Menstrual and reproductive factors in women, genetic variation in CYP17A1, and pancreatic cancer risk in the European prospective investigation into cancer and nutrition (EPIC) cohort

Association of Menopausal Hormone Therapy with Risk of Pancreatic Cancer: A Systematic Review and Meta-analysis of Cohort Studies

BACKGROUND

Although menopausal hormone therapy (MHT) is commonly prescribed, little is known about the association between MHT use and risk of pancreatic cancer.

METHODS

We searched PubMed, Embase, and Cochrane Library, from inception until April 20, 2022. The risk of bias was assessed with the Newcastle-Ottawa Quality Assessment Scale. Pooled relative risks (RR) for pancreatic cancer risk were calculated using random-effects models. We computed prediction intervals (PI) and performed subgroup meta-analyses. Meta-regression was performed to investigate the sources of heterogeneity.

RESULTS

This study included 2,712,313 women from 11 cohort studies. There was no association between MHT and pancreatic cancer risk (RR, 0.92; 95% confidence interval (CI), 0.83-1.02; I2, 64%; 95% PI, 0.68-1.25). Subgroup meta-analyses of four studies stratified by MHT formulations showed inverse associations with the risk of pancreatic cancer (women receiving estrogen-only MHT: RR, 0.77; 95% CI, 0.64-0.94; I2, 57%; estrogen plus progestin MHT: RR, 0.85; 95% CI, 0.75-0.96; I2, 0%). Subgroup analysis defined by recency and duration of treatment did not reveal evidence of associations between MHT and pancreatic cancer risk.

CONCLUSIONS

This study found no association between the overall use of MHT and risk of pancreatic cancer. However, among four studies with data on MHT formulations, subgroup analysis showed a decreased risk of pancreatic cancer among users of estrogen-only and combined estrogen-progestin therapy. Owing to the inconsistent findings between our main and subgroup analyses, future studies stratified by MHT formulations are warranted.

IMPACT

The findings of this study indicate that future investigation should focus on MHT formulations.

Use of oral contraceptives and risk of pancreatic cancer in women: A recalculated meta-analysis of prospective cohort studies

In a recent systematic review and meta-analysis of observational studies, the author found potential errors in the selection and extraction processes. The recalculated summary relative risks and the results of a dose-response meta-analysis showed that oral contraceptive use may not be associated with the risk of pancreatic cancer in women.

Association between oral contraceptive use and pancreatic cancer risk: A systematic review and meta-analysis

BACKGROUND

Studies on the association of oral contraceptive (OC) use and pancreatic cancer showed inconsistent findings.

AIM

To evaluate the relationship between OC use and pancreatic cancer risk.

METHODS

A literature search for observational studies (case-control and cohort studies) was conducted up to December 2020. A meta-analysis was performed by calculating pooled relative risks (RRs) and 95% confidence intervals (CIs). Heterogeneity was assessed using Cochran’s chi-square test and I² statistic. Subgroup analyses were performed by study design, source of controls in case-control studies, number of cases of pancreatic cancers, study quality according to Newcastle-Ottawa Scale score, geographical region and menopausal status. All analyses were performed using Review Manager 5.3 (RevMan 5.3).

RESULTS

A total of 21 studies (10 case-control studies and 11 cohort studies) were finally included in the present meta-analysis, comprising 7700 cases of pancreatic cancer in total. A significant association was observed between the ever use of OC and pancreatic cancer risk in the overall analysis (RR = 0.85; 95%CI = 0.73-0.98; P = 0.03). Duration of OC use (< 1 year, < 5 years, 5-10 years, > 10 years) was not significantly associated with the risk of pancreatic cancer. Subgroup analyses revealed a statistically significant subgroup difference for the geographic region in which the study was conducted (Europe vs Americas vs Asia; P = 0.07). Subgroup analyses showed a statistically significant decrease in pancreatic cancer risk and OC use in high-quality studies, studies conducted in Europe, and in postmenopausal women.

CONCLUSION

Despite the suggested protective effects of OC use in this meta-analysis, further epidemiological studies are warranted to fully elucidate the association between the use of OC and pancreatic cancer risk.

