Hormone replacement therapy and risk of glioma: a nationwide nested case-control study

Does exogenous hormonal therapy affect the risk of glioma among females: A systematic review and meta-analysis

Background

The effect of exogenous hormone replacement therapy (HRT) and oral contraceptive pills (OCPs) on glioma risk in females is unclear despite numerous studies; hence, we conducted a meta-analysis to evaluate this relationship.

Methods

Studies investigating the impact of exogenous female hormones on glioma risk were retrieved by searching 4 databases from inception until September 2022. Articles of any design, such as case-control and cohort studies, proving the relative risk (RR), odds ratio (OR), or hazard ratio were included. Summary OR values were calculated using a random effects model.

Results

Both HRT and OCP use of any duration decreased the risk of developing glioma [HRT OR = 0.78, 95% CI 0.66-0.91, P = .00; OCP: OR = 0.80, 95% CI 0.67-0.96, P = .02]. When stratified by duration of use, HRT use >1 year significantly reduced glioma risk (<1 year: OR = 0.82, 95% CI 0.63-1.07, P = 0.15; 1-5 years: OR = 0.79, 95% CI 0.67-0.92, P = .00; 5-10 years: OR = 0.80, 95% CI 0.66-0.97, P = .02; >10 years: OR = 0.69, 95% CI 0.54-0.88, P = .00). In contrast, only OCP use for >10 years significantly reduced glioma risk (<1 year: OR = 0.72, 95% CI 0.49-1.05, P = .09; 1-5 years: OR = 0.88, 95% CI 0.72-1.02, P = .09; 5-10 years: OR = 0.85, 95% CI 0.65-1.1, P = 0.21; >10 years: OR = 0.58, 95% CI 0.45-0.74, P = .00).

Conclusions

Our pooled results strongly suggest that sustained HRT and OCP use is associated with reduced risk of glioma development.

Menopausal hormone therapy and central nervous system tumors: Danish nested case-control study

BACKGROUND

Use of estrogen-containing menopausal hormone therapy has been shown to influence the risk of central nervous system (CNS) tumors. However, it is unknown how the progestin-component affects the risk and whether continuous versus cyclic treatment regimens influence the risk differently.

METHODS AND FINDINGS

Nested case-control studies within a nationwide cohort of Danish women followed for 19 years from 2000 to 2018. The cohort comprised 789,901 women aged 50 to 60 years during follow-up, without prior CNS tumor diagnosis, cancer, or contraindication for treatment with menopausal hormone therapy. Information on cumulative exposure to female hormonal drugs was based on filled prescriptions. Statistical analysis included educational level, use of antihistamines, and use of anti-asthma drugs as covariates. During follow-up, 1,595 women were diagnosed with meningioma and 1,167 with glioma. The median (first-third quartile) follow-up time of individuals in the full cohort was 10.8 years (5.0 years to 17.5 years). Compared to never-use, exposure to estrogen-progestin or progestin-only were both associated with increased risk of meningioma, hazard ratio (HR) 1.21; (95% confidence interval (CI) [1.06, 1.37] p = 0.005) and HR 1.28; (95% CI [1.05, 1.54] p = 0.012), respectively. Corresponding HRs for glioma were HR 1.00; (95% CI [0.86, 1.16] p = 0.982) and HR 1.20; (95% CI [0.95, 1.51] p = 0.117). Continuous estrogen-progestin exhibited higher HR of meningioma 1.34; (95% CI [1.08, 1.66] p = 0.008) than cyclic treatment 1.13; (95% CI [0.94, 1.34] p = 0.185). Previous use of estrogen-progestin 5 to 10 years prior to diagnosis yielded the strongest association with meningioma, HR 1.26; (95% CI [1.01, 1.57] p = 0.044), whereas current/recent use of progestin-only yielded the highest HRs for both meningioma 1.64; (95% CI [0.90, 2.98] p = 0.104) and glioma 1.83; (95% CI [0.98, 3.41] p = 0.057). Being an observational study, residual confounding could occur.

CONCLUSIONS

Use of continuous, but not cyclic estrogen-progestin was associated with increased meningioma risk. There was no evidence of increased glioma risk with estrogen-progestin use. Use of progestin-only was associated with increased risk of meningioma and potentially glioma. Further studies are warranted to evaluate our findings and investigate the influence of long-term progestin-only regimens on CNS tumor risk.

Central nervous system tumours among users of vaginal oestradiol tablets: A nationwide population-based study

BACKGROUND AND PURPOSE

It is currently unknown whether vaginal oestradiol is associated with development of meningioma and glioma. The aim of this study was to examine associations between cumulative use and treatment intensity of vaginally administered oestradiol tablets and incidence of meningioma and glioma in a nationwide, population-based study.

METHODS

We conducted a nested case-control study within a nationwide cohort of Danish women followed from 2000 to 2018. The cohort consisted of 590,676 women aged 50-60 years at study start, without prior cancer diagnosis or use of systemic hormone therapy. Information on cumulative dose, duration, and intensity of vaginal oestradiol tablet use was assessed from filled prescriptions. Conditional logistic regression provided adjusted hazard ratios (HRs) for the association between vaginal oestradiol use and diagnosis of meningioma or glioma.

