Diagnosis and prognosis of brain tumors in clinical trials

According to the Central Brain Registry Of The United States (CBTRUS) statistical report (February 2012) the incidence rate of all primary non malignant and malignant brain and central nervous system tumors is 19.89 cases per 100.000 (11.58 for non-malignant tumors and 7.31 for malignant tumors). Malignant brain tumors account for only 1% to 2% of all adult cancers. As a comparison, in 2012, the incidence of women breast cancer was 121.2 (per 100.000). Tumors of neuroepithelial tissue are the most frequent malignant brain tumors with an incidence rate of 6.16. The most common tumor of neuroepithelial tissue is the glioblastoma (GBM) with an incidence of 3.2. Other histologies e.g. astrocytoma, oligodendroglioma or mixed oligoastrocytoma have an incidence rate lower than 0.5. 1,2 The incidence of brain tumors increases with age, with an incidence rate is 8.59 for young patients (age 20-34) and 55.8 for elderly patients (age 65-74). Age distributions also differ by histology and grade. Glioblastoma peaks in incidence at age 65-74 and oligodendroglioma and low grade astrocytoma at age 35-44. Causes of brain tumors are still largely unknown. Various categories of risk factors are investigated in epidemiologic studies: geographic and ethnic, environmental (irradiation, pollution), lifestyle (food, alcohol, smoking bits, use of cell phone), medical treatments and conditions (allergies, infections), familial or hereditary. To date, inherited genetic syndromes, therapeutic ionizing irradiation are the only generally accepted risk factors of glioma genesis.4,5 In the last decade, advances in microarray and sequencing technologies allowed the realization of large gene expression and genome wide association studies (GWAS). Recently, two GWAS provided more insight into the genetic variants that influence an individual susceptibility to develop gliomas. 6,7,8 In addition to germline genetic risk factors, recent studies showed that acquired somatic genetic changes were associated with treatment response, disease progression and overall survival.9,10