Reduced beta adrenoceptor density in vivo in human lung tumours: a preliminary study with positron emission tomography.

BACKGROUND: Reduced beta adrenergic receptor density in tumours has been reported in previous in vitro studies. The aim of the present study was to assess whether this occurs in vivo. METHODS: Pulmonary beta adrenoceptors were imaged and quantified in vivo using positron emission tomography (PET) and the beta antagonist radioligand (S)-[11C]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 cases, adenocarcinoma in one, carcinoid tumour in one, and large cell carcinoma in one. The regional blood volume and extravascular tissue density were also measured using PET. Regions of interest were drawn for both non-tumour and tumour lung tissue. RESULTS: The mean (SD) blood volume 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 0.653 (0.133) g/ml in tumour regions, substantially higher 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 than the value of 9.9 (1.6) pmol/g found in adjacent normal lung--a difference of 48%. CONCLUSIONS: In vivo beta adrenoceptor density is reduced in human lung tumours.