WILMINGTON, Mass.--(BUSINESS WIRE)--Sirtex, a leading developer of targeted and innovative cancer therapies, is pleased to announce Samuel G. Putnam, M.D. has been named medical director for United States operations. Sirtex manufactures SIR-Spheres® microspheres, the only FDA-approved microsphere therapy for colorectal cancer that metastasizes to the liver.1 Sirtex’s U.S. headquarters are located in Wilmington, Mass.