Central Nervous System Tumors

Central nervous system (CNS) tumors with specific, anatomic, physiological, and functional unique characteristics are challenging tumors that account for fewer than 3% of all neoplasms. Clinical presentation of CNS tumors is diffuse and varied with high dependency on anatomic location. While a sacrococcygeal tumor may present with intractable nerve or bone pain, a hypothalamus tumor may cause endocrinopathy, an occipital tumor may cause visual problems, whereas seizures may be the presenting symptom for cortex tumors. Majority of CNS cell populations have low mitotic index with slow proliferation that they are radiobiologically considered to be late-responding tissues. Advances in radiation oncology techniques now offer promising opportunities to alter the CNS tumor therapeutic index such as optic apparatus avoidance during stereotactic radiosurgery to prevent blindness, cochlear sparing in pediatric posterior fossa IMRT to spare hearing, endocrinopathy avoidance by dose minimization to hypothalamopituitary axis, and hippocampal avoidance to decrease cognitive decline. Basic concepts that are crucial to understanding central nervous system tumors are reviewed in depth in this chapter.