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Dennis J. Ahnen, MD

Professor of Medicine

Professor of Medicine


  • Undergraduate: Florida State University, Tallahassee, FL, 1964-1969
  • Medical School: Wayne State University, Detroit, MI 1969-1973
  • Internship/Residency: Hutzel Hospital, Detroit Medical Center, Detroit, MI 1973-1977
  • Fellowship: Gastroenterology University of Colorado Denver 1977-1980
  • Fellowship: Membrane Pathobiology, Stanford University, 1980-1982
  • Board Certified in Internal Medicine and Gastroenterology

Honors and Awards

  • NIH Clinical Investigator Award
  • Veterans Administration Research Associate Award
  • Veterans Administration Clinical Investigator Award
  • University of Colorado Cancer Center Award for Cancer Prevention and Control Research

Faculty Appointments

  • Denver VA Medical Center and University of Colorado Denver, 1981-present


  • Eastern Colorado Health Care System Cancer Committee, Member - 2007- present 
  • Department of Veterans Affairs Cooperative Studies Program CSP #380 "Propective Evaluation of Risk Factors for Colonic Malignancy In Asymptomatic Subjects." Executive Committee - 1993-present
  • American Cancer Society Colorectal Cancer Task Force - 2000-present
  • Colorado Colorectal Cancer Screening Guidelines Collaborative - 2000-present
  • VA Cooperative Studies Program #570 - Colorectal Cancer Screening Trial Planning Committee - 2008-present
  • Colorectal Cancer Family Registry
    • Steering Committee - 2010-present
    • Translational Working Group - 2008-present
    • Behavioral Working Group - 2008-present
  • American Gastroenterological Association
    • Research Committee - 2008-2011
    • Research and Publications Committee - 2011-present
    • Digestive Health Outcomes Registry - 2011-present

    Research Interests

    At the basic level the Ahnen Lab is examining the biologic and the biochemical mechanisms of the chemopreventive effects of the non-steroidal anti-inflammatory drugs (NSAIDs). The lab is currently examining the effect of NSAIDs on EGF receptor expression and function. Dr. Ahnen collaborates closely with the laboratory group of Pamela Rice, PhD a faculty member in the Division on this basic science work.
    Dr. Ahnen's clinical trials group participates in several colorectal cancer prevention trials including several adenoma chemoprevention trials. Dr. Ahnen also collaborates with Al Marcus PhD and staff at the AMC Cancer Research Center to evaluate behavioral interventions to increase colorectal cancer screening rates in high-risk populations and he directs the Colorado site for two national cancer registries that identify high risk families for genetic and clinical trials.

    Representative Publications

    1. Rice PL, Peters S, Beard KS, Ahnen DJ. Sulindac independently modulates extracellular signal-regulated kinase 1/2 and cyclic GMP-dependent protein kinase signaling pathways. Mol Cancer Ther. 5:746-54, 2006. (click here for pdf)

    2. Denberg TD, Coombes JM, Byers TE, Marcus AC, Feinberg LE, Steiner JF, Ahnen DJ. Effect of a mailed brochure on appointment-keeping for screening colonoscopy: a randomized trial. Ann Intern Med. 145:895-900, 2006. (click here for pdf)

    3. Cole BF, Baron JA,. Sandler RS, Haile RW, Ahnen DJ, Bresalier RS, McKeown-Eyssen G, Summers RW, Rothstein RI, Burke CA, Snover DC, Church TR, Allen JI, Robertson DJ, Beck GJ, Bond JH, Byers T, Mandel JS, Mott LA, Pearson LH, Barry EL, Rees JR, Marcon N, Saibil F, Ueland PM, Greenberg ER, For the Polyp Prevention Study Group. Folic acid for the prevention of colorectal adenomas: a randomized clinical trial. JAMA 297:2351-9, 2007 (click here for pdf)

    4. Ahnen DJ, Guerciolini R, Hauptman J, Blotner S, Woods CJ, Whittington J, Wargovich MJ. Effect of orlistat on fecal fat, fecal biliary acids and colonic cell proliferation in obese subjects. Clinical Gastroenterology and Hepatology 5:1291-9, 2007

    5. Debourcy AC, Lichtenberger S, Felton S, Butterfield KT, Ahnen DJ, Denberg TD. Community-based preferences for stool cards versus colonoscopy in colorectal cancer screening. J Gen Intern Med. 23:169-74, 2008. (click here for pdf)

    6. Meyskens FL, McLaren CE, Pelot D, Fujikawa-Brooks S, Carpenter PM, Hawk E, Kelloff G, Lawson MJ, Kidao J, McCracken J, Albers CG, Ahnen DJ, Turgeon DK, Goldschmid S, Lance P, Hagedorn CH, Gillen DL, Gerner EW. Difluoromethylornithine plus sulindac for the prevention of sporadic colorectal adenomas: a randomized placebo-controlled, double-blind trial. Cancer Prevention Research 1:9-11, 2008 (click here for pdf)

    7. Ahlquist DA, Sargent DJ, Loprinzi CL, Levin TR, Rex DK, Ahnen DJ, Knigge K,, M. Lance MP, Burgart LJ, Hamilton SR,Allison JE,Lawson MJ, Devens ME, Harrington JJ, Hillman SL. Stool DNA and occult blood testing for screen-detection of colorectal neoplasia: a prospective multi-center comparison. Ann Intern Med;149:441-450, 2008. (click here for pdf)

    8. Zou H, Taylor WR, Harrington JJ, Hussain FT, Cao X, Loprinzi CL, Levine TR, Rex DK, Ahnen D, Knigge KL, Lance P, Jiang X, Smith DI, Ahlquist DA. High detection rates of colorectal neoplasia by stool DNA testing with a novel digital melt curve assay. Gastroenterology. 136:459-70, 2009 (click here for pdf)

    9. Grau MV, Sandler RS, McKeown-Eyssen G, Bresalier RS, Haile RW, Barry EL, Ahnen DJ, Gui J, Summers RW, Baron JA. Nonsteroidal anti-inflammatory drug use after 3 years of aspirin use and colorectal adenoma risk: observational follow-up of a randomized study. J Natl Cancer Inst. 101:267-76, 2009 (click here for pdf)

    10. Martínez ME, Baron JA, Lieberman DA, Schatzkin A, Lanza E, Winawer SJ, Zauber AG, Jiang R, Ahnen DJ, Bond JH, Church TR, Robertson DJ, Smith-Warner SA, Jacobs ET, Alberts DS, Greenberg ER. A pooled analysis of advanced colorectal neoplasia diagnoses after colonoscopic polypectomy. Gastroenterology 136:832-41, 2009 (click here for pdf)

    11. Wallace K, Grau MV, Ahnen D, Snover DC, Robertson DJ, Mahnke D, Gui J, Barry EL, Summers RW, McKeown-Eyssen G, Haile RW, Baron JA. The association of lifestyle and dietary factors with the risk for serrated polyps of the colorectum. Cancer Epidemiol Biomarkers Prev. 18:2310-7, 2009 (click here for pdf)

    12. Pangburn H, Ahnen DJ, Rice PL. Sulindac metabolites induce proteosomal and lysosomal degradation of the epidermal growth factor receptor. In press, Cancer Prevention Research