Intracranial meningioma and ionizing radiation in medical and occupational settings

Diagnostic radiological examinations and risk of intracranial tumours in adults-findings from the Interphone Study

BACKGROUND

Exposure to high doses of ionizing radiation is among the few well-established brain tumour risk factors. We used data from the Interphone study to evaluate the effects of exposure to low-dose radiation from diagnostic radiological examinations on glioma, meningioma and acoustic neuroma risk.

METHODS

Brain tumour cases (2644 gliomas, 2236 meningiomas, 1083 neuromas) diagnosed in 2000-02 were identified through hospitals in 13 countries, and 6068 controls (population-based controls in most centres) were included in the analysis. Participation across all centres was 64% for glioma cases, 78% for meningioma cases, 82% for acoustic neuroma cases and 53% for controls. Information on previous diagnostic radiological examinations was obtained by interviews, including the frequency, timing and indication for the examinations. Typical brain doses per type of examination were estimated based on the literature. Examinations within the 5 years before the index date were excluded from the dose estimation. Adjusted odds ratios were estimated using conditional logistic regression.

RESULTS

No materially or consistently increased odds ratios for glioma, meningioma or acoustic neuroma were found for any specific type of examination, including computed tomography of the head and cerebral angiography. The only indication of an elevated risk was an increasing trend in risk of meningioma with the number of isotope scans, but no such trends for other examinations were observed. No gradient was found in risk with estimated brain dose. Age at exposure did not substantially modify the findings. Sensitivity analyses gave results consistent with the main analysis.

CONCLUSIONS

There was no consistent evidence for increased risks of brain tumours with X-ray examinations, although error from selection and recall bias cannot be completely excluded. A cautious interpretation is warranted for the observed association between isotope scans and meningioma.

Molecular characteristics of meningiomas

Meningioma is the most common primary intracranial tumor in adults. The grading of meningioma is based on World Health Organization criteria, which rely on histopathological features alone. This grading system is unable to conclusively predict the clinical behavior of these tumors (i.e., recurrence or prognosis in benign or atypical grades). Advances in molecular techniques over the last decade that include genomic and epigenomic data associated with meningiomas have been used to identify genetic biomarkers that can predict tumor behavior. This review summarizes the molecular characteristics of meningioma using genetic and epigenetic biomarkers. Molecular alterations that can predict meningioma behavior may be integrated into the upcoming World Health Organization grading system.

Dental X-Rays and the Risk of Thyroid Cancer and Meningioma: A Systematic Review and Meta-Analysis of Current Epidemiological Evidence

Background: Exposure to moderate-to-high doses of ionizing radiation is the only established environmental risk factor for thyroid cancer and brain and central nervous system tumors. Considering the high lifetime prevalence and frequency of exposure to dental X-rays, the most common source of diagnostic radiation exposure in the general population, even a small associated increase in cancer risk would be of considerable public health importance. With the objective to inform clinical practice and guidelines, we synthesized the current epidemiological evidence on the association between dental X-rays and the risk of thyroid cancer, meningioma, and other cancers of the head and neck region. Methods: The Medline, Embase, and Web of Science databases were searched to identify eligible studies. Summary odds ratio/relative risk estimates and confidence intervals were extracted, and pooled risk ratios (RRs) for each cancer were calculated using random effects meta-analysis. Results: The literature search identified 5537 publications; of these, 26 studies including 10,868 cancer patients were included in the synthesis. The random effects meta-analyses, based on seven studies of thyroid cancer (six case/control, one cohort) and eight studies of meningioma (all case/control), showed that multiple (or repeated) exposures to dental X-rays were significantly associated with an increased risk of thyroid cancer (pooled RR = 1.87 [95% confidence interval, CI 1.11-3.15]) and meningioma (pooled RR = 1.53 [CI 1.26-1.85]). There was no association with glioma, and there were too few studies of other cancers of the head and neck region to conduct a meaningful meta-analysis. Conclusions: Based on a meta-analysis of retrospective case/control studies, these findings provide some support to the hypothesis that multiple (or repeated) exposures to dental X-rays may be associated with an increased risk of thyroid cancer and meningioma. These studies did not include individual organ doses and ages at exposure, and are subject to recall bias and other limitations. Furthermore, the thyroid exposure has decreased dramatically over time from the use of thyroid shields and improved technology/equipment. Prospective studies, based on dental X-ray records and patient follow-up, are needed to test the hypothesis further and clarify the possible cancer risk associated with dental radiography, as although the risk at the individual level, particularly with improved technology/equipment, is likely to be very low, the proportion of the population exposed is high. Considering that about one-third of the general population in developed countries is routinely exposed to one or more dental X-rays per year, these findings manifest the need to reduce diagnostic radiation exposure as much as possible.