Reproductive Factors, Use of Exogenous Hormones, and Pancreatic Cancer Incidence: The Norwegian Women and Cancer Study

Introduction

The incidence of pancreatic cancer is increasing worldwide and characterized by a particularly low survival rate. Studies have reported weak and inconsistent evidence for associations among reproductive factors, use of exogenous hormones, and pancreatic cancer incidence in women.

Purpose

To investigate relationships between reproductive factors, exogenous hormones, and the rate of pancreatic cancer incidence in a large population-based prospective cohort of women in Norway.

Methods

We used data from the Norwegian Women and Cancer study on 588 incident cases of pancreatic cancer diagnosed among 165,419 women, with mean follow-up of 18.7 years. Cox proportional-hazard models were used to estimate HRs and 95% CIs for associations of interest.

Results

Cumulative breastfeeding duration >24 months was associated with 63% decreased incidence of pancreatic cancer compared to no breastfeeding. We observed an inverse linear dose–response trend between cumulative breastfeeding duration and pancreatic cancer incidence, which was confirmed in parous women and ever-smokers. Higher age at first birth and menopause were inversely associated with pancreatic cancer incidence, though with less precise effect estimates. Current use of oral contraceptives was associated with a doubling of pancreatic cancer incidence, but the analysis was hampered by a small number of cases. There was no evidence of any associations between age at menarche, parity or use of menopausal hormone therapy, and incidence of pancreatic cancer.

Conclusion

Our results suggest a potential protective effect of breastfeeding duration against pancreatic cancer incidence. Inconsistent results for the other reproductive factors suggested no important role of estrogens in pancreatic cancer etiology.

Effects of lentivirus-mediated CYP17A1 gene silencing on the biological activity of glioma

Gliomas are the most common malignant primary brain tumors with poor prognosis. We attempted to explore the role of CYP17A1 in glioma progression. We demonstrated that the expression of CYP17A1 was significantly higher in the glioma tissues than the normal brain tissues, especially in malignant glioma. Moreover, the expression of CYP17A1 gene was positively correlative with glioma pathological grades. In vitro, CYP17A1 gene silence inhibited the proliferation and invasion of glioma cells and promoted the apoptosis in glioma cells. Also, the subcutaneously transplanted tumour in BALB/C-nu showed that CYP17A1 gene silence inhibited glioma growth. These results reveal that CYP17A1 plays a major role in the progress of glioma.

Hormonal contraceptive use and risk of pancreatic cancer-A cohort study among premenopausal women

IMPORTANCE

The association between the use of hormonal contraceptive and pancreatic cancer among premenopausal women has until now been unclear. This is the first study to investigate the risk of pancreatic cancer in pre-menopausal women.

OBJECTIVE

To determine whether hormonal contraception increases the risk of developing pancreatic cancer in pre-menopausal women.

DESIGN

A nationwide prospective cohort study followed all women in Denmark in the age range of 15-49 years without previous cancer or venous thrombosis from 1995 to 2014. The Danish National Prescription Registry provided individually updated exposure information on use of hormonal contraception. The Danish Cancer Registry provided cancer diagnoses, and the Danish National Patient Register containing clinical diagnoses and surgical codes at discharge from public and private hospitals.

SETTING

Population-based cohort study.

PARTICIPANTS

All women living in Denmark aged 15-49 years at January 1st, 1995, and those subsequently reaching age 15 years up to December 31st, 2014 were eligible for the study.

RESULTS

Among 1.9 million women who were followed on average for 11.4 years, 235 pancreatic cancers occurred. Compared to never users, ever users of any type of hormonal contraception had a relative risk (RR) of pancreatic cancer of 0.90 (95% confidence interval (CI) 0.68-1.19). No overall association between duration of hormonal contraceptive use and pancreatic cancer risk was found. Neither was long-term use of hormonal contraception associated with pancreas cancer, RR 0.83 (95% CI 0.47-1.50). The risk did not vary between users of combined and progestogen-only products. All models were adjusted for age, completed or ongoing education, polycystic ovary syndrome, endometriosis and among parous women; parity, age at first birth, smoking and body mass index.

