Bloomberg -- Doctors who perform robotic-assisted prostate cancer surgery aren’t proficient and able to remove all the malignant cells surrounding the tumor until they have done the procedure more than 1,600 times, researchers said. Results from a study suggest the operations using Intuitive Surgical Inc.’s da Vinci robot are being performed too often at community hospitals by surgeons without enough experience, said Prasanna Sooriakumaran, lead author and urologist at the Weill Cornell Medical College in New York.