Trends in intracranial meningioma incidence in the United States, 2004-2015

BACKGROUND

Meningioma incidence was reported to have risen substantially in the United States during the first decade of the 21st century. There are few reports about subsequent incidence trends. This study provides updated data to investigate trends in meningioma incidence by demographic and tumor characteristics at diagnosis in the United states from 2004 to 2015.

METHODS

Trends in meningioma incidence were analyzed using data from the Surveillance, Epidemiology, and End Results-18 (SEER-18) registry database of the National Cancer Institute. The joinpoint program was used to calculate annual percent change (APC) in incidence rates.

RESULTS

The overall incidence of meningioma increased by 4.6% (95% CI, 3.4-5.9) annually in 2004-2009, but remained stable from 2009 to 2015 (APC, 0; 95% CI, -0.8 to 0.8). Females (10.66 per 100 000 person-years) and blacks (9.52 per 100 000 person-years) had significant predominance in meningioma incidence. Incidence in many subgroups increased significantly up to 2009 and then remained stable until 2015. However, meningioma incidence in young and middle-aged people increased significantly throughout the entire time period from 2004 to 2015 (APC: 3.6% for <20-year-olds; 2.5% for 20-39-year-olds; 1.8% for 40-59-year-olds). The incidence of WHO II meningioma increased during 2011-2015 (APC = 5.4%), while the incidence of WHO III meningioma decreased during 2004-2015 (APC = -5.6%).

CONCLUSION

In this study, the incidence of meningioma was found to be stable in recent years. Possible reasons for this finding include changes in population characteristics, the widespread use of diagnostic techniques, and changes in tumor classification and risk factors in the US population.

Rare Case of Convexity Meningioma Growing into Arachnoid Cyst

BACKGROUND

Meningioma growing into an arachnoid cyst is an extremely rare event. Only 3 cases are reported in the literature. In 2 of them, an operative procedure in or near the arachnoid cyst preceded tumor growth.

CASE DESCRIPTION

We report a case of a patient requiring marsupialization of an arachnoid cyst of the middle cranial fossa. On follow-up, 3 years postoperatively he showed no signs of recurrence or tumor growth. One year later, the fourth year after surgery on the cyst, he presented with large tumor growth into the former cyst's cavity. Pathologic workup after resection revealed an atypical meningioma (World Health Organization grade II).

CONCLUSIONS

We discuss the possible pathogenesis in light of the scarce published literature, as well as the differential diagnosis of this rapidly growing tumor.

Genetic and epigenetic alterations in meningiomas

Meningiomas originate from the arachnoid layer of the meninges and divided histologically into three grades: benign (grade I), atypical (grade II), and malignant meningiomas (grade III). Genetic alterations in grade I meningiomas include frequent deletions of chromosomal locus 22q12 and NF2 gene mutations and uncommon somatic SMARCB1 and SMARCE1gene mutations; In grade II meningiomas, chromosomal losses occur on 1p, 22q, 14q, 18q, 10, and 6q, and gains on 20q, 12q, 15q, 1q, 9q, and 17q; In grade III meningiomas, losses have been recognized on 6q, 10, and 14q and alterations of PTEN, CDKN2A and CDKN2B genes. Epigenetic alterations in meningiomas include hypermethylation of the tumor suppressor genes p73 in grade I meningiomas and TIMP3 GSTP1, MEG3, HOXA6, HOXA9, PENK, WNK2 and UPK3A genes with an increasing frequency according to grade. Abnormal expression of IGF signaling family genes and Wnt signaling pathway is associated with meningioma progression. MiRNA expression profiling of meningiomas show downregulation of miR-29c-3p, miR-200a, miR-145 and miR- 219-5p and upregulation of miR-21 miR-335 and miR-190a levels. In conclusion, extensive genetic and epigenetic alterations exist in meningiomas that may help assessing prognosis. In addition, since miRNA expression may be modified by artificial miRNAs, new effective therapeutic strategies may be developed especially for resistant or high grade meningiomas.

Hormone replacement therapy and risk of meningioma in women: a meta-analysis

PURPOSE

The relationship between hormone replacement therapy (HRT) and the incidence of meningioma in women has been investigated in several epidemiologic studies, but their results were not entirely consistent. Here, we performed a meta-analysis of case-control and cohort studies to analyze this association.