CONCLUSIONS AND RELEVANCE

Compared to never users the risk of pancreatic cancer is not significantly higher among current and recent users of contemporary hormonal contraception and does not vary between users of combined and progestogen-only products. In conclusion, our study suggests no risk of pancreatic cancer with use of any type of hormonal contraception.

Oral Contraceptive Use and Risks of Cancer in the NIH-AARP Diet and Health Study

Although use of oral contraceptives (OCs) is common, their influence on carcinogenesis is not fully understood. We used Cox proportional hazards models to examine OC use (never/<1 year (referent), 1-4, 5-9, ≥10 years) and development of incident cancers across body sites within the same base population: women in the prospective National Institutes of Health-AARP Diet and Health Study (enrolled 1995-1996 and followed until 2011). Adjustment for confounding varied by outcome; all models accounted for age, race, body mass index, and smoking status, and included at least 100,000 women. Any OC use conferred a 3% reduction in the risk for any cancer (hazard ratio = 0.97, 95% confidence interval: 0.95, 0.99). Expected risk reductions that strengthened with duration of use were identified for ovarian and endometrial cancers and were suggested for kidney cancer (all P for trend < 0.05). Non-Hodgkin lymphoma risk (hazard ratio = 0.79, 95% confidence interval: 0.64, 0.97) was reduced with 10 or more years of OC use. There was a 37% reduced risk for bladder cancer and 46% increased risk for pancreatic cancer among long-term OC users who were 60 years of age or younger at baseline. OC use did not influence risks for most other cancers evaluated. Given the high prevalence of use and changing formulations, additional studies are warranted to fully understand the chemopreventive effects of these medications.

Hormonal factors and pancreatic cancer risk in women: The Malmö Diet and Cancer Study

The incidence of pancreatic cancer is leveling between sexes. Smoking, high age and heredity are established risk factors, but evidence regarding the influence of hormonal factors is unclear. In this study, we investigated the associations of reproductive factors, use of oral contraceptives (OC) and hormone replacement therapy (HRT) with pancreatic cancer risk in the Malmö Diet and Cancer Study, a prospective, population‐based cohort encompassing 17,035 women. Up until 31 December 2015, 110 women were identified with incident pancreatic cancer through the Swedish Cancer Registry. Higher age at menarche was significantly associated with pancreatic cancer risk (age‐adjusted [hazard ratio] HR = 1.17; 95% confidence interval [CI] 1.04–1.32, and fully adjusted HR = 1.17; 95% CI 1.04–1.32). Ever use of OC was not significantly associated with pancreatic cancer risk but ever use of HRT was significantly associated with a decreased risk of pancreatic cancer (age‐adjusted HR = 0.47, 95% CI 0.23–0.97, and fully adjusted HR = 0.48, 95% CI 0.23–1.00), in particular use of estrogen‐only regimen (age‐adjusted HR = 0.21; 95% CI 0.05–0.87 and fully adjusted HR = 0.22; 95% CI 0.05–0.90). Age at menopause or first childbirth, parity and breastfeeding history were not significantly associated with pancreatic cancer risk. Collectively, these findings suggest a protective role of female hormones against pancreatic cancer. Further studies are needed, and potential modifying genetic factors and indirect hazardous effects of smoking should also be considered.

What's new?

Female hormones appear to protect against pancreatic cancer, at least in Sweden. Numerous studies have investigated the relationship between the two, but no clear picture has yet emerged. These authors used data from the Malmö Diet and Cancer study, looking for correlations between hormone levels and cancer risk. They found that a younger start to menstruation—indicating an earlier boost in estrogen—correlated with less chance of developing pancreatic cancer. Use of hormone replacement therapy, particularly estrogen‐only therapy, significantly reduced risk among postmenopausal women. Breastfeeding, oral contraceptive use and parity did not appear to affect pancreatic cancer risk.

