[Isotopic indicators in the diagnosis of malignant pleurisies (author's transl)]. / Les indicateurs isotopiques dans le diagnostic des pleurésies malignes.

The tracers that are used in thoracic pathology have an elective tumoural affinity, present such a special reaction towards pleural effusions that we were led to study Bleomycin labelled with Cobalt 57 in 34 cases of pleurisy of various etiologies. The hyperfixation, circumscribed to the effusion in all these cases, presented a double problem : of radiobiological risk and of diagnostic significance. We tried to solve the last problem by means of a precise protocol applied to 16 cases, quantifying comparatively the specific radio-activity of pleural fluid and serum and studying the evolution of the pleural serous gradient, after injection of 2 mCi of labelled Bleomycin in 16 patients with suspected malignant pleurisy. From this limited study, it appeared that the sero-pleural gradient of the tracer, 24 hours after injection, was very high, above 5 and up to 15 in 7 malignant pleurisies out of 8; between 2 and 4 in others. It was sometimes below 5 and less in effusions, non malignant or doubtful. This gradient decreased very rapidly to reach 0 on the fourth day, except in recurring chronic effusions. Pending the confirmation of results, after a prolonged experiment, this protocol appeared valuable for diagnostic and physiopathological reasons.