METHODS

The PubMed database was searched from inception to 30 September 2012 to identify relevant studies that met pre-stated inclusion criteria. We also reviewed reference lists from the retrieved articles. Two researchers evaluated study eligibility and extracted the data independently. Odds ratios (ORs) or relative risks and 95 % confidence intervals (CIs) were extracted and pooled using the fixed-effect or random-effects models.

RESULTS

A total of 11 studies (six case-control and five cohort studies) were included in this meta-analysis, involving 1,820,954 participants, of whom 3,249 had meningioma. When compared to never users of HRT, the pooled OR with ever users for meningioma was 1.29 (95 % CI 1.03-1.60). Sensitivity analyses restricted to postmenopausal women yielded similar results (OR: 1.22; 95 % CI 1.02-1.46). Subgroup analyses showed that the pooled ORs were 1.27 (95 % CI 1.08-1.49, p < 0.05) and 1.12 (95 % CI 0.95-1.32) for current and past users of HRT, respectively.

CONCLUSION

Hormone replacement therapy use is associated with an increased risk of meningioma in women, as well as in postmenopausal women. Besides, the significant risk elevation is present in current users but not in past users. Future research should attempt to establish whether this association is causal and to clarify its mechanisms.

Cancer incidence among male Danish nurses, 1980-2003

BACKGROUND

The cancer risk of female nurses has been examined in several studies, but none has addressed the risk of male nurses, although they may be exposed to the same carcinogens as female nurses. In this register-based cohort study, we explored cancer incidence among male Danish nurses.

METHODS

We identified 3369 male nurses from the files of the Danish Nurses Association and followed them up from 1980 to 2003 in the Danish Cancer Registry. Standardized incidence ratios (SIRs) and 95% confidence intervals were calculated on the basis of standardized national rates. We compared the nurses with 3369 other male employees matched to the nurses by year of birth on social variables (vital and marital status).

FINDINGS

We observed 90 cancers in the cohort, with significantly increased SIRs for sarcomas and decreased SIRs for cancers of the respiratory system. When the cohort was stratified by educational generation and birth cohort, we observed significantly elevated relative risks for cancers of the brain and nervous system among the youngest nurses and for sarcomas among nurses in all educational generations and those born between 1945 and 1954.

CONCLUSION

The overall risk for cancer among male Danish registered nurses is similar to that of the general male Danish population. The high SIRs observed for cancers of the brain and nervous system merit further attention. The high relative risks for sarcomas and connective tissue tumours reflect a large proportion of cases of Kaposi sarcoma, which is probably not occupationally related.

Dental x-rays and the risk of thyroid cancer: a case-control study

The thyroid gland is highly susceptible to radiation carcinogenesis and exposure to high-dose ionising radiation is the only established cause of thyroid cancer. Dental radiography, a common source of low-dose diagnostic radiation exposure in the general population, is often overlooked as a radiation hazard to the gland and may be associated with the risk of thyroid cancer. An increased risk of thyroid cancer has been reported in dentists, dental assistants, and x-ray workers; and exposure to dental x-rays has been associated with an increased risk of meningiomas and salivary tumours.

METHODS

To examine whether exposure to dental x-rays was associated with the risk of thyroid cancer, we conducted a population-based case-control interview study among 313 patients with thyroid cancer and a similar number of individually matched (year of birth +/- three years, gender, nationality, district of residence) control subjects in Kuwait.

RESULTS

Conditional logistic regression analysis, adjusted for other upper-body x-rays, showed that exposure to dental x-rays was significantly associated with an increased risk of thyroid cancer (odds ratio = 2.1, 95% confidence interval: 1.4, 3.1) (p=0.001) with a dose-response pattern (p for trend <0.0001). The association did not vary appreciably by age, gender, nationality, level of education, or parity.

DISCUSSION

These findings, based on self-report by cases/controls, provide some support to the hypothesis that exposure to dental x-rays, particularly multiple exposures, may be associated with an increased risk of thyroid cancer; and warrant further study in settings where historical dental x-ray records may be available.