Reproductive factors, exogenous hormone use, and risk of pancreatic cancer in postmenopausal women

INTRODUCTION

The epidemiologic literature on menstrual and reproductive factors associated with pancreatic cancer has yielded weak and inconsistent evidence of an association. Furthermore, few cohort studies have examined the association of exogenous hormone use, including type and duration, with this disease. The aim of this study was to assess the association of these exposures with risk of pancreatic cancer in a large cohort of postmenopausal women.

METHODS

We used data from the Women's Health Initiative on 1003 cases of pancreatic cancer diagnosed among 158,298 participants over 14.3 years of follow-up. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) for the associations of interest.

RESULTS

Being parous vs. nulliparous was associated with reduced risk (HR=0.84, 95% CI 0.70-1.00), and women who had 1-2 and 3-4 births were at decreased risk compared to nulliparous women, whereas women who had >5 births showed no decrease in risk. Compared to women who gave birth between the ages of 20-29, women who gave birth at age 30 or above were at increased risk (HR 1.23, 95% CI 1.00-1.53, p for trend 0.003). Other reproductive factors and exogenous hormone use were not associated with risk.

CONCLUSIONS

Together with the existing literature on this topic, our results suggest that reproductive and hormonal exposures are unlikely to play an important role in the etiology of pancreatic cancer.

Common variation of the CYP17 gene in Iraqi women with endometriosis disease

Common variants among genes coding for enzymes in sex steroid biosynthetic pathways may influence the risk of endometriosis in Iraqi women patients in the last years. Cytochrome P450c17a1 (CYP17), a gene that codes for a key enzyme (cytochrome P450c17a1) in a rate-limiting step of estrogen biosynthesis has attracted considerable attention as an important gene for endometriosis. To evaluate the relationship between common genetic variations in CYP17 and endometriosis risk and determine the main effects of those variations on the gene expression. A women-based case control study of Iraqi women aged range (23–46), the associations between selected single-nucleotide polymorphisms (SNPs) in the CYP17 gene and endometriosis diagnosis in fifty women and thirty disease-free controls were evaluated. The study found a significant association (P ≤ 0.01)between endometriosis and selected SNPs of CYP17 gene, with the homozygous genotype conferring decreased risk. A highly significant difference (P ≤ 0.01) in CYP17 gene expression from women with versus without endometriosis and increased by 1.56-fold in women with endometriosis. These findings suggest that variation in or around CYP17 may be associated with endometriosis development in the Iraqi women.

Analysis of Important Gene Ontology Terms and Biological Pathways Related to Pancreatic Cancer

Pancreatic cancer is a serious disease that results in more than thirty thousand deaths around the world per year. To design effective treatments, many investigators have devoted themselves to the study of biological processes and mechanisms underlying this disease. However, it is far from complete. In this study, we tried to extract important gene ontology (GO) terms and KEGG pathways for pancreatic cancer by adopting some existing computational methods. Genes that have been validated to be related to pancreatic cancer and have not been validated were represented by features derived from GO terms and KEGG pathways using the enrichment theory. A popular feature selection method, minimum redundancy maximum relevance, was employed to analyze these features and extract important GO terms and KEGG pathways. An extensive analysis of the obtained GO terms and KEGG pathways was provided to confirm the correlations between them and pancreatic cancer.

Menstrual and Reproductive Factors, Hormone Use, and Risk of Pancreatic Cancer: Analysis From the International Pancreatic Cancer Case-Control Consortium (PanC4)

OBJECTIVES

We aimed to evaluate the relation between menstrual and reproductive factors, exogenous hormones, and risk of pancreatic cancer (PC).

METHODS

Eleven case-control studies within the International Pancreatic Cancer Case-control Consortium took part in the present study, including in total 2838 case and 4748 control women. Pooled estimates of odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated using a 2-step logistic regression model and adjusting for relevant covariates.

RESULTS

An inverse OR was observed in women who reported having had hysterectomy (ORyesvs.no, 0.78; 95% CI, 0.67-0.91), remaining significant in postmenopausal women and never-smoking women, adjusted for potential PC confounders. A mutually adjusted model with the joint effect for hormone replacement therapy (HRT) and hysterectomy showed significant inverse associations with PC in women who reported having had hysterectomy with HRT use (OR, 0.64; 95% CI, 0.48-0.84).

