gms | German Medical Science

Objective: In comparison with MRT, amino acid PET using O-(2-[F-18]fluoroethyl)-L-tyrosine (FET) allows a better demarcation of tumour tissue from unspecific tissue reactions. In experimental and clinical studies, an unspecific uptake of FET could be observed in non-neoplastic brain lesions and in areas of reactive astrogliosis. Surgical interventions might induce tissue responses accompanied by reactive astrogliosis that potentially could lead to an unspecific accumulation of FET. The aim of this study was to examine the cerebral FET uptake after tumour resection in a rat glioma model.

Method: In 21 male Fischer rats, F98 gliomas were implanted into the cerebral cortex and resected after one week of tumour growth. At different time points after surgery (2, 3, 7, 14 days; n=5-6), the rats were injected intravenously with FET. One hour after injection of FET, animals were sacrificed and coronal cryosections of the brains were produced and evaluated by autoradiography and histological stainings. Tracer uptake was determined by regions of interest and quantified by lesion to brain (L/B) or tumour to brain (T/B) ratios.

Results: In the early phase (2-3 days) after tumour resection, all animals demonstrated a slightly increased unspecific uptake of FET in the vicinity of the surgical defect (L/B: 1.79-1.94 ± 0.17-0.26) which decreased significantly after 7-14 days (L/B: 1.57-1.39 ± 0.23-0.18; p<0.05). At each time point, the tumour tissue exhibited a considerably higher FET uptake (4.4 ± 0.8; p<0.05) and could be separated from unspecific FET uptake in the tissue.

Conclusions: Surgical resection of the tumour causes a slightly increased uptake of FET in the vicinity of the resection area in the early phase after tumour resection which decreases 7-14 days after intervention. At each time point, unspecific FET uptake in that area could be clearly separated from tumour tissue. Thus, the correct identification of residual tumour tissue after surgery for planning of radiotherapy appears to be unaffected by unspecific FET uptake.