Hippocampal Prophylactic Cranial Irradiation for Small Cell Lung Cancer

The standard of care in management of small cell lung cancer consists of chemotherapy plus thoracic radiation followed by prophylactic cranial irradiation (PCI) based on a randomized trial that demonstrated a significant improvement in overall survival (OS) with PCI. Unfortunately radiation therapy to the brain is associated with neurocognitive toxicity, which may be at least in part related to radiation induced injury to neural progenitor cells in the hippocampus. Both human and animal data suggest an inverse relationship between radiation dose to the hippocampus and performance on neuropsychological testing. We hypothesize that hippocampal sparing PCI will allow improved performance on tests of short term memory and executive function compared to a historical control (RTOG 0212) receiving the same dose of conventional PCI. The primary objective of this study is to evaluate performance on the Hopkins Verbal Learning Test-Revised for delayed recall at 6 months following hippocampal-sparing PCI relative to the historical control. Secondary objectives are to estimate: 1) composite cognitive function following hippocampal-sparing PCI relative to the historical control and 2) the rate of metastases in the hippocampus at 2 years following hippocampal-sparing PCI. The long term goal of this research is to reduce the long term sequelae of radiation therapy for both primary and metastatic brain tumors.