Two drugs from Bristol-Myers Squibb (BMY), taken together, shrank tumors in melanoma patients. Tumors shrank in 53% of patients who got the most effective dose of a combination of the company's melanoma drug Yervoy and nivolumab, its experimental treatment that targets the immune system. Bristol-Myers and Roche Holding (RHHBY) are competing on new cancer treatments that use the immune system, a potential multibillion-dollar market. Bristol-Myers shares rose 1.2% to 43.30. Roche 1% to 63.13.