[Fluorine-18]Fluorodeoxyglucose Positron Emission Tomography, DNA Ploidy and Growth Fraction in Squamous-Cell Carcinomas of the Head and Neck

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Abstract
Background: Positron emission tomography (PET) offers an opportunity to examine noninvasively cellular functions with different tracers. [18F]Fluorodeoxyglucose (FDG) is most commonly used in identifying malignant tumors. Several tumor biologic characteristics (tumor cell viability, growth faction, treatment response to radiation, cell membrane dysfunction, recurrence rate) are suggested to be characterized by [18F]FDG PET. The aim of this study was to assess which other tumor biologic characteristics of squamous-cell carcinoma of the head and neck are correlated with [18F]FDG PET. Methods: [18F]FDG PET was performed in 14 patients with squamous-cell carcinomas of the upper digestive tract (TNM classification T2–T4, N1–N3). After attenuation correction, predefined areas of the tumor were semiquantitatively analyzed by the technique of the region of interest and calculated as standard uptake values (SUV). Afterwards, 5 biopsies of different tumor regions were obtained during endoscopy in each patient under general anesthesia, and a correlation between SUV of [18F]FDG PET and tumor biologic parameters was attempted. These parameters included: quantitative DNA measurements (i.e. 2c deviation index, 5c exceeding rate), immunohistochemical assessment of growth fraction (i.e. Ki67-MIB-1, PCNA) along with morphological tumor front grading. Results: The results revealed a marked variation of proliferation and cellular differentiation in various regions of the tumor for all parameters examined. There was a close correlation between [18F]FDG uptake and growth fraction (r = 0.83 for Ki67-MIB-1 and r = 0.8 for PCNA). A poor correlation was found between DNA aneuploidy (r = 0.4) or tumor front grading (r = 0.12) and [18F]FDG uptake. Conclusions: Our results confirm previous clinical and histologic observations that squamous-cell carcinomas of the upper digestive tract are heterogeneous tumors. Ki67 antigen, which has been shown to be of predictive value for proliferation and individual prognosis, correlated with [18F]FDG uptake. Using [18F]FDG PET, the main proliferation centers of inhomogeneous squamous-cell carcinomas could be identified with possible clinical implications for patient management.