Testing if High Dose Radiation Only to the Sites of Brain Cancer Compared to Whole Brain Radiation That Avoids the Hippocampus is Better at Preventing Loss of Memory and Thinking Ability

Inclusion Criteria: * Pathologically (histologically or cytologically) proven diagnosis of small cell lung cancer within 5 years of registration. If the original histologic proof of malignancy is greater than 5 years, then pathological (i.e., more recent) confirmation is required (e.g., from a systemic or brain metastasis); * Patients with de novo or recurrent small cell lung cancer are permitted. * Brain metastases =\< 4 cm in largest diameter and outside a 5-mm margin around either hippocampus must be visible on contrast-enhanced magnetic resonance imaging (MRI) performed =\< 21 days prior to study entry. * The total tumor volume must be 30 cm\^3 or less. Lesion volume will be approximated by measuring the lesion's three perpendicular diameters on contrast enhanced, T1-weighted MRI and the product of those diameters will be divided by 2 to estimate the lesion volume (e.g. xyz/2). Alternatively, direct volumetric measurements via slice by slice contouring on a treatment planning software package can be used to calculate the total tumor volume. * Brain metastases can be diagnosed synchronous to the initial diagnosis of small cell lung cancer or metachronous to the initial diagnosis and management of small cell lung cancer. * Brain metastases must be diagnosed on MRI, which will include the following elements: * REQUIRED MRI ELEMENTS * Post gadolinium contrast-enhanced T1-weighted three-dimensional (3D) spoiled gradient (SPGR). Acceptable 3D SPGR sequenc…