Incidence Rates in Low-Grade Primary Brain Tumors: Are There Differences Between Men and Women? A Systematic Review

BACKGROUND: Incidence rates of adult low-grade primary brain tumors have previously been widely analyzed nationwide across the world, and most of these studies include data on incidence rates in men and women separately. However, to our knowledge, no worldwide international comparison has been made on possible differences in incidence rates of low-grade brain tumors between men and women. The primary aim was to review the incidence rates between men and women in adult low-grade primary brain tumors. METHODS: We searched for published articles in internationally peer reviewed journals that were identified through a systematic search of PubMed. Because of difficulties in interpreting data, we excluded all studies only including patient data before the second edition of World Health Organization (WHO) histological classification system of brain tumors (1993). We also made an overall analysis to calculate incidence rates of low-grade brain tumors in men and women separately. RESULTS: A total of 14 studies from the United States and Europe were reviewed. Overall mean age-adjusted incidence rate in men was 1.07 per 100,000 compared to 1.70 per 100,000 in women. No significant difference was seen in age-adjusted incidence rate between genders (Mann-Whitney U test; P = 0.8347). No significant trend of age-adjusted incidence rate was seen in male patients (P = 0.757) nor in women (P = 0.354). CONCLUSION: The results must be interpreted with caution and more large international studies are warranted and should be made in a standardized manner differing low-grade tumors from high-grade tumors according to the WHO 2007 brain tumor classification system. Also future studies should always state the ICD-O histology coding to ease future interpretations.