Modifiable risk factors for glioblastoma: a systematic review and meta-analysis

Neurosurgical review · 2023 · No effect · High evidence

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No effectHigh evidencePaper 452

Study snapshot

PublicationNeurosurgical review · 2023

Study typemeta_analysis

Reported directionNo effect

Evidence ratingHigh

Abstract

Modifiable risk factors for glioblastoma: a systematic review and meta-analysis Yoshikawa MH, Rabelo NN, Telles JPM, Figueiredo EG. Modifiable risk factors for glioblastoma: a systematic review and meta-analysis. Neurosurg Rev. 2023 Jun 20;46(1):143. doi: 10.1007/s10143-023-02051-y. Abstract Glioblastoma (GBM) is the most common and aggressive glioma histological subtype, associated with high disability and poor survival. The etiology of this condition is still mostly unknown, and evidence about risk factors is elusive. The aim of this study is to identify modifiable risk factors for GBM. Electronic search was performed by two reviewers independently using the keywords and MeSH terms 'glioblastoma' OR 'glioma' OR 'brain tumor' AND 'risk factor'. The inclusion criteria were (1) observational studies or experimental studies on humans, (2) studies assessing the association between glioblastoma and exposure to modifiable conditions, and (3) studies published in English or Portuguese. Studies on the pediatric population or about exposure to ionizing radiation were excluded. A total of 12 studies were included. Seven were case-control studies, and five were cohort studies. The risk factors assessed included body mass index, alcohol consumption, exposure to magnetic fields, diabetes mellitus type 2 (DM2), and use of non-steroidal anti-inflammatory drugs (NSAID). No significant link was found between GBM incidence and DM2 or magnetic field exposure. On the other hand, higher BMI, alcohol consumption, and NSAID use demonstrated a protective effect on GMB risk. However, given the limited number of studies, it is not possible to obtain a behavioral recommendation; instead, these findings are relevant to guide future basic scientific studies on GBM oncogenesis. pubmed.ncbi.nlm.nih.gov Excerpts Exposure to magnetic fields Two studies (Table 2) analyzed the exposure to magnetic fields as a risk factor for GBM (Fig. 3). Villeneuve et al. [17] performed a population-based case–control study with 156 controls and 143 cases, using data collected through the Canadian National Enhanced Cancer Surveillance System (NECSS), finding a positive association between exposure and risk of GBM in subjects exposed to magnetic fields ≥ 6 mT (OR 5.36; CI95% 1.16–24.78). Cases and controls were matched by age. Thérinault et al. [18], on the other hand, investigated a population of 65 controls and 18 cases drawn from three cohorts of male employees of electric utilities – Électricité de France-Gaz de France (EDF), Ontario Hydro (OH) and Hydro-Quebec (HQ) – finding no significative association or dose–response relationship (Table 4). Cases and controls were matched by age. The EDF cohort (n = 170,000) did not include cases older than 60 years and did not follow participants after the termination of employment, while OH (n = 31,543) and HQ (n = 21.749) included all employees at the beginning of the study and new one, following them to their deaths. The statistical analysis demonstrated no association between magnetic field exposure and GBM risk (OR 1.37; CI95% 0.70–2.04). Exposure to magnetic fields Previous in vivo and in vitro studies have demonstrated that prolonged exposures to magnetic fields induce the carcinogenic process [36]. In this review, no significant association was found between exposure to magnetic fields and GBM risk. Among the two studies on this topic included in the present review, one demonstrated a positive association [17]. The study with positive results was population-based and assessed self-reported residential and occupational magnetic field exposure, finding that subjects exposed to magnetic fields ≥ 0.6 µT were at higher risk of developing GBM [17]. Although the study design allowed greater external validity, it is more prone to reporting bias and has a less accurate measure of exposure. On the other hand, the study with no significant association between the level of exposure and the risk of GBM used standardized and more accurate assessment of levels of exposure but has as limitations that most parts of the cohort were not followed when patients were 60 years of age or older, decreasing the power of the analysis [18]. Limitations The main limitation of this review is the small number of studies included, which impaired the quantitative analysis and the drawn of conclusions. Additional and more robust studies are necessary to evaluate if the tendencies found by this meta-analysis derive from a true association or random chance. Other limitations include heterogeneity between studies regarding the assessment and definition of exposures and the use of self-reported information as a measure of exposure by many studies – which, in the setting of a disease that affects memory, is prone to recall bias. Conclusion No significant link was found between GBM incidence and DM2 or magnetic field exposure. On the other hand, higher BMI, alcohol consumption, and NSAID use demonstrated a protective effect on GMB risk. However, given the limited number of studies, it is not possible to obtain a behavioral recommendation; instead, these findings are relevant to guide future basic scientific studies on GBM oncogenesis.

Machine Enhanced Logic

AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typemeta_analysis

Effect directionno_effect

PopulationHumans (observational studies; adult/non-pediatric implied)

Sample sizeNot supplied

ExposureELF

Evidence strengthHighConfidence: 78% · Peer reviewed: yes

Main findings

This systematic review and meta-analysis included 12 human studies assessing modifiable risk factors for glioblastoma, including magnetic field exposure. The pooled analysis reported no significant association between magnetic field exposure and GBM risk (reported OR 1.37; 95% CI 0.70–2.04), although one included case-control study reported a positive association at higher exposure levels.

