Executive Team

LeAnne M. Stewart

Chief Financial Officer

LeAnne Stewart has over two decades of financial management experience in publicly held and private equity sponsored companies.

Prior to joining 21st Century Oncology in 2015, Ms. Stewart served as Chief Financial Officer of CRC Health Group, a private equity sponsored behavioral health organization. She also served as Senior Vice President and Chief Financial Officer at Granite Construction and Nash Finch Company. Ms. Stewart began her career at Ernst & Young where she served a diverse universe of publicly held companies as part of the Assurance group.

Constantine A. Mantz, MD

Chief Medical Officer / Radiation Oncologist

Dr. Constantine “Connie” Mantz joined 21st Century Oncology in 2000 and has served in his current capacity as Chief Medical Officer since February 2011 and formerly as Senior Vice President of Clinical Operations from March 2009 to February 2011. Dr. Mantz is Board Certified in Radiation Oncology by the American Board of Radiology. At 21st Century Oncology, as an area expert, he leads the company’s focus on the study and treatment of prostate and breast cancer.

Eduardo Fernandez, MD, PhD, FACRO, FASTRO

Senior Vice President, Medical Affairs / Medical Director for Latin America / Radiation Oncologist

Dr. Eduardo Fernandez joined 21st Century Oncology in 1998 and has served as the company's Director of Regional Operations and Senior Vice President of Physician Management in the past. In his current role, he is responsible for the oversight and support of the physician, hospital and service provider network strategy. As a Board Certified Radiation Oncologist, Dr. Fernandez also continues to be deeply involved with patient care.

Richard R. Lewis

Senior Vice President / Chief Financial Officer for United States Operations

Mr. Lewis joined 21st Century Oncology in January 2006 and has served in several financial and operational roles including Director of Finance, Regional Director of Operations, and Vice President of Finance Operations. In his current role, Mr. Lewis oversees the company’s domestic financial planning and analysis, risk management and physician administration functions. He is also heavily involved in the company’s business development and physician recruitment as well as the continued development of the company’s business intelligence data warehouse.

Gary Delanois

Senior Vice President, United States Operations

Gary Delanois joined 21st Century Oncology in 2009 and serves as the Senior Vice President of United States Operations. With the goal of creating a seamless approach among multiple care specialties, Mr. Delanois facilitates health care integration to provide comprehensive care toward the best individualized treatment plan and best possible outcome for patients.

Kimberly J. Commins-Tzoumakas

Legal Counsel

Kimberly J. Commins-Tzoumakas has over a decade of experience as outside counsel, providing representation to health care providers, including board governance, general health law, Stark compliance, physician contracting, fraud and abuse, and corporate compliance and regulatory issues.