Siteman Cancer Center’s cutting-edge facilities and nationally renowned staff would be nothing without the people who lead them. Our leadership team is comprised of doctors, some of whom have been with Siteman since its inception in 1999, who are committed to serving as a resource through ever phase of the cancer journey.


Timothy Eberlein, MD

John DiPersio, MD, PhD
Deputy Director

Graham Colditz, MD, DrPH
Associate Director, Prevention and Control

Nick Fisher, MBA
Executive Director of Research & Business Administration

Jeff Michalski, MD, MBA
Medical Director, Clinical Trials

Karen Seibert, PhD
Associate Director, Shared Resources

Sheila Stewart, PhD
Associate Director, Basic Science

Sam Achilefu, PhD
Co-Leader: Oncologic Imaging Program

Farrokh Dehdashti, MD
Co-Leader: Oncologic Imaging Program

Dennis Hallahan, MD
Professor and Chair of Radiation Oncology

Christina Longnecker, JD, MBA, BSN, RN
Vice President of Oncology Services

Daniel Link, MD
Co-Leader: Hematopoietic Development & Malignancy Program; PI – Leukemia SPORE

William Hawkins, MD
PI – Pancreatic SPORE

Lee Ratner, MD, PhD
Co-Leader: Solid Tumor Therapeutics Program