeding per child breast-fed (OR = 0.56, 95% CI 0.32-0.98 for 18 months average duration breast-feeding versus none). Introduction of supplementary feeds did not substantially alter these effects. The overall risk reduction appeared greatest for the endometrioid and clear cell subtypes (OR per month of average breast-feeding per child breast-fed = 0.944, 95% CI 0.903-0.987).

CONCLUSIONS

Among women who have had the opportunity to breast-feed, ever breast-feeding and increasing durations of episodes of breast-feeding for each breast-fed child are associated with a decrease in the risk of ovarian cancer independent of numbers of births, which may be strongest for the endometrioid subtype.

Dads make a difference: an exploratory study of paternal support for breastfeeding in Perth, Western Australia

BACKGROUND

The ability to breastfeed and continue the practice requires dedication, commitment, persistence and support. Mothers often need to overcome many obstacles to successfully breastfeed their babies and maintain their balance of home, family and work commitments. Evidence suggests that fathers want to be involved and be part of the parenthood process, including infant feeding. The role transition from couple to family poses challenges to both parents. Sharing the experience of childbirth and supporting each other in the subsequent infant feeding practices is one of those challenges.

METHODS

A qualitative exploratory design was chosen to identify parents' perceptions of what constitutes support for breastfeeding, particularly focusing upon paternal support. Focus groups were conducted with mothers and a focus group, interviews and an online survey were developed for fathers. Thematic analysis was used to identify the main themes.

RESULTS

From a total of 76 participants, the major theme emerging from mothers' data identified that "Dads do make a difference". Three sub-themes included: Anticipating needs and getting the job done; Encouragement to do your best; and Paternal determination and commitment, associated with effective partner support. "Wanting to be involved" was identified from fathers' data as the major theme around their needs. Three sub-themes included: Wanting more information; Learning the role; and Being an advocate.

CONCLUSION

Sharing the experience of childbirth and supporting each other in the subsequent infant feeding practices was perceived as the best outcome for the majority of new mothers and fathers. Paternal emotional, practical and physical supports were identified as important factors to promote successful breastfeeding and to enrich the experience for the mother and subsequently the father. TRAIL REGRISTRATION: Australia and New Zealand Clinical Trials Registry: ACTRN12609000667213.

Breast-feeding the last born child and risk of ovarian cancer

Conflicting reports regarding the relationship between breast-feeding and ovarian cancer risk suggest a possible influence of patterns of breast-feeding. We used logistic regression to examine breast-feeding in a large population of parous women who participated in a case-control study of ovarian cancer in New Hampshire and MA, USA. Risk of ovarian cancer was reduced in parous women who ever breast-fed (OR: 0.75; 95% CI: 0.62, 0.92), but evidence was limited for an influence of duration of breast-feeding and the number of children breast-fed. Compared to never breast-feeding, inverse associations were seen for breast-feeding all children (OR: 0.72; 95% CI: 0.58, 0.91) and for breast-feeding some children when the last born child was breast-fed (OR: 0.58; 95% CI: 0.37, 0.91). There was little evidence of reduced risk for those who breast-fed some children when the last born child was not breast-fed (OR: 0.91; 95% CI: 0.66, 1.26). Similar findings were noted in women with exactly two children and in those with two or more children. The protective influence of breast-feeding on ovarian cancer risk may be limited to women who breast-feed their last born child. These findings, which require confirmation by future studies, imply that breast-feeding resets pregnancy-related states that mediate ovarian cancer risk.

Breastfeeding and the risk of epithelial ovarian cancer in an Italian population

OBJECTIVES

Breastfeeding has been inversely related to the risk of ovarian cancer, but results from published studies are inconsistent. In order to provide further information, we analyzed data from a large case-control study conducted in four Italian areas.

METHODS

Cases were 1031 women with epithelial ovarian cancer. Controls were 2411 women admitted to the same network of hospitals for a wide spectrum of acute non-neoplastic conditions, unrelated to known risk factors for ovarian cancer.

RESULTS

There were inverse trends in risk with increasing duration of breastfeeding and number of children breastfed, but when parity and several other potential confounding factors were taken into account, no residual association was evident (odds ratio = 1.21 for 17 or more months of breastfeeding and 0.90 for those who had breastfed 4 or more children, as compared to women who had never breastfed).

CONCLUSIONS

This study showed an inverse relation between breastfeeding and ovarian cancer risk, which however was accounted for by parity. The analyses by histologic subtypes suggested that a role of breastfeeding would be larger for serous neoplasms in the absence, however, of significant heterogeneity.