Tumor markers accuracy

Abstract

Considering the increasing number ofthe so callediumox markers and its systematic use in the medicai practice, an assessment was made through Medline© 1995 at the Central Library of the Brazilian National Cancer Institute - INCA, and 95 abstracts, published from 1995 to April 1997 were reviewed. It was noted that tumor validity is higher for some types of tumor and for some prognostic factors; that few of them are of real clinical utility, either for prevention, diagnosis or prognosis, as most of them are only significant when there is some signs or symptoms of the disease; that most of the studies are somewhat repeated, as same markers are assessed in different tumors; and there are studies which refer tofew cases, or very few, and because of this the results are inconsistent. In this article, tumor markers are classified by types (genes, genetic expressions, circulating substances, intracellular substances, cellular membrane receptors and cell proliferation indices) and according to their purposes (risk assessment, screening, differential diagnosis, staging, assessment of therapeutic efficacy, post treatment follow-up, and prognosis) and are correlated with the tumor(s) in which they were analyzed. It is presented three groups of validation criteria (statistic, biomedical and uses) and it is summarized, from 16 other bibliographic references, the clinicai utility of breast cancer markers [DNA, Phase S, DNA index, C-erbB-2 (HER-2/neu), p53 e CAT-D, CAI 5.3 and CEA - non-valid; hormonal receptors for indication ofadjuvant orpalliative hormoniotherapy - valid]; colo-rectal cancer markers (LASA, CA 19.9, DNA index, phase S, P53 and ras - non-valid; CEA for staging and surgical planning, and for postoperative follow up - a dosage series every 2-3 months for two years, if one suspects of liver metastasis in surgical stages II and III - valid) and of prostate cancer (PSA useful for detection, but associated with rectum hand examination in males over 40-50 years ofage, as indicatives of the need of more accurate studies, and for posttreatmentf ollow up). It is out of the question the utility of alpha-fetoprotein (aFP) and human chorionic gonadotropin (HCG), for staging, assessment of the therapeutic response and posttreatment follow up of cancer of testis (aEP and HCG) and of gestational trophoblastic disease (HCG). There is also no doubt that identifying cell differentiation markers are valid for pathological diagnosis of leukemias and lymphomas. From this study, five dilemmas are identified: 1) absence of signs and symptoms versus a positive tumor marker; 2) detection ofasymptomatic relapsevexsus quality and length ofsurvival; 3) non-malignant cause versus marker increase; 4) false-positive result versus treatment; and 5) low risk of tumor progression versus treatment. It is concluded that, except for utility established for diagnosis, posttreatment follow-up or prognosis for some types of cancer, the physician must know not only tumor markers and their abbreviations, but also their accuracy and to have an opinion, criteria and method in their clinical use.