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Physicians & Staff

Zafer Yildirim, MD, PhD, ABIM

Yildirim, MD, PhD, ABIM specializes in medical oncology and hematology. He brings high quality, comprehensive cancer care to patients in the Lower Columbia Region. Dr. Yildirim is board certified by the American Board of Internal Medicine in Hematology/Oncology and Internal Medicine. His specialized training and background will serve the patients of the Lower Columbia Region well.

Dr. Yildirim has spent over 14 years completing his post-graduate studies at prestigious universities and medical schools throughout the United States:

  • PhD: 1990-1996
    Case Western Reserve University in Cleveland, Ohio
  • Internal Medicine Residency: 1996-1999
    Michigan State University College of Human Medicine/Spectrum Health in Grand Rapids, Michigan
  • Critical Care Fellowship: 1999-2000
    St. Louis University/St. John's Mercy Medical Center in St. Louis, Missouri
  • Hematology/Medical Oncology Fellowship:2000-2003
    University of Vermont/Fletcher Allen Health Care in Burlington, Vermont

According to Dr. Hyman Muss, Director of Hematology/Oncology Fletcher Allen Health Care in Burlington, Vermont, "Dr. Yildirim personifies all those qualities one desires in a hematologist/oncologist- compassion and dedication to patient care and caring, excellence, and cutting-edge knowledge."

Robert A. Joseph, MD

Robert A. Joseph, MD specializes in oncology, hematology, and internal medicine.  He is a member of both the American College of Physicians and the American Society of Clinical Oncology, and is Board Certified as a Diplomate of the American Board of Internal Medicine, and as a Diplomate in Clinical Oncology.   Dr. Joseph's medical career includes work with the US Army Medical Corps, the UCLA Medical Center, Cedars/Sinai Medical Center, Westlake Community Hospital. Los Robles Regional Medical Center, Simi Valley Adventist Hospital, and Pleasant Valley Hospital.

Dr. Joseph is a graduate of Purdue University (Science) and the University of Illinois School of Medicine.  He performed a medical internship in Los Angeles County, followed by residency at Wadsworth VA/UCLA Medical Centers (Internal Medicine, Hematology) and USC Medical Center (Oncology).

Dr. Joseph spent more than 30 years in private practice in Westlake Village, CA before coming to PeaceHealth St. John Medical Center.

Stephanie Roberts, BS, MPAS, PA-C

Stephanie Roberts is a board certified Physician Assistant working at the Lower Columbia Regional Cancer Center.

She is originally from Ohio. She moved to the Pacific Northwest in 2004 to enjoy the lifestyle and outdoor activities of the region. 

Stephanie has worked in Oncology since becoming a PA and finds it a very rewarding field. She is also trained as a genetics educator and can work with patients regarding their cancer risk.

Education and Training:

  • College: The Ohio State University, BS, Zoology 1996
  • Medical School: University of Florida Physician Assistant program, MPAS 2001
  • Hospital Staff Appointments: St. John Medical Center, Longview

Karla Houk, RN, BSN, OCN

Karla Houk is Manager of the PeaceHealth Lower Columbia Cancer Center.  

Karla is an experienced and knowledgeable oncology nurse and has functioned in a variety of capacities as an oncology nurse in her 20-year span of nursing.  Karla grew up in eastern Washington, graduated from Pacific Lutheran University with a Bachelors of Science in Nursing degree.  She is an Oncology Certified Nurse, Chemotherapy Certified Nurse and has served as an educator for the American Cancer Society.

Brandi Crape

Brandi Crape is the Patient Care Coordinator at the PeaceHealth Lower Columbia Cancer Center.  The role of the patient care Coordinator is to help, support and guide patients and families through the maze of issues they encounter during their cancer experience.