[Epidemiology of primary brain tumor]

Two main approaches are generally used to study the epidemiology of primary brain tumors. The first approach is to identify risk factors, which may be intrinsic or related to external causes. The second main approach is descriptive. Intrinsic factors potentially affecting risk include genetic predisposition and susceptibility, gender, race, birth weight and allergy. Radiation exposure is the main extrinsic factor affecting risk. A large body of work devoted, among others, to electromagnetic fields and especially cellular phones, substitutive hormonal therapy, pesticides, and diet have been published. To date, results have been discordant. Descriptive epidemiological studies have reported an increasing annual incidence of primary brain tumors in industrialized countries. The main reasons are the increasing age of the population and better access to diagnostic imaging. Comparing incidences from one registry to another is difficult. Spatial and temporal variations constitute one explanation and evolutions in coding methods another. In all registries, weak incidence of primary brain tumors constitute a very important limiting factor. Renewed interest from the neuro-oncological community is needed to obtain pertinent and essential data which could facilitate improved knowledge on this topic.

Radiation-induced meningiomas: a shadow in the success story of childhood leukemia

While the prognosis of acute childhood leukemia has improved, long-term survivors are increasingly experiencing late effects of the treatment. Cranially irradiated survivors are predisposed to the development of CNS tumors. Our aim was to describe the incidence of secondary brain tumors and to define the significance of treatment-related risk factors and host characteristics in a cohort of childhood leukemia survivors. Our cohort consisted of 60 consecutive cranially irradiated adult survivors of childhood leukemia treated in Oulu University Hospital (Oulu, Finland); MRI of the brain was performed on 49. The sites of the tumors, their histology, and details of the leukemia treatment were determined. Of the 49 patients, 11 (22%) 1-8 years of age at the time of diagnosis developed meningioma later in life, while no other brain tumors were seen. In this cohort, the development of meningioma seemed to show undisputable linkage with long latency periods (mean, 25 years; range, 14-34 years) and an increasing incidence 20 years after the treatment (47%). Three patients had multiple meningiomas, two had recurrent disease, and one had an atypical meningioma. Age at the time of irradiation, gender, or cumulative doses of chemotherapeutic agents showed no significant association with the development of meningiomas. The high incidence of meningiomas in this study was associated with long follow-up periods. Although the cohort is small, it seems probable that the increasing incidence of meningioma will shadow the future of cranially irradiated leukemia survivors. Systematic brain imaging after the treatment is therefore justifiable.

MRI of radiation-induced tumors of the head and neck in post-radiation nasopharyngeal carcinoma

The aim of this study was to document the sites and MRI features of radiation-induced tumors (RITs) in the head and neck following treatment for nasopharyngeal carcinoma (NPC). The MRI examinations and clinical records of 20 patients with 21 RITs were reviewed retrospectively. RITs developed 3-30 years after radiotherapy and included eleven squamous cell carcinomas, six sarcomas, two neuroendocrine carcinomas, one mucoepidermoid carcinoma and one meningioma. RITs arose in the maxillary region (9), oro/hypopharynx and oral cavity (5), external auditory canal (4), nasopharynx and sphenoid sinus (2) and brain (1). Radiation-induced carcinoma and sarcoma had MRI features that were useful to distinguish them from recurrent NPC. To improve early detection of RITs, the check areas on an MRI of a patient with previous NPC treated by radiation should always include the maxillary region, tongue, and external auditory canal/temporal bone.

Meningiomas: causes and risk factors

Meningiomas are among the most common primary intracranial tumors. Although the vast majority of these tumors are considered histologically benign, the incidence of complications can be high. Few studies have investigated the causes and risk factors for meningioma; this review highlights the current state of knowledge. Gaining a better understanding of the origin of this disease is essential so that treatments and outcomes can be improved and prevention strategies can be developed.

Medical exposure to ionising radiation and the risk of brain tumours: Interphone study group, Germany

BACKGROUND

The role of exposure to low doses of ionising radiation in the aetiology of brain tumours has yet to be clarified. The objective of this study was to investigate the association between medically or occupationally related exposure to ionising radiation and brain tumours.

METHODS

We used self-reported medical and occupational data collected during the German part of a multinational case-control study on mobile phone use and the risk of brain tumours (Interphone study) for the analyses.

RESULTS

For any exposure to medical ionising radiation we found odds ratios (ORs) of 0.63 (95% confidence interval (CI)=0.48-0.83), 1.08 (95% CI=0.80-1.45) and 0.97 (95% CI=0.54-1.75) for glioma, meningioma and acoustic neuroma, respectively. Elevated ORs were found for meningioma (OR 2.32, 95% CI: 0.90-5.96) and acoustic neuroma (OR 6.45, 95% CI: 0.62-67.16) for radiotherapy to the head and neck regions.

CONCLUSION

We did not find any significant increased risk of brain tumours for exposure to medical ionising radiation.