RADIATION PNEUMONITIS IMAGED WITH INDIUM-111-PENTETREOTIDE

Early recognition of radiation pneumonitis enables adequate treatment with a reasonable chance to prevent late sequelae. The feasibility of In-111-pentetreotide in detecting this condition was explored in this study. Methods: The degree of lung uptake of In-111-pentetreotide, eva luated both visually and quantitatively by irradiated-to-nonirradiated area ratios (INIA ratio) from planar images after 24 hr, was analyzed in relation to the radiation field acid compared with ventilation/per fusion (V/Q) images and chest radiographs or CT in 11 patients who had received radiotherapy to the mediastinum or to the internal mammary n odes, 10 of whom were suspected of having clinical radiation pneumonit is. Additional SPECT studies were used to map lung uptake distribution , Results: Indium-111-pentetreotide scans were positive in nine sympto matic patients examined 2-5 mo after radiotherapy; strongly or moderat ely positive in eight patients, one of whom was receiving steroid ther apy without clinical response; and weakly positive in one patient with good steroid response, Indium-111-pentetreotide studies were negative in one asymptomatic patient examined 1 mo after radiotherapy and in o ne symptomatic patient, with subsequent diagnosis of aspecific viral p neumonitis, examined 4 mo after irradiation, Positive In-111-pentetreo tide scans delineated areas of radiation pneumonitis that adequately c orrelated with areas of decreased ventilation/perfusion and x-ray abno rmalities, INIA ratios varied from 1.01 to 2.16 and, in irradiated are as with visible uptake, the lowest value was 1.29, SPECT showed lung u ptake in both superficial and deep lying areas in patients with mantle irradiation fields, whereas distribution was limited to anterior area s in internal mammary lymph node chain irradiation, Conclusion: Indium -111-pentetreotide can detect radiation pneumonitis and may have a rol e in both the differential diagnosis of patients who have complaints a fter radiotherapy, and when supported by quantification in the monitor ing of response to steroid therapy.