CONCLUSIONS

Our large pooled analysis suggests that women who have had a hysterectomy may have reduced risk of PC. However, we cannot rule out that the reduced risk could be due to factors or indications for having had a hysterectomy. Further investigation of risk according to HRT use and reason for hysterectomy may be necessary.

Environmental risk factors for pancreatic cancer: an update

Pancreatic cancer (PC) is one of the most aggressive diseases. Only 10 % of all PC cases are thought to be due to genetic factors. Here, we analyzed the most recently published case-control association studies, meta-analyses, and cohort studies with the aim to summarize the main environmental factors that could have a role in PC. Among the most dangerous agents involved in the initiation phase, there are the inhalation of cigarette smoke, and the exposure to mutagenic nitrosamines, organ-chlorinated compounds, heavy metals, and ionizing radiations. Moreover, pancreatitis, high doses of alcohol drinking, the body microbial infections, obesity, diabetes, gallstones and/or cholecystectomy, and the accumulation of asbestos fibers seem to play a crucial role in the progression of the disease. However, some of these agents act both as initiators and promoters in pancreatic acinar cells. Protective agents include dietary flavonoids, marine omega-3, vitamin D, fruit, vegetables, and the habit of regular physical activity. The identification of the factors involved in PC initiation and progression could be of help in establishing novel therapeutic approaches by targeting the molecular signaling pathways responsive to these stimuli. Moreover, the identification of these factors could facilitate the development of strategies for an early diagnosis or measures of risk reduction for high-risk people.

Correlation between reproductive factors and pancreatic cancer in northwest China

AIM: To assess the correlation between reproductive factors and pancreatic cancer in Chinese female Hans from northwest China, in order to find a new strategy for the prevention and treatment of pancreatic cancer.

METHODS: A total of 154 female pancreatic cancer patients treated at the Second Affiliated Hospital of Xi'an Jiaotong University from 2008 to 2014 were included in a case group, and 251 gender and age matched hospitalized patients without gynecological and endocrine disease were included in a control group. A case-control study was carried out, and odds ratio (OR) and its 95% confidence interval (95%CI) estimating the relative risk of each factor (including parity, age at menarche and age at menopause) to pancreatic cancer were calculated to assess their correlation.

RESULTS: In the female Han population, compared with the hospitalized patients without gynecological and endocrine disease, multiple births (≥3) was a risk factor for pancreatic cancer (OR = 2.42, 95%CI: 1.43-4.10). In univariate analysis, compared with non-menopausal women, menopausal woman had a higher risk to develop pancreatic cancer (OR = 4.65), and menarche at age less than or equal to 14 years was associated with a lower risk to develop pancreatic cancer. In multivariate analysis, age at menarche and age at menopause were not associated with the incidence of pancreatic cancer. When distribution characteristics of parity in patients with pancreatic cancer were studied, compared with the control group of patients, patients with pancreatic cancer had a significantly higher proportion of multiple births (≥3) compared with the control group (P < 0.05).

CONCLUSION: In the female Han population, multiple births may be a risk factor for pancreatic cancer. Age at menarche and age at menopause are not significantly associated with the incidence of pancreatic cancer. Compared with hospitalized patients without gynecological and endocrine disease, patients with pancreatic cancer have a higher proportion of multiple births.

Older age at first birth is a risk factor for pancreatic cancer: a meta-analysis

BACKGROUND

Some studies found that age at first birth is associated with pancreatic cancer; others did not. The present meta-analysis was to evaluate the relationship between age at first birth and pancreatic cancer in women.

DATA SOURCES

We searched PubMed, Embase, and the Cochrane Library for relevant publications on age at first birth and pancreatic cancer up to April, 2014. The eligible studies (six cohorts and five case-controls) were independently selected by two authors. Pooled relative risk (RR) estimates and corresponding 95% confidence interval (95% CI) were calculated using the inverse-variance method.

