Adenoma-carcinoma sequence in colorectal tumors demonstrated by glucose transporter type 1 expression and FDG-PET

Abstract

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Objectives: Adenomatous polyp in large bowel progresses to carcinoma. FDG uptake of colon polyp mediated by glucose transporter type 1 (Glut-1) expression may be affected by progression of the adenoma-carcinoma sequence. Thus, we investigated Glut-1 expressions of the adenomatous polyps and carcinomas, and correlated them with FDG-PET findings.

Methods: Thirty nine patients (male:female = 29:10, age = 58±11 years), who underwent colonoscopy and FDG-PET within 1 month interval, were enrolled. There were 26 tubular adenomas (TA), 4 tubulovillous or villous adenomas (VA), and 11 adenocarcinomas (CA). Non-tumorous hyperplastic or inflammatory polyps were excluded. Colonoscopic biopsy samples were immunostained using polyclonal anti-Glut-1 antibody (Neomarkers). Glut-1 expressions were evaluated for percentages of Glut-1 positive proportion, staining intensity (grade 0-3), and expression pattern (membranous or cytoplasmic). FDG uptake on FDG-PET was dichotomized as presence or absence.

Results: The percentage of Glut-1 positive proportions were not different among TA (46.5±31.5%), VA (57.5±44.3%), and CA (49.1±38.3%) (p>0.05). However, Glut-1 staining intensities were significantly greater in VA (2.8±0.5) and CA (2.5±0.7), than TA (1.7±0.6) (p<0.005). Glut-1 staining patterns were predominantly membranous type in CA (54.5%=6/11), but VA (25.0%=1/4) and TA (3.9%=1/26) were mostly cytoplasmic (p<0.005). All CAs were PET (+), but all TAs were PET (-). One VA was PET (+), 2 VAs PET (-), and one VA unevaluable.

Conclusions: Adenoma-carcinoma sequence in colorectal tumors was clearly demonstrated by Glut-1 expression and FDG-PET. These findings suggest potential application of FDG-PET to early detection of pre-cancerous adenomas.