Time trends in malignant brain tumors in the United States: SEER 1975-2008

This study evaluates incidence time trends of malignant brain tumors by primary sites and histological subtypes in the US.

SEER*Stat was used to obtain age, sex, year, and histologic-specific incidence rate in SEER 9 Registry between 1975 and 2008. Primary sites and histologic subtypes of malignant brain tumors were identified based on ICD-O-3 codes. Annual percent change (APC) of sex-specific brain tumor incidence by primary site was estimated by Joinpoint regression. Joinpoint was also used to estimate sex- and age-specific time trends by histologic subtypes of brain tumors.

Between 1975 and 2008, incidence for all malignant brain tumors was stable in men (APC=0.11, p=0.25) but slightly increasing in women (APC=0.20%, p=0.05). Malignant brain tumor of frontal lobe, temporal lobe and brain stem was significantly increasing for both men and women, while brain tumor of cerebrum and parietal lobe was decreasing overtime. Glioma incidence increased significantly in men under age of 40 with an overall 2.3% estimated APC increase (p<0.01). Likewise, glioma increased in females under age of 30 (APC=1.5% and 2.8% for age group <20 and 20-29, respectively, p<0.01). Incidence for astrocytoma, glioblastoma, and oligodendroglioma was found to decrease for all age group over the past three decades. These increased rates for specific primary sites and glioma in young-persons cannot be fully explained by diagnostic improvement and may reflect some environmental risk factors. Among the hypotheses that should be explored are documented increased use of diagnostic radiation and growing use of cellphones, or still to be discovered other risk factors.