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J Clin Pathol 2007;60:1112-1116 doi:10.1136/jcp.2006.044537
  • Original article

Selecting immunohistochemical cut-off scores for novel biomarkers of progression and survival in colorectal cancer

  1. Inti Zlobec1,
  2. Russell Steele2,
  3. Luigi Terracciano3,
  4. Jeremy R Jass1,
  5. Alessandro Lugli1
  1. 1Department of Pathology, McGill University, Montreal, Québec, Canada
  2. 2Department of Mathematics and Statistics, McGill University, Montreal, Québec, Canada
  3. 3Institute of Pathology, University Hospital of Basel, Basel, Switzerland
  1. Ms Inti Zlobec, Department of Pathology, McGill University, Duff Medical Building, Room B22, 3775 University Street, H3A 2B4 Montreal, Québec, Canada; inti.zlobec{at}elf.mcgill.ca
  • Accepted 6 December 2006
  • Published Online First 20 December 2006

Abstract

Background: Cut-off scores for determining positivity of biomarkers detected by immunohistochemistry are often set arbitrarily and vary between reports.

Aims: To evaluate the performance of receiver operating characteristic (ROC) curve analysis in determining clinically important cut-off scores for a novel tumour marker, the receptor for hyaluronic acid mediated motility (RHAMM), and show the reproducibility of the selected cut-off scores in 1197 mismatch-repair (MMR) proficient colorectal cancers (CRC).

Methods: Immunohistochemistry for RHAMM was performed using a tissue microarray of 1197 MMR-proficient CRC. Immunoreactivity was scored using a semi-quantitative scoring method by evaluating the percentage of positive tumour cells. ROC curve analysis was performed for T stage, N stage, tumour grade, vascular invasion and survival. The score with the shortest distance from the curve to the point with both maximum sensitivity and specificity, i.e. the point (0.0, 1.0), was selected as the cut-off score leading to the greatest number of tumours correctly classified as having or not having the clinical outcome. In order to determine the reliability of the selected cut-off scores, 100 bootstrapped replications were performed to resample the data.

Results: The cut-off score for T stage, N stage, tumour grade and vascular invasion was 100% and that for survival 90%. The most frequently selected cut-off score from the 100 resamples was also 100% for T stage, N stage, tumour grade, and vascular invasion and 90% for survival.

Conclusions: ROC curve analysis can be used as an alternative method in the selection and validation of cut-off scores for determining the clinically relevant threshold for immunohistochemical tumour positivity.

Footnotes

  • Competing interests: None declared.

  • Funding: This study was supported by the Faculty of Medicine, McGill University, by a grant from the Swiss National Foundation (grant no PBBSB-110417) and the Novartis Foundation, formerly Ciba-Geigy-Jubilee-Foundation.

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