A Phase II/III Randomized Trial of Two Doses (Phase III-Standard vs. High) and Two High Doe Schedules (Phase II-Once vs. Twice Daily) for Delivering Prophylactic Cranial Irradiation for Patients with Limited Disease Small Cell Lung Cancer

Pts must have histologic proof or unequivocal cytologic proof of SCLC; Pts must have limited disease SCLC, clinical Stages I-IIIB (AJCC, 1997), whatever the induction treatment; Pts must have completed all prescribed chemotherapy 1 week prior to registration and before beginning PCI; Pts must have achieved a complete response to induction chemotherapy (+/- thoracic radiation therapy) according to local habits (at least on a chest X-ray) prior to registration; Pts may have started consolidative chest irradiation prior to registration; Pts must have a Zubrod PS </= 1; Pts must have a normal brain CT scan or MRI < 1 month prior to registration; Pts must have a neurological function Class of 1 or 2 (Appendix II); An Absolute granulocyte count >/= 1,500, HGB >/= 10.0 gm/100 ml and platelet count of >/=75,000 are required; Pts of childbearing potential must practice adequate contraception; A "certified" test administrator (Section 11.4) is required for administration of the neuropsychological tests; Pts must have no radiographic evidence of brain mets; Pts must have no minimal pleural effusion or lung metastases evident on CXR (minimal pleural effusion visible on chest CT is allowed); Pts must not have had prior external beam irradiation to the head or neck; Pts must not have current or past malignancy within the past five years other than non-melanomatous skin cancer or carcinoma in situ of cervix; Pts must not have a serious medical or psychiatric illness that would, in the opinion of the investigator, prevent informed consent, or completion of protocol treatment, and/or follow-up visits; Pts w/epilepsy requiring permanent oral medication are excluded; Pts must not be planning to receive concurrent chemotherapy or antitumoral agents during PCI.