Abstract 3278: The effect of cold ischemia time on protein expression in breast cancer tissues

Abstract

Abstract Background: HER2 testing is a critical tool for determining the molecular subtypes of breast tumors. However there are various factors which may influence the accuracy of HER2 immunohistochemistry (IHC) results. Those factors have been addressed by the American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) and outlined in the updated 2013 guideline. The ASCO/CAP guidelines advise limiting the tissues cold ischemia time as much as possible specifically to no more than one hour. A tissue's cold ischemia time is defined as the time from the tissues removal from the patient to the initiation of fixation. Our institution works with several collaborators for whom postoperative tissue banking is performed for the majority of breast resection specimens. In most cases, the procedure of tissue excision takes 30-60 minutes. However, in some cases cold ischemia time is increased more than 60 minutes. Presently, there is limited information available on the effect of cold ischemia on HER2 IHC staining. In this study, we compared HER2 IHC results for breast tumor specimens to determine the effect of prolonged cold ischemia time on protein expression. HER2 status was confirmed by the in-situ hybridization method (FISH). Design: In this study we evaluated HER2 status using two different FDA-approved FISH and an FDA-approved IHC assay in a large cohort of invasive breast carcinomas with differing cold ischemia time in pathology laboratories at the University of Chicago (U of C) and in Ibadan, Nigeria (IMRAT). Cold ischemia time was used to stratify the samples into two groups 1-3 h (n=27 U of C cases) and >3h (n=79 MRAT cases). Both FISH and IHC were evaluated using ASCO/CAP scoring criteria. Tissue microarrays (TMAs) including duplicate 1.0-mm cores of invasive breast carcinoma were constructed utilizing formalin-fixed, paraffin-embedded tissue of 106 breast cancer patients, who had surgery at the U of C and IMRAT. HER2 status determination was performed on the TMAs utilizing IHC with the HercepTest (DAKO, USA), and FDA-approved FISH assay (PathVysions, Abbott Molecular, USA). Results: Only 3.7% of the cases examined in the 1-3 h cold ischemia time group had a discrepancy in the HER2 IHC and FISH result. However, within the >3 h cold ischemia time cohort a total of 7.6 % were identified with a minor discrepancy between the HER2 IHC and FISH results. Conclusions: In this study, we compared the effect of cold ischemia time on standard HER2 testing methodologies including FISH and IHC. Comparison of FISH and IHC showed that IHC did not identify several FISH HER2-amplified cases at >3h cold ischemia times. These findings are important in consideration of specimen preparation and could have an effect on specimen handling and fixation guidelines. Citation Format: Galina F. Khramtsova, Andrey I. Khramtsov, Lise Sveen, Abayomi Odetunde, Oyinlolu Olorunsogo Adeyanju, Olufunmilayo I. Olopade, Oluwasola A. Olayiwola. The effect of cold ischemia time on protein expression in breast cancer tissues. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3278. doi:10.1158/1538-7445.AM2014-3278