Your Medical Team

Surgeons


Jon Vogel, MD, FACS, FASCRS

Jon Vogel, MD, FACS, FASCRS

Clinic Director, Surgeon

Dr. Vogel received his General Surgery training at the Johns Hopkins Hospital and completed his Colorectal Surgery fellowship at the Cleveland Clinic in 2005. He was an attending colorectal surgeon at the Cleveland Clinic from 2005 to 2013. In 2013 he joined the University of Colorado to lead the Colorectal Surgery program. Dr. Vogel is board certified in general and colorectal surgery. He has extensive experience with laparoscopic colorectal surgical techniques. His research on laparoscopic colorectal surgery has been published in leading surgical journals. (View profile)

Steve Ahrendt, MD, FACS

Steven A. Ahrendt, MD, FACS

Surgeon

Dr. Ahrendt received both his General Surgery and Surgical Oncology training at the Johns Hopkins University. He has been on the faculty of the Johns Hopkins University, the Medical College of Wisconsin, the University of Rochester, and the University of Pittsburgh. He joined the faculty at the University of Colorado in May 2017 and serves as Director of the Cytoreductive Surgery and HIPEC program. He specializes in treating patients with complex gastrointestinal malignancies, including primary and metastatic colon and appendiceal cancer, with an emphasis on peritoneal surface malignancies or carcinomatosis. His research on cytoreductive surgery with intraperitoneal chemotherapy has been published in leading surgical journals. (View profile)

Elise Birnbaum, MD

Elisa H. Birnbaum, MD

Surgeon

Dr. Birnbaum earned her Bachelor of Science at the University of Wisconsin and her MD at the University of Illinois Medical School. She subsequently completed her general surgery residency at Long Island Jewish Medical Center in New York and her Colorectal Surgery fellowship at the Barnes-Jewish Hospital in St. Louis. She served on faculty at Washington University School of Medicine from 1991 to 2017, most recently as Professor of Surgery and Director of the Center for Colorectal and Pelvic Floor Disorders.

Her interests are in the medical and surgical management of pelvic floor abnormalities, particularly fecal incontinence, constipation, and rectal prolapse. She has 25 years of surgical experience and expertise in laparoscopic and robotic approaches to colorectal diseases. She has published numerous papers and chapters on colorectal diseases and is a recent recipient of the faculty mentorship award at Washington University given by the surgical residents. Dr. Birnbaum has been active on ACS and ASCRS committees, as a council member of the ASCRS, and is currently a board member on the ABCRS. At the University of Colorado, she serves as Professor of Surgery and Co-director of the Anorectal Physiology Laboratory. (View profile)

Ana Gleisner, MD, PhD

Ana Gleisner, MD, PhD

Surgeon

Dr. Gleisner received her General Surgery training at the Saint Louis University and completed a fellowship in Surgical Oncology at University of Pittsburgh Medical Center. She specializes in treating gastrointestinal cancers, including primary and metastatic colon and rectal tumors, with emphasis on minimally invasive surgery as well as on tumor debulking and hyperthermic perfusion. She has been with the University of Colorado School of Medicine since 2015 and is board certified in general surgery. Her research interests focus on the comparison of the efficacy of different surgical treatments for cancer being used across the country. (View profile)

Martin McCarter, MD, FACS

Martin McCarter, MD, FACS

Surgeon

Dr. McCarter received his General Surgery training at the New York Hospital Cornell Medical School and completed a fellowship in surgical oncology at Memorial Sloan Kettering in 2001. He specializes in treating complex gastrointestinal cancers, including primary and metastatic colon and rectal tumors. A professor of surgery, he has been with the University of Colorado School of Medicine since 2001 and is board certified in general surgery. His research interests focus on targeted therapies for cancer and the interaction between the immune system and tumors. (View profile)

Brandon C. Chapman, MD, MS

Brandon Chapman, MD, MS

Surgeon

Dr. Chapman received his general surgery training at the University of Colorado School of Medicine and completed his Colorectal Surgery fellowship at the University of Tennessee College of Medicine Chattanooga. During his general surgery residency, he received the J. Culthbert Owens Award for Excellence in Teaching and Patient Care. Additionally, he completed a 2-year surgical research fellowship in clinical outcomes and obtained a Master of Science in Clinical Science at the University of Colorado Denver. Dr. Chapman has published numerous peer-reviewed journal articles and has presented at multiple national meetings across the country. His research interests focus on surgical outcomes and quality improvement, laparoscopic and robotic colorectal surgery, and rectal cancer. He is an active participant in the American Society of Colon and Rectal Surgeons (ASCRS) and currently serves on the Young Surgeons Committee. (View profile)


Medical Oncologists


Martin McCarter, MD, FACS

S. Lindsey Davis, MD

Medical Oncologist

Dr. Davis completed her internal medicine and medical oncology training at the University of Colorado, and served as Chief Medical Resident and Chief Oncology Fellow in these programs. She is a member of the Gastrointestinal Medical Oncology Program as well as the Developmental Therapeutics Program at the University of Colorado. Her research interest is in novel targeted therapies and immunotherapies for colorectal cancer.

