RADIATION PNEUMONITIS AFTER SELECTIVE INTERNAL RADIATION TREATMENT WITH INTRAARTERIAL (90)YTTRIUM-MICROSPHERES FOR INOPERABLE HEPATIC-TUMORS

Purpose: To investigate the clinical, histopathological, and radiologi cal features of radiation pneumonitis arising as a complication of sel ective internal radiation treatment for liver tumors. To correlate the development of radiation pneumonitis with the degree of lung shunting as assessed by (99m)Technetium-labeled macroaggregated albumin (Tc-MA A) scan. Methods and Materials: Five out of 80 patients who had inoper able hepatic tumors and underwent treatment with intraarterial(90)Yttr ium- (Y-90)-microspheres, developed progressive restrictive ventilator y dysfunction without an infective or cardiovascular cause. Histopatho logical evidence of a pneumonitis and the presence of microspheres in the lung tissue suggested a diagnosis of radiation pneumonitis. The cl inical course, radiological and histopathological findings, percentage tumor shunting to the lungs (lung shunting, as predicted by gamma cam era scanning after intraarterial Tc-MAA), and the estimated radiation dose to the lungs were analyzed. In an attempt to reduce pulmonary shu nting of the microspheres, three patients received partial hepatic emb olization with inert particles before selective internal radiation the rapy. Results: In the five patients who developed radiation pneumoniti s, lung shunting percentages (as predicted by Tc-MAA scan) ranged from 13.1 to 45.6% (median 23.7%). The estimated whole lung radiation dose ranged from 10.43 Gy to 36.44 Gy (median 25.04 Gy). Among 75 patients who did not develop radiation pneumonitis, the percentage lung shunti ng ranged from less than 1% to 15% (median 6%). Nine patients had lung shunting greater than 13% and five of them developed radiation pneumo nitis, whereas this developed in none of those in whom shunting was be low 13%. The onset of radiation pneumonitis ranged from 1 to 6 months after internal radiation treatment. All five patients exhibited charac teristic plain radiographic and computerized tomographic changes compr ising extensive consolidation with well-defined lateral margins. Clini cal improvement after corticosteroid treatment was seen in two patient s. Three patients died from respiratory failure and two from other cau ses. Partial hepatic arterial embolization reduced the degree of lung shunting to less than 13%, but did not prevent the development of radi ation pneumonitis. Conclusion: Radiation pneumonitis may become a comp lication after intraarterial Y-90-microspheres treatment when lung shu nting, as assessed by Tc-MAA scan, is high (above 13%). Prescribed act ivity of Y-90 and lung shunting of Tc-MAA should be considered togethe r before giving selective internal radiation (SIR) therapy for hepatic tumors, and preferably avoided if the lung shunting is above 13%.