In the latest example of how healthcare companies are joining forces en masse, Franklin-based Iasis Healthcare announced today a joint venture with Aurora Health Care to build a new cancer center in Wisconsin, among other projects. Aurora, a not-for-profit healthcare provider serving communities throughout eastern Wisconsin and northern Illinois, and IASIS also are exploring a variety of other affiliations, including sharing clinical practices. Iasis, the nation's largest privately held hospital company, believes the partnership will give the company the type of scale and expertise needed to succeed amid dwindling federal reimbursement rates.