REDUCED BETA-ADRENOCEPTOR DENSITY IN-VIVO IN HUMAN LUNG-TUMORS - A PRELIMINARY-STUDY WITH POSITRON EMISSION TOMOGRAPHY

Background - Reduced beta adrenergic receptor density in tumours has b een reported in previous in vitro studies. The aim of the present stud y was to assess whether this occurs in vivo. Methods - Pulmonary beta adrenoceptors were imaged and quantified in vivo using positron emissi on tomography (PET) and the beta antagonist radioligand (S)-[C-11]CGP- 12177 in five men with lung tumours of mean age 58 years (range 42-68) . The histology of the tumours was squamous cell carcinoma in two case s, adenocarcinoma in one, carcinoid tumour in one, and large cell carc inoma in one. The regional blood volume and extravascular tissue densi ty were also measured using PET. Regions of interest were drawn for bo th non-tumour and tumour lung tissue. Results - The mean (SD) blood vo lume was 0.142 (0.025) ml/ml in tumour regions and 0.108 (0.010) ml/ml in normal lung regions - a difference of 31%. Mean (SD) extravascular tissue density was (0.133) g/ml in tumour regions, substantially high er than in normal lung regions (0.157 (0.021) g/ml). On the contrary, beta receptor density was 5.1 (1.8) pmol/g in tumour regions, lower th an the value of 9.9 (1.6) pmol/g found in adjacent normal lung - a dif ference of 48%. Conclusions - In vivo beta adrenoceptor density is red uced in human lung tumours.