RESULTS

We identified 1108 women with meningioma and 835 with glioma. Of these, 19.8% and 14.0% used vaginal oestradiol tablets, respectively. The HRs in those with ever-use of vaginal oestradiol tablets was 1.14 (95% confidence interval [CI] 0.97-1.34) for meningioma and 0.90 (95% CI 0.73-1.11) for glioma. The corresponding HRs for new users exclusively were 1.18 (95% CI 0.99-1.40) for meningioma and 0.89 (95% CI 0.71-1.13) for glioma. Intensity of vaginal oestradiol tablet use according to duration and user status yielded slightly elevated HRs for meningioma without an apparent dose-response pattern, while the HRs for glioma were generally below unity. Among new users, the HR with high intensity of current or recent vaginal oestradiol tablet use for 2+ years was 1.66 (95% CI 1.09-2.55) for meningioma and 0.77 (95% CI 0.41-1.44) for glioma.

CONCLUSION

Use of vaginal oestradiol tablets was associated with a slightly increased incidence of meningioma but not of glioma. Owing to the observational nature of the study, residual bias cannot be ruled out.

Components of particulate matter air-pollution and brain tumors

BACKGROUND

Air pollution is an established carcinogen. Evidence for an association with brain tumors is, however, inconclusive. We investigated if individual particulate matter constituents were associated with brain tumor risk.

METHODS

From comprehensive national registers, we identified all (n = 12 928) brain tumor cases, diagnosed in Denmark in the period 1989-2014, and selected 22 961 controls, matched on age, sex and year of birth. We established address histories and estimated 10-year mean residential outdoor concentrations of particulate matter < 2.5 µm, primarily emitted black carbon (BC) and organic carbon (OC), and combined carbon (OC/BC), as well as secondary inorganic and organic PM air pollutants from a detailed dispersion model. We used conditional logistic regression to calculate odds ratios (OR) per inter quartile range (IQR) exposure. We adjusted for income, marital and employment status as well as area-level socio-demographic characteristics.

RESULTS

Total tumors of the brain were associated with OC/BC (OR: 1.053, 95%CI: 1.005-1.103, per IQR). The data suggested strongest associations for malignant tumors with ORs per IQR for OC/BC, BC and OC of 1.063 (95% CI: 1.007-1.123), 1.036 (95% CI: 1.006-1.067) and 1.030 (95%CI: 0.979-1.085), respectively. The results did not indicate adverse effects of other PM components.

CONCLUSIONS

This large, population based study showed associations between primary emitted carbonaceous particles and risk for malignant brain tumors. As the first of its kind, this study needs replication.

Sex Hormones and Optic Nerve Disorders: A Review

Aim: This review article presents a comprehensive overview of the literature on sex hormones (estrogens, androgens, progesterone) and optic nerve disorders, with a discussion of the implications for therapy and prevention.

Methods: Epidemiological, pre-clinical and clinical studies were reviewed.

Results: Analysis of the biological basis for a relationship between eye diseases and sex hormones showed that some types of hormones can exert a protective effect either directly on the retina and optic nerve or indirectly by modulating ocular blood flow. For example, it seems that estrogen exposure has a protective effect against glaucoma, whereas its deficit may lead to early onset of the disease. If further studies confirm the data in the literature, estrogen therapy, because of its antioxidant action, may be effective in the treatment of Leber's hereditary optic neuropathy, whereas, in the light of current studies, there does not seem to be an influence of estrogen on non-arteritic anterior ischemic optic neuritis (NAION).

Conclusions: Although there is some evidence that in some optic nerve pathologies the sex hormones seem to play an important role there are still too few studies providing evidence for its wider use in clinical practice.

Study designs may influence results: the problems with questionnaire-based case-control studies on the epidemiology of glioma

Glioma is a rare brain tumour with a very poor prognosis and the search for modifiable factors is intense. We reviewed the literature concerning risk factors for glioma obtained in case-control designed epidemiological studies in order to discuss the influence of this methodology on the observed results. When reviewing the association between three exposures, medical radiation, exogenous hormone use and allergy, we critically appraised the evidence from both case-control and cohort studies. For medical radiation and hormone replacement therapy (HRT), questionnaire-based case-control studies appeared to show an inverse association, whereas nested case-control and cohort studies showed no association. For allergies, the inverse association was observed irrespective of study design. We recommend that the questionnaire-based case-control design be placed lower in the hierarchy of studies for establishing cause-and-effect for diseases such as glioma. We suggest that a state-of-the-art case-control study should, as a minimum, be accompanied by extensive validation of the exposure assessment methods and the representativeness of the study sample with regard to the exposures of interest. Otherwise, such studies cannot be regarded as 'hypothesis testing' but only 'hypothesis generating'. We consider that this holds true for all questionnaire-based case-control studies on cancer and other chronic diseases, although perhaps not to the same extent for each exposure-outcome combination.

