Malignant Tumors of the Central Nervous System

Malignant tumors of the central nervous system in adults comprise a heterogeneous group of malignancies, the largest subgroups comprising astrocytomas, ependymomas, and oligodendrogliomas. Glioblastomas are the most common tumor type, and they have dismal prognosis. Due to differences in cell type of origin, as well as pathogenesis, it is plausible that their etiology also differs between tumor types. The etiology of malignant CNS tumors is largely unknown and no occupational risk factors have been definitively identified. High doses of ionizing radiation increase the risk, but in occupational settings the dose levels appear too small to result in discernible excesses. Several studies have assessed possible effect of extremely low frequency and radiofrequency electromagnetic fields, but the results are inconsistent. Increased brain tumor risk has been reported in agricultural workers, but no specific exposure has been linked to them. Pesticides have been analyzed in several studies without showing a clear increase in risk.acceptedVersionPeer reviewe

A pooled multisite analysis of the effects of female reproductive hormones on glioma risk

PURPOSE: The association between female reproductive factors and glioma risk is unclear, but most published studies have been limited by small sample size. We conducted a pooled multisite study of pre- and post-menopausal women, investigating the effect of female reproductive factors, including hormonal medications. METHODS: Unconditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals assessing the effects of female reproductive factors and female hormonal medications in glioma cases and unrelated controls. RESULTS: Menarche over the age of 15 as compared to under 12 was associated with a statistically significant risk for glioma (OR = 2.00, 95% CI, 1.47–2.71). Use of Oral Contraceptive Pills (OCP) was inversely associated with risk of glioma (OR= 0.61, 95% CI, 0.50–0.74) and there was an inverse trend with longer duration of OCP use (p for trend< 0.0001). Use of Hormone Replacement Therapy (HRT) was also inversely associated with risk of glioma (OR=0.55, 95% CI, 0.44–0.68) and there was an inverse trend with longer duration of use (p for trend< 0.0001). Compared to those reporting neither OCP use nor HRT use, those who reported using both were less likely to have a diagnosis of glioma (OR = 0.34, 95% CI, 0.24–0.48). CONCLUSIONS: Female reproductive hormones may decrease the risk for glioma. The association appears to be strongest with greater length of use and use of both HRT and OCP