Stephen Leong, MD

Stephen Leong, MD

Medical Oncologist

Dr. Leong received his medical training at the Royal College of Surgeons in Ireland and Albert Einstein Medical Center in Philadelphia. He then trained in medical oncology at the University of Colorado Cancer Center. He joined the UCH faculty in 2007. He is a member of the Gastrointestinal Malignancies and Developmental Therapeutic Programs, where he conducts research and clinical trials in colorectal cancer.

Christopher Lieu, MD

Christopher Lieu, MD

Medical Oncologist

Dr. Lieu joined the University of Colorado School of Medicine faculty as an Assistant Professor of Medicine in July 2011. He trained in internal medicine at the University of Colorado, where he also served as a Chief Medical Resident. He completed his fellowship training in medical oncology at the University of Texas MD Anderson Cancer Center and served as the Chief Medical Oncology Fellow in 2010. He currently serves as the Director of GI Medical Oncology at the University of Colorado Cancer Center, is a member of the National Cancer Institute Colon Cancer Task Force, and serves on the National Comprehensive Cancer Network (NCCN) Panel for Neuroendocrine Cancers.

Wells Messersmith, MD

Wells Messersmith, MD

Medical Oncologist

Dr. Messersmith trained at Harvard Medical School and Johns Hopkins. He joined the UCH faculty in 2007. Dr. Messersmith conducts both local and national translational clinical trials in cancers of the pancreas, colon, liver, and gastrointestinal tract. He serves as Head of the Division of Medical Oncology and co-Leader of Developmental Therapeutics at the University of Colorado Cancer Center.

W. Thomas Purcell, MD, MBA

W. Thomas Purcell, MD, MBA

Medical Oncologist

Dr. Purcell trained in Internal Medicine and Medical Oncology at the Emory University School of Medicine, followed by residency training at University of Texas Southwestern Medical Center/Parkland Hospital in Dallas, Texas. He then completed fellowship training in Medical Oncology at Johns Hopkins Sidney Kimmel Comprehensive Cancer Center in Baltimore, Maryland. Dr. Purcell joined the faculty of the University of Colorado in May of 2012. He is currently the Executive Medical Director of Oncology Services and Associate Director for Clinical Services at the University of Colorado Cancer Center.


Radiation Oncologist


Tracey E. Schefter, MD

Tracey E. Schefter, MD

Radiation Oncologist

Dr. Schefter is board certified in radiation oncology in both Canada and the U.S. She received her medical degree from Queen's University in Kingston, Ontario, Canada (1990-1994) and completed her residency training in radiation oncology at the Princess Margaret Hospital in Toronto, Canada (1994-1999). She completed a one-year fellowship at MD Anderson Cancer Center (1999-2000). She is the principal investigator on numerous clinical trials, has contributed to more than 50 publications, and currently serves on several national committees.


Gastroenterologist


Swati Patel, MD, MS

Swati Patel, MD, MS

Gastroenterologist

Dr. Patel completed a Masters in Health Systems Administration from Union University and attended Albany Medical College for her medical degree. She completed her Internal Medicine Residency and Gastroenterology fellowship at the University of Colorado. She is board certified in Internal Medicine and Gastroenterology. She was on faculty at the University of Michigan from 2013 to 2015 and joined the University of Colorado in 2015. She is the Director of the Gastrointestinal Cancer Risk and Prevention Clinic at the Anschutz Medical Center, where she cares for patients at high risk for cancer based on their family history and genetics. Her clinical and research interests are in colorectal cancer prevention, identification and management of patients at high risk for colorectal cancer, and colonoscopy quality and training.


Physician Assistant


Shanna Zwick, PA-C

Shanna Zwick, PA-C, MS

Shanna earned her Master of Medical Science from Saint Louis University’s Physician Assistant program in 2012. Prior to re-locating to Colorado in 2017, she spent her time in Colorectal Surgery at Washington University in St. Louis, MO. She joined the University of Colorado in 2018 with the Department of Interventional Radiology prior to transitioning to Colorectal Surgery. She has extensive knowledge in multiple areas within the colorectal specialty and sees patients in both the hospital and outpatient settings. Her dedication to colorectal surgery is defined by the compassion she provides to patients regarding a subject matter that can often be sensitive in nature. (View profile)


Multidisciplinary Clinic Coordinator


Whitney Herter, PA-C

Whitney Herter, PA-C

As research for the treatment of colorectal cancer develops, fewer patients are being treated with single-modality therapy. Instead, most patients are being treated with a combination of surgery, chemotherapy and/or radiation therapy. This often makes navigating the healthcare system difficult and overwhelming. In a traditional medical environment, patients are often seen by different specialists over the course of several weeks. The Colorectal Cancer Multidisciplinary Clinic is designed so that patients are seen by our team of specialists over one day with the goal of having a treatment plan by the end of the visit.

In order to make this process easier for you, I am your point person from the start. This means from your initial phone call throughout your entire visit, I am by your side. As a certified Physician Assistant, I have the medical knowledge to effectively guide your treatment and get you seen quickly by our multidisciplinary team of experts. This multidisciplinary approach to care provides patients with the most up-to-date and evidence-based treatment to provide the best care for the highest chance of success and cure of disease. (View profile)