On Feb. 3, Joyce Elkins filled a prescription for a two-week supply of nitrogen mustard . . . The cost was $77.50. On Feb. 17, Ms. Elkins, a 64-year-old retiree . . . returned to her pharmacy for a refill. This time . . . the cost was $548.01. Ms. Elkins's insurance does not cover nitrogen mustard, which she must take for at least the next six months at a cost that will now total nearly $7,000. She and her husband . . . are paying for the medicine by spending less on utilities and food, she said. The medicine...