RESULTS

The pooled RR of pancreatic cancer risk for the highest versus lowest categories of age at first birth was 1.21 (95% CI: 1.01-1.45, P=0.314, I2=13.7%). Consistent relationships were also observed within subgroup analyses stratified by study design, geographic region, and whether the studies included adjustment for cigarette smoking, diabetes, or all of the confounders. In this meta-analysis, no publication bias among studies was observed using Egger's test (P=0.383) or Begg's test (P=0.436).

CONCLUSION

Our findings suggest that older age at first birth is associated with an increased risk of pancreatic cancer in women and the exact functional mechanism needs further investigation.

Relationship between female hormonal and menstrual factors and pancreatic cancer: a meta-analysis of observational studies

The objective of this study was to assess the relationship between female hormone and menstrual factors and pancreatic cancer (PC) through a meta-analysis of observational studies. We undertook a systematic literature search up to July 10, 2014 in PubMed and EMBASE databases. Combined relative risks (RRs) were estimated by random-effects models. Subgroup analysis was performed by study design, source of control, and geographic regions. Sensitivity analyses and publication bias were utilized to evaluate the robustness of our results. A total of 27 case-control and cohort studies were retrieved for this meta-analysis. No significant associations were observed between the risk of PC and age at menarche (RR = 0.94, 95% confidence interval [CI] 0.83-1.07), age at menopause (RR = 0.98, 95% CI 0.85-1.13), hysterectomy (RR = 0.97, 95% CI 0.84-1.11), oophorectomy (RR = 1.02, 95% CI 0.82-1.26), hormone replacement therapy (RR = 0.97, 95% CI 0.87-1.08), and oral contraceptives (RR = 1.09, 95% CI 0.96-1.23). This meta-analysis of observational studies does not support the hypothesis that exogenous hormone use and menstrual factors are associated with PC.

Serum CA19-9 is significantly upregulated up to 2 years before diagnosis with pancreatic cancer: implications for early disease detection

PURPOSE

Biomarkers for the early detection of pancreatic cancer are urgently needed. The primary objective of this study was to evaluate whether increased levels of serum CA19-9, CA125, CEACAM1, and REG3A are present before clinical presentation of pancreatic cancer and to assess the performance of combined markers for early detection and prognosis.

EXPERIMENTAL DESIGN

This nested case-control study within the UKCTOCS included 118 single and 143 serial serum samples from 154 postmenopausal women who were subsequently diagnosed with pancreatic cancer and 304 matched noncancer controls. Samples were split randomly into independent training and test sets. CA19-9, CA125, CEACAM1, and REG3A were measured using ELISA and/or CLIA. Performance of markers to detect cancers at different times before diagnosis and for prognosis was evaluated.

RESULTS

At 95% specificity, CA19-9 (>37 U/mL) had a sensitivity of 68% up to 1 year, and 53% up to 2 years before diagnosis. Combining CA19-9 and CA125 improved sensitivity as CA125 was elevated (>30 U/mL) in approximately 20% of CA19-9-negative cases. CEACAM1 and REG3A were late markers adding little in combined models. Average lead times of 20 to 23 months were estimated for test-positive cases. Prediagnostic levels of CA19-9 and CA125 were associated with poor overall survival (HR, 2.69 and 3.15, respectively).

CONCLUSIONS

CA19-9 and CA125 have encouraging sensitivity for detecting preclinical pancreatic cancer, and both markers can be used as prognostic tools. This work challenges the prevailing view that CA19-9 is upregulated late in the course of pancreatic cancer development.

