title: Clinical application of tumour markers: a review.
abstract: BACKGROUND
  Tumour markers have made a difference to oncology practice. They can be used in screening, diagnosis, prognostication and assessment of treatment efficacy. Reports on tumour marker usage suggest that many clinicians assume that a biomarker for a particular cancer can be effectively used for all these indications. This assumption is incorrect. Several guidelines have been published to inform clinicians on effective utilisation of these tests.
  
  
  OBJECTIVE
  To outline the recommended uses of the most commonly requested tumours markers in clinical practice.
  
  
  METHODS
  A hand search of literature on the recommended use of carcinoembryonic antigen (CEA), alphafetoprotein (AFP), prostate specific antigen (PSA), CA-125 and CA-19.9. Systematic reviews and prospective randomised clinical trials of tumour marker applications were also looked at.
  
  
  METHODS
  Five key journals and reference lists of relevant studies were considered.
  
  
  METHODS
  Two authors abstracted relevant data independently. Emphasis was given to guidelines from expert panels. The quality of the guidelines was assessed by availability of level of evidence supporting the recommendations.
  
  
  RESULTS
  Several national and international expert groups have developed guidelines for use of markers for most cancers. CEA, AFP, PSA, CA-125 and CA-19.9 are validated for use in treatment monitoring of colorectal, hepatocellular, prostatic, ovarian and pancreatic carcinomas respectively. AFP and PSA are also useful for cancer screening in high risk groups. CA-125 has limited role in screening while CEA and CA 19.9 are not recommended for cancer screening.
  
  
  CONCLUSIONS
  Not all currently available tumour markers can be used for screening and diagnosis of malignancies. Adherence to recommendations on tumour marker utilisation will improve the cost-effectiveness of these tests.
authors: Department of Human Pathology, College of Health Sciences, University of Nairobi, P.O. Box 19676-00202, Nairobi, Kenya.
authors: A A
authors: AA
authors: Amayo
authors: J G
authors: JG
authors: Kuria