Radiation regimens for PCI that have influenced patterns of CNS failures in NSCLC have included total doses of 20-36 Gy and fraction sizes of 2-3 Gy. A fraction size of 2 Gy and a total dose of 30 Gy was chosen for the RTOG 0214 study of PCI in LA-NSCLC. This regimen has been shown to decrease CNS metastases from 54% to 13% with no difference in NCF decline in PCI versus non-PCI patients at 4 years. In addition, although there is paucity of clinical data from WBRT with doses in the EQD2 (equivalent dose in 2 Gy fractions) range of 10-20 Gy, a dose-response curve providing a 'best fit' model suggests an only minimal benefit from doses above 30 Gy (EQD2).