Dr. Siddhartha Mukherjee became famous with his epic nonfiction book about cancer, “The Emperor of All Maladies.” The book shows that if there’s one constant in cancer research, it’s that it’s always changing. On this episode of “The C-Word: Stories of Cancer,” Shirley talks to Dr. Mukherjee about how his time living and working in Boston changed him as a doctor. They discuss the hopeful progress we’ve made in curing cancer - and the challenges that persist. Email us at saymore@globe.com.