What if a blood test or biopsy could predict if a cancer therapy will help cure you, or only make you feel worse?

Tests like these, based on genes, proteins or other "molecular markers" may someday do just that for people battling colon, lung and pancreatic tumors, scientists reported at a news conference.

"The ultimate goal is to bring personalized medicine to reality, to identify characteristics of tumors or patients where we can make a relatively dramatic impact using targeted agents," said Dr. Bruce Johnson of the Dana-Farber Cancer Institute and Harvard Medical School, in Boston.