APAO Board of Directors


Colleen Tetzlaff, PA-C

Colleen Hogan Tetzlaff, MHS, PA-C is a member of the 2004 class of the Duke University PA Program after previously receiving her BSN from Villanova University in 1996.  Colleen has worked in oncology since graduating from PA school. 

Colleen’s PA career started at the UT MD Anderson Cancer Center where she focused on caring for patients with cancers of the lung and head and neck.  While at MD Anderson, Colleen founded and directed the Thoracic Oncology Education Series, served as a clinical preceptor for PA students, and participated in the MD Anderson Ambassador program. 

 After four years at MD Anderson Cancer Center, Colleen relocated to Philadelphia in 2008 and has worked at the Fox Chase Cancer Center since that time.  At Fox Chase, Colleen’s clinical focus is on cancers of the genitourinary tract.  Colleen has been active in representing the PA profession at Fox Chase where she is currently serving as Chairperson of the Advanced Practice Clinician (APC) professional development committee and is a member of the patient education committee.  She has also served as the PA representative to the APC committee and chairperson for the APC recognition working group.  Colleen has an interest in education serving as a clinical preceptor as well as lecturing on the management of treatment related adverse effects for patients with GU malignancies. 

When not at work, Colleen loves to spend time with her family, loves gardening, and is an avid Villanova basketball fan. 

Email Me with any questions. 


Bruce Christensen, PA-C

Bruce Christensen graduated from the United States Air Force/University of Nebraska PA Program with a BS in PA Studies in 1992. He went on to graduate with his Masters in PA studies, with a specialization in Oncology in 1997 from the University of Nebraska.  He also received his Doctorate in Health Sciences, with an emphasis in Leadership and Organizational Behavior in 2012 from A.T. Still University. He has served in the military has practiced in many different areas including internal medicine, hematology/oncology, bone marrow transplant and aerospace physiology. Upon retiring from the military  in 2007, he taught in PA education for 6 years.  He returned to clinical practice and joined the Mays Cancer Center, UT Health San Antonio in April 2013, where he is the senior PA and  specializes in malignant hematology. Christensen has also served on the Board of Directors of the Texas Academy of Physician Assistants for 5 years and just finished his year as Immediate Past President.  He is a Distinguished Fellow of the American Academy of Physician Assistants as well. He currently  is a student preceptor and part time Clinical Assistant Professor with the UT Health Science Center San Antonio PA Program.

Email me with any questions. 

 Past President

Cory Williams, PA-C


Cory Williams is a graduate of Carthage College (2012) where she received a B.S. in Biology with a minor in Chemistry and also played basketball for four years. She then went on to receive her M.S. in Physician Assistant Studies at New York Institute of Technology in 2015. Upon graduation Cory worked at Weill Cornell Medical Center-New York Presbyterian Hospital on the inpatient hematology/oncology floor in New York before moving to Chicago in 2017. She now works in the outpatient lymphoma department at Northwestern Memorial Hospital. Cory has previously served as membership chair (2016-2018), secretary (2017-2018), president-elect (2018-2019) and president (2019-2020) of  APAO.

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Christina DiBenedetto, PA-C

Christina DiBenedetto, PA-C, is a graduate of Quinnipiac University (2008) where she received her B.S. in Biomedical Science with a minor in Psychology.  She then went on to receive her M.S. in Physician Assistant studies at Mercy College in 2010. Christina has worked in oncology since graduating from PA school.  

Christina’s PA career started at Montefiore Medical Center where she focused on caring for patients with gastrointestinal (GI) malignancies. During her 8 years at Montefiore, Christina expanded her knowledge base extensively working with patients with various GI malignancies managing them on standard chemotherapy regimens, immunotherapy, and oral agents as well as treating and enrolling patients in clinical trials. In addition to caring for patients, Christina had taken on other roles at Montefiore including managing the hepatobiliary tumor boards, serving as a member of the quality improvement task force and serving as a member of Montefiore’s Institutional Review Board.  

Christina recently accepted and started an advanced practice provider position at Memorial Sloan Kettering Cancer Center as a member of the gastrointestinal oncology team.

 When not at work, Christina loves to spending time with her husband and their cat Bilbo or spending time in the gym.


Theresa Wittenberg, MS, PA-C

Theresa Wittenberg is a graduate of Baylor College of Medicine and has been a PA-C for over 20 years. She has worked in oncology for 10 of those years at various institutions such as Fred Hutchinson Cancer Research Center, Seattle Cancer Care Alliance, and currently Stanford Health Care.  Her special interests are in gastrointestinal medical oncology, neuroendocrine tumors, and cancer survivorship. In addition to work, Theresa enjoys spending time with her family, reading, baking sourdough bread, and tap dancing. 

She is excited to serve as Treasurer of APAO and to become more involved with APAO to help promote physician assistants in the field of oncology!  

 Email me with any questions. 


Sarah Vitulli, PA-C

Sarah is a graduate of Rutgers University (2010) where she received her undergraduate B.A. degree in Biology with a minor in psychology. She then went on to earn a dual degree, M.S. in Physician Assistant Studies and  B.S. in Health Sciences at Touro College Manhattan (2016).  Sarah also served as her physician assistant class Vice President and also completed additional coursework in a Behavioral Health Program. She has since started her physician assistant career at Weill Cornell Medical Center-New York Presbyterian Hospital on the hematology/oncology inpatient service where she currently works.

Email me with any questions. 


Keara Barnaby, PA-C (Information Coming Soon)

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AAPA House of Delegates and AAPA/APAO Liaison to ASCO

Heather Hylton, PA-C

Heather Hylton, PA-C

Heather Hylton is a graduate of Baylor College of Medicine’s Physician Assistant Program and completed the MD Anderson Cancer Center’s Postgraduate Physician Assistant Program in Oncology. Her clinical background is in hematologic malignancies and stem cell transplantation. She has served in key administrative and clinical roles at leading healthcare facilities, including the Dana-Farber Cancer Institute and Memorial Sloan Kettering Cancer Center. She is a past president of the APAO and is actively involved with the American Society of Clinical Oncology (ASCO) and AAPA. In her free time, Heather is an avid and adventurous traveler.

Email me with any questions. 

AAPA House of Delegates Alternate

Jennifer Reinhart, PA-C

Jennifer Reinhart, PA-C

Jennifer Reinhart has been a practicing PA for the past 7 years. She graduated from Marist College with her B.S in Biology in 2007. She then went on to obtain her MS in advanced physician assistant studies from Wagner College in 2012. Upon graduation she started practicing in general hematology/oncology at Advantage Care Physicians in Staten Island, NY. In 2016 she moved to Mount Sinai Hospital, where she continues to practice today, specializing in Multiple Myeloma and bone marrow biopsies. She sits on the Mount Sinai PA council where she is also a member of the PA mentorship committee and PA volunteer committee. She has been a member of APAO since 2013. She loves to advocate for our profession bringing PAs to the forefront of medicine. In her spare time she enjoys teaching dance and spending time with family and friends.   

Email me with any questions.