Final Report FUS Grant

The objective of this project was to evaluate the ability of Focused Ultrasound (FUS) induced mild local hyperthermia (40-45°C) to enhance doxorubicin (Dox) delivery in sarcoma tumors of veterinary patients. Hyperthermia is known to reduce interstitial fluid pressure and improve tumor perfusion, thereby elevating intravascular intratumoral drug coverage. Based on this premise, we hypothesized that controlling Dox delivery in real-time within the tumor microenvironment with FUS will improve patient outcomes and thus advance human and veterinary clinical practice. Further, we proposed that compared to Dox alone, low temperature-sensitive liposome (LTSL) that releases its content at close to 40°C will achieve relatively higher drug accumulation in tumors. Although not proposed, we also aimed to assess whether the application of Dox with FUS could invoke systemic antitumor immunity in the treated patients. 5 canine and 1 feline patient with histologically confirmed sarcoma were randomly assigned into two groups (3 patients/group): 1) Dox + FUS, and 2) LTSL+ FUS. In all groups, 0.7mg Dox/kg body weight was administered intravenously over 30min. FUS was initiated immediately after Dox administration and performed for a total of 90min covering <40% of the tumor volume. Results showed that Dox delivery to heated regions significantly exceeded those of the unheated in the sarcoma tumors. Compared to Dox alone cohorts, the drug delivery from LTSL increased by ~4-fold in the heated region and 2-fold in the unheated regions of the treated tumor. Therapeutically, the combinatorial treatment-achieved partial response 2wks post-treatment. Phenotypic characterization of immune cells suggested an increased frequency of T cells in the biopsy and blood samples post-treatment, however, in most cases, they were associated with an enhanced population of pro-tumoral T-reg cells. Overall, Dox delivery in sarcoma tumors is enhanced with FUS heating, and these correlate with improved local and systemic antitumor immunity, and tumor regressions.