Parity and pancreatic cancer risk: evidence from a meta-analysis of twenty epidemiologic studies

Multiple studies have hypothesized parity is associated with pancreatic cancer risk but obtained conflicting results. We conducted a meta-analysis (including a dose-response approach) of current available epidemiologic studies to investigate the association between parity and risk of pancreatic cancer. Ten cohort studies and ten case-control studies including 8205 cases were eligible for inclusion. The combined RR (relative risk) of pancreatic cancer for the parous vs. nulliparous was 0.91 (95% CI, confidence interval = 0.85–0.97, I² = 39.0%, P_h = 0.01). We observed an inverse association between giving birth to two children pancreatic cancer risk with RR of 0.86 (95% CI = 0.80–0.93, I² = 8.7%, P_h = 0.36). And no evidence supported there was non-linear (P = 0.33) or linear relationship (P = 0.14) between number of parity and risk of pancreatic cancer. Findings from this meta-analysis indicate that giving birth to two children has the lowest pancreatic cancer risk, mechanism of this protective effect needs further investigation.

Parity and pancreatic cancer risk: a dose-response meta-analysis of epidemiologic studies

Background

Previous epidemiologic studies have reported inconsistent results between parity and pancreatic cancer (PC) risk. To our knowledge, a comprehensive and quantitative assessment of this association has not been conducted.

Methods

Relevant published studies of parity and PC were identified using MEDLINE (PubMed) and Web of Science databases until November 2013. Two authors (H-BG and LW) independently assessed eligibility and extracted data. Eleven prospective and 11 case-control studies reported relative risk (RR) estimates and 95% confidence intervals (CIs) of PC associated with parity. Fixed- and random-effects models were used to estimate the summary RR depending on the heterogeneity of effects.

Results

The summary RR for PC comparing the highest versus lowest parity was 0.86 (95% CI: 0.73–1.02; Q = 50.49, P<0.001, I² = 58.4%). Significant inverse associations were also observed in the studies that adjusted for cigarette smoking (RR = 0.81; 95% CI: 0.68–0.98), Type 2 diabetes mellitus (RR = 0.83; 95% CI: 0.75–0.93), and those that included all confounders or important risk factors (RR = 0.85; 95% CI: 0.76–0.96). Additionally, in the dose-response analysis, the summary RR for per one live birth was 0.97 (95% CI: 0.94–1.01; Q = 62.83, P<0.001, I² = 69.8%), which also indicated a borderline statistically significant inverse effect of parity on PC risk. No evidence of publication bias and significant heterogeneity between subgroups were detected by meta-regression analyses.

Conclusion

In summary, these findings suggest that higher parity is associated with a decreased risk of PC. Future large consortia or pooled studies are warranted to fully adjust for potential confounders to confirm this association.

Dairy products and pancreatic cancer risk: a pooled analysis of 14 cohort studies

Pancreatic cancer has few early symptoms, is usually diagnosed at late stages, and has a high case-fatality rate. Identifying modifiable risk factors is crucial to reducing pancreatic cancer morbidity and mortality. Prior studies have suggested that specific foods and nutrients, such as dairy products and constituents, may play a role in pancreatic carcinogenesis. In this pooled analysis of the primary data from 14 prospective cohort studies, 2212 incident pancreatic cancer cases were identified during follow-up among 862 680 individuals. Adjusting for smoking habits, personal history of diabetes, alcohol intake, body mass index (BMI), and energy intake, multivariable study-specific hazard ratios (MVHR) and 95% confidence intervals (CIs) were calculated using the Cox proportional hazards models and then pooled using a random effects model. There was no association between total milk intake and pancreatic cancer risk (MVHR = 0.98, 95% CI = 0.82-1.18 comparing ≥500 with 1-69.9 g/day). Similarly, intakes of low-fat milk, whole milk, cheese, cottage cheese, yogurt, and ice-cream were not associated with pancreatic cancer risk. No statistically significant association was observed between dietary (MVHR = 0.96, 95% CI = 0.77-1.19) and total calcium (MVHR = 0.89, 95% CI = 0.71-1.12) intake and pancreatic cancer risk overall when comparing intakes ≥1300 with <500 mg/day. In addition, null associations were observed for dietary and total vitamin D intake and pancreatic cancer risk. Findings were consistent within sex, smoking status, and BMI strata or when the case definition was limited to pancreatic adenocarcinoma. Overall, these findings do not support the hypothesis that consumption of dairy foods, calcium, or vitamin D during adulthood is associated with pancreatic cancer risk.