Outcomes measured

Glioblastoma (GBM) incidence/risk

Limitations

Small number of included studies, limiting quantitative analysis and strength of conclusions
Heterogeneity across studies in exposure assessment and exposure definitions
Use of self-reported exposure information in some studies, raising potential recall/reporting bias
Potential limited follow-up/age coverage in one occupational cohort (e.g., not including cases older than 60 years and not following after employment termination), reducing power

View raw extracted JSON

{
  "publication_year": 2023,
  "study_type": "meta_analysis",
  "exposure": {
    "band": "ELF",
    "source": "occupational/residential magnetic field exposure",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": "Humans (observational studies; adult/non-pediatric implied)",
  "sample_size": null,
  "outcomes": [
    "Glioblastoma (GBM) incidence/risk"
  ],
  "main_findings": "This systematic review and meta-analysis included 12 human studies assessing modifiable risk factors for glioblastoma, including magnetic field exposure. The pooled analysis reported no significant association between magnetic field exposure and GBM risk (reported OR 1.37; 95% CI 0.70–2.04), although one included case-control study reported a positive association at higher exposure levels.",
  "effect_direction": "no_effect",
  "limitations": [
    "Small number of included studies, limiting quantitative analysis and strength of conclusions",
    "Heterogeneity across studies in exposure assessment and exposure definitions",
    "Use of self-reported exposure information in some studies, raising potential recall/reporting bias",
    "Potential limited follow-up/age coverage in one occupational cohort (e.g., not including cases older than 60 years and not following after employment termination), reducing power"
  ],
  "evidence_strength": "high",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "stance": "reassurance",
  "stance_confidence": 0.66,
  "summary": "This 2023 systematic review and meta-analysis evaluated modifiable risk factors for glioblastoma using 12 human observational studies (7 case-control, 5 cohort). For magnetic field exposure, the meta-analysis reported no significant association with glioblastoma risk (OR 1.37; 95% CI 0.70–2.04), despite one included study reporting a positive association at higher exposure levels. The authors emphasize that the small number of studies and heterogeneous exposure assessment limit firm conclusions.",
  "key_points": [
    "The review aimed to identify modifiable risk factors for glioblastoma and included 12 human observational studies.",
    "Magnetic field exposure was assessed in two included studies, with one reporting a positive association at higher exposure levels and one reporting no association.",
    "The meta-analysis reported no significant association between magnetic field exposure and glioblastoma risk (OR 1.37; 95% CI 0.70–2.04).",
    "The authors note substantial limitations including few studies and heterogeneity in exposure measurement and definitions.",
    "Self-reported exposure in some studies was highlighted as prone to reporting/recall bias.",
    "The authors state the evidence is insufficient to support behavioral recommendations and suggest findings mainly guide future research."
  ],
  "categories": [
    "Cancer",
    "ELF Magnetic Fields",
    "Occupational Exposure",
    "Epidemiology",
    "Systematic Reviews & Meta-Analyses"
  ],
  "tags": [
    "Glioblastoma",
    "Brain Tumor Risk",
    "Systematic Review",
    "Meta-Analysis",
    "Magnetic Field Exposure",
    "ELF Exposure",
    "Occupational Exposure",
    "Residential Exposure",
    "Case-Control Studies",
    "Cohort Studies",
    "Recall Bias",
    "Exposure Assessment"
  ],
  "keywords": [
    "glioblastoma",
    "glioma",
    "brain tumor",
    "risk factor",
    "magnetic fields",
    "meta-analysis",
    "systematic review",
    "case-control",
    "cohort"
  ],
  "suggested_hubs": [
    {
      "slug": "occupational-exposure",
      "weight": 0.72,
      "reason": "Includes occupational magnetic field exposure studies in electric utility workers."
    },
    {
      "slug": "power-lines",
      "weight": 0.46,
      "reason": "Addresses ELF magnetic field exposure as a potential cancer risk factor, relevant to power-frequency field discussions."
    }
  ],
  "social": {
    "tweet": "Systematic review/meta-analysis (2023) of modifiable GBM risk factors: pooled results reported no significant association between magnetic field exposure and glioblastoma risk (OR 1.37; 95% CI 0.70–2.04), though evidence is limited and heterogeneous.",
    "facebook": "A 2023 systematic review and meta-analysis of 12 human observational studies examined modifiable risk factors for glioblastoma. For magnetic field exposure, the pooled analysis reported no significant association with GBM risk (OR 1.37; 95% CI 0.70–2.04), but the authors note few studies and varied exposure assessment limit conclusions.",
    "linkedin": "Neurosurgical Review (2023): systematic review and meta-analysis of modifiable glioblastoma risk factors (12 observational studies). For magnetic field exposure, the pooled estimate showed no significant association with GBM risk (OR 1.37; 95% CI 0.70–2.04). Authors highlight limited study numbers and heterogeneous exposure assessment as key constraints."
  }
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1007/s10143-023-02051-y
PubMed: 37340151

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