Amplification of the Oncogen HER2 by Immunohistoquemistry and FISH in Patients with Breast Cancer in Colombia. Analysis of 2879 Consecutive Cases Comparing Peripheral Laboratories and a Reference Institution
RE Andrade, A Plata, R Lopez. Hospital Universitario Fundación Santa Fe de Bogota, Bogotá, Colombia
Background: Studies for the detection of the HER2 status are mandatory in every patient with a diagnosis of invasive breast cancer due to its implications as a prognostic and predictive factor for the response to Trastuzumab therapy.
Design: 2879 consecutive cases referred for the determination of the HER2 status by FISH and/or IHQ were retrieved from the data base. The analysis included correlation between the IHQ HER2 score submitted by the peripheral laboratory (PL) and the FISH studies performed in the central laboratory (CL), comparison between de Herceptest Score and the copy numbers by FISH, comparison of the HR results and the HER2 status by IHQ and FISH.
Results: From the total number of cases 2127 HER2 IHQ studies were performed in the (CL), using the Dako Herceptest ; the results are : 67,6 % were negative score 0-1+; 14,6% were indeterminate (2+) ASCO/CAP 2008; 15,6% were 3+ and 2,1 % were not adequate. 1079 cases were studied by FISH (37,5%), 905 shown adequate hybridization signals.83,8%. 631 (69,7%) came from the (PL), and 276 (30,3%) from the (CL). The correlation between the HER2 score performed in the (PL), was 10/41 cases 0-1+ had amplification by FISH corresponding to 24,4,%. 258/529 (2+) 48,7% and 52/61(3+) 85,2% were FISH(+) . In comparison when both studies were performed in the (CL). 1/9 cases HER2 (0+) 11,1% 3/17 HER2(1+) 17,6%,139/241HER2 (2+)57,6% and 9/9 HER2(3+) 100% were FISH positive, from the,only 1/4 cases negative (score 0 and 1) corresponded to an in-house case. (3,8% of false negative).The range of FISH amplification were: 2.65-4.8 for the (0+); 2,2-7,5 for the (1+); 2,2-15.2 for the (2+) and 3,5-14,5 for the (3+). In 280 of the cases studied by FISH the results of the HR. were available, 45,8 of the FISH(+) were RH(+). In 824 of the HER2 cases studied by IHQ the HR were positive in 70,9% of (0+); 84,2 (1+); 71% (2+) and 37,9% o (3+).
Conclusions: Similar to what has being reported in developed countries the false negative and false positive results of the HER2 by IHQ in peripheral laboratories is unacceptable high in Colombia with a false negative rate of 24,4% and a false positive of 14,8%. A very high number of tissue blocks submitted for FISH studies were not adequate, indicating that preanalytical factors have to be improved in Colombia in order to get optimal tissue for molecular studies speciality in the era of the molecular targeting therapies.
Tuesday, March 23, 2010 1:00 PM
Poster Session IV # 14, Tuesday Afternoon