Detection of Ovarian Cancer Cells: Comparison of a Telomerase Assay and Cytologic Examination

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Abstract
Background: Telomerase is an enzyme essential for the normal replication of chromosomes. Telomerase activity is absent in most somatic cells in adults, but it is usually expressed in cancer cells, including ovarian carcinoma cells. Our principal goal was to compare the sensitivity of a telomerase assay, i.e., the telomeric repeat amplification protocol (TRAP) assay, with that of cytologic examination in detecting cancer cells in the peritoneal cavity of patients with ovarian carcinoma. Methods: TRAP assays and cytologic examinations were performed on peritoneal washings and ascitic fluids from 42 patients with active ovarian carcinoma. Control specimens included washings from 29 patients with benign ovarian diseases and ascitic fluids from 14 patients with liver failure. We also evaluated the stability of telomerase in ascitic fluids left unprocessed at room temperature as well as the ability of the TRAP assay to detect cancer cells in mixtures containing large numbers of normal cells. Results: Specimens from 37 (88%) of the 42 patients with ovarian carcinoma tested positive for telomerase. Cytologic examination detected cancer cells in only 27 of the telomerase- positive specimens (i.e., in specimens from 64% of the 42 patients). This difference of 24% (95% confidence interval = 17%–30%) in sensitivity between the two tests was statistically significant (two-sided P = .002). Specimens from five of the patients with ovarian carcinoma were cytologically negative and telomerase negative. All 43 control specimens were cytologically negative, but the TRAP assay detected telomerase in two of them. Telomerase activity was detected in unprocessed samples left at room temperature for 5 days and in mixtures containing a small number of cancer cells and a 2000- to 10 000-fold excess of normal cells. Conclusions: Assaying for telomerase is more sensitive than cytologic examination in detecting cancer cells in the peritoneal cavity of patients with ovarian carcinoma.