Policy name changed from "Human Tumor Stem Cell Drug Sensitivity Assay" to "In Vitro Chemoresistance and Chemosensitivity Assays". Reviewed with Senior Medical Director 4/7/09. "Description" section revised. "In vitro chemosensitivity assays, including but not limited to the histoculture drug response assay or a fluorescent cytoprint assay, are considered investigational." "In vitro chemoresistance assays, including but not limited to extreme drug resistance assays are considered investigational." Added CPT code 89240 to "Billing/Coding" section. Notice given 4/27/09. Effective date is 8/3/09.