title: Analytic lymph node number establishes staging accuracy by occult tumor burden in colorectal cancer.
abstract: OBJECTIVE
  Recurrence in lymph node-negative (pN0) colorectal cancer suggests the presence of undetected occult metastases. Occult tumor burden in nodes estimated by GUCY2C RT-qPCR predicts risk of disease recurrence. This study explored the impact of the number of nodes analyzed by RT-qPCR (analytic) on the prognostic utility of occult tumor burden.
  
  
  METHODS
  Lymph nodes (range: 2-159) from 282 prospectively enrolled pN0 colorectal cancer patients, followed for a median of 24 months (range: 2-63), were analyzed by GUCY2C RT-qPCR. Prognostic risk categorization defined using occult tumor burden was the primary outcome measure. Association of prognostic variables and risk category were defined by multivariable polytomous and semi-parametric polytomous logistic regression.
  
  
  RESULTS
  Occult tumor burden stratified this pN0 cohort into categories of low (60%; recurrence rate (RR) = 2.3% [95% CI 0.1-4.5%]), intermediate (31%; RR = 33.3% [23.7-44.1%]), and high (9%; RR = 68.0% [46.5-85.1%], P < 0.001) risk of recurrence. Beyond race and T stage, the number of analytic nodes was an independent marker of risk category (P < 0.001). When >12 nodes were analyzed, occult tumor burden almost completely resolved prognostic risk classification of pN0 patients.
  
  
  CONCLUSIONS
  The prognostic utility of occult tumor burden assessed by GUCY2C RT-qPCR is dependent on the number of analytic lymph nodes.
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Terry
authors.initials: T
authors.lastname: Hyslop
authors.forename: David S
authors.initials: DS
authors.lastname: Weinberg
authors.forename: Stephanie
authors.initials: S
authors.lastname: Schulz
authors.forename: Alan
authors.initials: A
authors.lastname: Barkun
authors.forename: Scott A
authors.initials: SA
authors.lastname: Waldman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000473:pathology*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis; D009367:Neoplasm Staging; D009382:Neoplasms, Unknown Primary / Q000473:pathology*; D016017:Odds Ratio; D016133:Polymerase Chain Reaction / Q000379:methods; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D047368:Tumor Burden