Enlarge ImageBlocked. Chemo drugs (green) can't penetrate a pancreatic tumor (blue). White stroma (insert) separates blood flow from tumor cells (light brown).Credit: Stefanie Reichelt, Michal Al Jacobetz, and Kenneth P. Olive; (inset) Kenneth P. Olive Almost 95% of pancreatic cancer patients die within 5 years of diagnosis, and traditional chemotherapy does little to save their lives. Now, cancer researchers think they know why--and how they might get around the tumor's defenses. The work "has huge ramifications for how we approach therapy of this disease," says Margaret Tempero, an oncologist at the University of California, San Francisco. Cancers almost always...