title: Analysis of Prognostic Factors from 9387 Merkel Cell Carcinoma Cases Forms the Basis for the New 8th Edition AJCC Staging System.
abstract: The first consensus Merkel cell carcinoma (MCC) staging system was published in 2010. New information on the clinical course prompts review of MCC staging.
  
  
  
  A total of 9387 MCC cases from the National Cancer Data Base Participant User File with follow-up and staging data (1998-2012) were analyzed. Prognostic differences based on clinical and pathological staging were evaluated. Survival estimates were compared by disease extent.
  
  
  
  Sixty-five percent of cases presented with local disease, whereas 26 and 8 % presented with nodal and distant disease. Disease extent at presentation was predictive of 5-year overall survival (OS) with estimates of 51, 35, and 14 % for local, nodal, and distant disease. Tumor burden at the regional nodal basin was predictive of 5-year OS with estimates of 40 and 27 % for clinically occult and clinically detected nodal disease. For local disease, we confirm improved prognosis when the regional nodal basin was negative by pathological compared with clinical staging. We identified 336 cases with clinically detected nodal disease and unknown primary tumor and showed improved prognosis over cases presenting with concurrent primary tumor (OS estimates of 42 vs. 27 %).
  
  
  
  Analysis of a national dataset of MCC cases validates the predictive value of disease extent at presentation. Separation of clinical and pathological stage groups and regrouping of unknown primary tumors are supported by the analysis. The revised staging system provides more accurate prognostication and has been formally accepted by the AJCC staging committee for inclusion in the 8th edition.
authors.affiliation: Department of Dermatology, University of Michigan Health System and Medical School, Ann Arbor, MI, USA. kharms@med.umich.edu.
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Harms
authors.affiliation: Department of Surgery, University of Michigan Health System and Medical School, Ann Arbor, MI, USA.|Center for Healthcare Outcomes & Policy, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Healy
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, WA, USA.|Fred Hutchinson Cancer Research Center, Seattle, WA, USA.|Seattle Cancer Care Alliance, Seattle, WA, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Nghiem
authors.affiliation: Department of Dermatology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Sober
authors.affiliation: Department of Dermatology, University of Michigan Health System and Medical School, Ann Arbor, MI, USA.|Department of Surgery, University of Michigan Health System and Medical School, Ann Arbor, MI, USA.|Department of Otolaryngology, University of Michigan Health System and Medical School, Ann Arbor, MI, USA.
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Johnson
authors.affiliation: Department of Dermatology, University of Michigan Health System and Medical School, Ann Arbor, MI, USA.
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Bichakjian
authors.affiliation: Department of Surgery, University of Michigan Health System and Medical School, Ann Arbor, MI, USA.|Center for Healthcare Outcomes & Policy, University of Michigan, Ann Arbor, MI, USA.|Department of Surgery, Dartmouth-Hitchcock Medical Center and Geisel School of Medicine at Dartmouth, Lebanon, NH, USA.
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Wong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015266:Carcinoma, Merkel Cell / Q000556:secondary*; D016208:Databases, Factual; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods*; D009382:Neoplasms, Unknown Primary / Q000473:pathology*; D011379:Prognosis; D012878:Skin Neoplasms / Q000473:pathology*; D015996:Survival Rate