U.S. regulatory staff raised questions on Wednesday about the safety and effectiveness of Advanced Magnetics Inc.'s experimental imaging agent Combidex. Food and Drug Administration reviewers said they had questions about the validity of findings showing Combidex could help doctors identify cancerous lymph nodes. The FDA staff also said "we cannot rule out the possibility of hypersensitivity-related deaths with Combidex" after one patient in a study died after being injected with the product. Cytogen Corp. has U.S. marketing rights for the product, which will be reviewed by an FDA advisory committee on Thursday. --SP 2113 Local Time 1813 GMT