Sarah Iselin, President and CEO of Blue Cross Blue Shield of Massachusetts, keynoted the March 14 AIM Executive Forum at Alkermes in Waltham. Ms. Iselin, in conversation with AIM President and CEO Brooke Thomson, shared insights on escalating health care costs and the challenges facing the health-care delivery system in Massachusetts. She also discussed what businesses, providers and policymakers can do to help flatten costs and keep the health-care ecosystem thriving and strong: Massachusetts must  provide world leading health care solutions, while keeping costs manageable.