Cancer risk among parous women following assisted reproductive technology

STUDY QUESTION

Do women who give birth after assisted reproductive technology (ART) have an increased risk of cancer compared with women who give birth without ART?

SUMMARY ANSWER

Without correction, the results indicate an increase in overall cancer risk, as well as a 50% increase in risk of CNS cancer for women giving birth after ART, however the results were not significant after correcting for multiple analyses.

WHAT IS KNOWN ALREADY

Studies regarding the effects of hormonal treatments involved with ART on subsequent cancer risk have provided inconsistent results, and it has also been suggested that infertility itself could be a contributory factor.

STUDY DESIGN, SIZE, DURATION

A population-based cohort consisting of all women registered in the Medical Birth Registry of Norway as having given birth between 1 January 1984 and 31 December 2010 was assembled (n = 812 986). Cancers were identified by linkage to the Cancer Registry of Norway. Study subjects were followed from start of first pregnancy during the observational period until the first cancer, death, emigration, or 31 December 2010.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Of the total study population (n = 806 248), 16 525 gave birth to a child following ART. Cox regression analysis computed hazard ratios (HR) and 95% confidence intervals (CI) comparing cancer risk between ART women and non-ART women; for overall cancer, and for cervical, ovarian, uterine, central nervous system (CNS), colorectal and thyroid cancers, and for malignant melanoma.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 22 282 cohort members were diagnosed with cancer, of which 338 were ART women and 21 944 non-ART women. The results showed an elevated risk in one out of seven sites for ART women. The HR for cancer of the CNS was 1.50 (95% CI 1.03- 2.18), and among those specifically subjected to IVF (without ICSI) the HR was 1.83 (95% CI 1.22-2.73). Analysis of risk of overall cancer gave an HR of 1.16 (95% CI 1.04-1.29). Among those who had delivered only one child by the end of follow-up, the HR for ovarian cancer was 2.00 (95% CI 1.08-3.65), and for those nulliparous at entry the HR was 1.80 (95% CI 1.04-3.11). However, all findings became non-significant after correcting for multiple analyses.

LIMITATIONS, REASONS FOR CAUTION

The results of elevated risk of overall cancer and CNS cancer lost significance when adjusting for multiple analyses, implying an important limitation of the study. The follow-up time was relatively short, especially for ART women. In addition, as the cohort was relatively young, there were few incident cancers, especially for some rarer cancer forms, such as uterine cancer. Risk assessments according to different causes of infertility could not be done.

WIDER IMPLICATIONS OF THE FINDINGS

In light of the findings in the present study, further studies should be made on risk of CNS and ovarian cancer, and continued monitoring of all those treated with ART is encouraged. Our findings may only be generalizable to women who give birth after ART, and the risk for women who remain nulliparous after ART remains to be assessed.

STUDY FUNDING/COMPETING INTEREST

The study was funded by the Norwegian National Advisory Unit on Women's Health. All authors claim no competing interests.

Menopausal hormone therapy and central nervous system tumor risk: large UK prospective study and meta-analysis

Female sex hormones are thought to affect women's risk of developing central nervous system (CNS) tumors. Some have reported an increased risk in users of menopausal hormone therapy (HT) but evidence is limited. In the UK General Practice Research Database we compared prospectively collected information on HT prescriptions in women aged 50-79 years with CNS tumors diagnosed in 1987-2011 with that in matched controls (four per case). Relative risks (RRs) in relation to prescribed HT were calculated overall and by CNS tumor subtype. Statistical tests are two-sided. For all CNS tumors (n = 3,500), glioma (n = 689), meningioma (n = 1,197), acoustic neuroma (n = 439), and pituitary tumors (n = 273) adjusted RRs for women prescribed HT versus not were, respectively, 1.21 (95% confidence intervals (CI) = 1.10-1.32, p < 0.0001), 1.14 (0.93-1.40, p = 0.2), 1.30 (1.11-1.51, p = 0.001), 1.37 (1.06-1.75, p = 0.01), and 1.35 (0.99-1.85, p = 0.06). There was no significant difference in risk by tumor subtype (p(heterogeneity) = 0.6). A meta-analysis was conducted, combining our results with those from other published studies with prospectively collected exposure information. The meta-analyses yielded significantly increased risks for all CNS tumors, glioma and meningioma in users of estrogen-only [1.35 (1.22-1.49), 1.23 (1.06-1.42) and 1.31 (1.20-1.43), respectively] but not estrogen-progestin HT [1.09 (0.99-1.19), 0.92 (0.78-1.08) and 1.05 (0.95-1.16), respectively]; these differences were statistically significant (p < 0.005 for each tumor type). There was no significant difference between glioma and meningioma risk in users of estrogen-only HT. The totality of the available evidence suggests an increased risk of all CNS tumors (and of glioma and meningioma separately) in users of estrogen-only HT. Absolute excess risk (2 per 10,000 users over 5 years) is small.