ABSTRACT
Although tissue microarrays (TMA) have been widely used for a number of years, it is still not clear how many core biopsies should be taken to determine a reliable value for percentage positivity or how much heterogeneity in marker expression influences this number. The first aim of this study was to validate the human visual semi-quantitative scoring system for positive staining of tumour tissue with the exact values determined from computer-generated images. The second aim was to determine the minimum number of core biopsies needed to estimate percentage positivity reliably when the immunohistochemical staining pattern is heterogeneous and scored in a non-binary way. Tissue sections from ten colorectal cancer specimens were stained for carbonic anhydrase IX (CA IX). The staining patterns were digitized and 400 artificial computer-generated images were generated to test the accuracy of the human scoring system. To determine the minimal number of core biopsies needed to account for tumour heterogeneity, 50 (artificial) core biopsies per section were taken from the tumoural region of the ten digitally recorded full tissue sections. Based on the semi-quantitative scores from the 50 core biopsies per section, 2500 x n (n = 1-10 core biopsies) experimental core biopsies were then generated and scores recorded. After comparison with field-by-field analysis from the tumoural region of the whole tissue section, the number of core biopsies that need to be taken to minimize the influence of heterogeneity could be determined. In conclusion, visual scoring accurately estimated the percentage positivity and the percentage tumour present in a section, as judged by comparison with the artificial images. The exact number of core biopsies that has to be examined to determine tumour marker positivity using TMAs is affected by the degree of heterogeneity in the expression pattern of the protein, but for most purposes at least four is recommended.
Subject(s)
Adenocarcinoma/metabolism , Biomarkers, Tumor/metabolism , Colorectal Neoplasms/metabolism , Neoplasm Proteins/metabolism , Tissue Array Analysis/standards , Adenocarcinoma/pathology , Biopsy , Carbonic Anhydrase IV/metabolism , Colorectal Neoplasms/pathology , Humans , Image Processing, Computer-Assisted/methods , Immunoenzyme Techniques , Reproducibility of Results , Tissue Array Analysis/methodsABSTRACT
AIM: To determine the differences in downstaging, local control (LC), disease free survival (DFS) and overall survival (OS) between combined pre-operative chemoradiation and pre-operative radiotherapy alone in the treatment of resectable rectal cancer. METHODS: One hundred and ten patients who underwent pre-operative radiotherapy or chemo-radiotherapy were reviewed. Fifty-seven patients were treated with radiotherapy (30 Gy/3 Gy) alone and 53 patients with chemo-radiotherapy (bolus 5FU+45 Gy/1.8 Gy). The median interval between the end of neo-adjuvant treatment and surgery was 28 and 46 days for the patients treated with radiotherapy alone and chemo-radiotherapy. RESULTS: The groups were homogeneously distributed for all characteristics except for cN-stage with more clinically node positive patients in the combined modality treatment group (47 vs 73%). A significant downstaging for tumour and/or lymph node status was observed in both groups. More ypT0-x-is were observed after chemoradiation than after radiotherapy alone (26 vs 7%; p=0.02). The local control rate at 3 years was 94% for both groups. DFS after radiation and chemoradiation was comparable with a 3-year DFS of 83 and 88%, respectively. CONCLUSION: Both pre-operative schemes have similar outcomes concerning DFS, OS and LC. Tumour downstaging is associated with improved survival.