For the past four years, Pennsylvania insurance company Highmark has watched its bills for cancer care skyrocket. The increase wasn't because of new drugs being prescribed or a spike in diagnoses. Instead, the culprit was a change that had nothing to do with care: Previously independent oncology clinics and private practices have been acquired by big hospital systems that charge higher rates, sometimes three times as much, for chemotherapy drugs. As the Affordable Care Act attempts to steer people away from pricey inpatient admissions, hospitals have begun buying up doctors' offices in hopes of increasing their revenue and market share.