Hyperthermia increases accumulation of technetium-99m-labeled liposomes infeline sarcomas

The effect of hyperthermia on the accumulation of technetium-99m-labeled li posomes was studied in feline sarcomas, Each cat received two separate inje ctions of liposomes, The first was used to quantify the amount of technetiu m-99m-labeled liposomes within the tumor under normothermic conditions. The second injection was made at the beginning of a 60-min hyperthermia proced ure, Planar scintigraphy was used to measure the activity of technetium-99m -labeled liposomes within the tumor at predetermined times up to 18 h after injection. Regions of interest were drawn for the tumor, lungs, liver, kid ney, and aorta. Counts in the regions of interest were decay corrected. Cou nts/pixel in the tumor under normothermic and hyperthermic conditions were normalized to aorta counts/pixel, A total of 16 cats were eligible for the study. In two of the 16 cats, incomplete count data precluded analysis, In the remaining 14 cats, hyperthermia resulted in a significant increase in l iposome accumulation in the tumor (P = 0.001), Tumor volume ranged from 1.2 to 236.2 cm(3), and thermal dose ranged from 2.0 to 243.3 CEM43CT90 (equiv alent time that the 10th percentile temperature was equal to 43 degrees C), There was not a relationship between either tumor volume or hyperthermia d ose on the magnitude of increased liposome accumulation, suggesting that th is method has application across a range of tumor volumes and degrees of he atibility.