title: Clinical utility of a circulating tumor cell assay in Merkel cell carcinoma.
abstract: BACKGROUND
  Quantitation of circulating tumor cells (CTCs) has utility in managing breast, colon, and prostate carcinomas.
  
  
  OBJECTIVE
  We sought to determine whether a commercially available CTC assay provides prognostic information in Merkel cell carcinoma (MCC), insight into treatment responses, or both.
  
  
  METHODS
  We analyzed CTCs in 52 specimens from 34 patients with MCC.
  
  
  RESULTS
  The presence of CTCs correlated with extent of disease at blood draw (P = .004). Among 15 patients with regional nodal disease, CTC-negative patients had 80% disease-specific survival at 2 years after the test, versus 29% for CTC-positive patients (P = .015). Among the entire cohort, those without CTCs had 72% MCC-specific survival whereas CTC-positive patients had 25% survival (n = 34, median follow-up 19 months, P = .0003). Fifty seven percent of patients with MCC had a cytokeratin "dot" visible in 20% or more of CTCs, a feature that was absent among CTCs from other carcinomas (0 of 13 cases).
  
  
  CONCLUSIONS
  CTC assay was performed at variable times after diagnosis and heterogeneity in extent of disease affects interpretability of the data.
  
  
  CONCLUSIONS
  CTC detection in MCC is feasible and appears to add prognostic information, particularly in patients with regional nodal disease. It may also assist clinical management in certain situations, including differentiating metastatic MCC cells from those of other carcinomas.
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Astrid
authors.initials: A
authors.lastname: Blom
authors.affiliation: Department of Medicine/Oncology, University of Washington, Seattle, Washington.
authors.forename: Shailender
authors.initials: S
authors.lastname: Bhatia
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Pietromonaco
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, Washington.
authors.forename: Karen
authors.initials: K
authors.lastname: Koehler
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Jayasri G
authors.initials: JG
authors.lastname: Iyer
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Nagase
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Kelly
authors.initials: K
authors.lastname: Paulson
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, Washington.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Sabath
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington. Electronic address: pnghiem@uw.edu.
authors.forename: Paul
authors.initials: P
authors.lastname: Nghiem
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D015415:Biomarkers; D015266:Carcinoma, Merkel Cell / Q000097:blood / Q000401:mortality* / Q000473:pathology*; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D007633:Keratins / Q000032:analysis / Q000378:metabolism; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009364:Neoplasm Recurrence, Local / Q000401:mortality* / Q000473:pathology; D009367:Neoplasm Staging; D009360:Neoplastic Cells, Circulating / Q000473:pathology*; D011379:Prognosis; D018570:Risk Assessment; D012878:Skin Neoplasms / Q000097:blood / Q000401:mortality* / Q000473:pathology*; D018709:Statistics, Nonparametric; D016019:Survival Analysis
chemical_list: D015415:Biomarkers; D007633:Keratins
keywords: Merkel cell carcinoma; biomarker; circulating tumor cells; dot-like cytokeratin; neuroendocrine carcinoma of the skin; prognosis