Comparing L-arginine by vein and by mouth with whole-brain radiation for brain metastases

This early phase I trial evaluates different administration techniques (oral or intravenous) for arginine and tests the safety of giving arginine with whole brain radiation therapy in patients who have cancer that has spread from where it first started (primary site) to the brain (brain metastases). Arginine is an essential amino acid. Amino acids are the molecules that join together to form proteins in the body. Arginine supplementation has been shown to improve how brain metastases respond to radiation therapy. The optimal dosing of arginine for this purpose has not been determined. This study measures the level of arginine in the blood with oral and intravenous dosing at specific time intervals before and after drug administration to determine the best dosing strategy.