Changes in hepatic blood flow during regional hyperthermia.

Area of Science:

• Oncology
• Medical Physics
• Hepatology

Background:

• Liver tumors often exhibit altered vasculature.
• Hyperthermia is an emerging cancer treatment modality.
• Understanding blood flow dynamics during hyperthermia is crucial for treatment optimization.

Purpose of the Study:

• To investigate the impact of liver hyperthermia on blood flow in VX2 rabbit liver tumors.
• To differentiate blood flow responses in tumor versus normal hepatic tissue.
• To assess the role of hepatic artery and portal vein in thermal regulation.

Main Methods:

• Utilized a rabbit VX2 liver tumor model.
• Administered 2450 MHz microwave-induced hyperthermia ( > 43°C) to exteriorized livers.
• Measured hepatic arterial and portal venous blood flow using radioactive microspheres before, during, and after hyperthermia.

Main Results:

• Hyperthermia caused a significant decrease in total liver blood flow, predominantly in the hepatic artery supplying the tumor.
• Tumor blood flow was markedly reduced during heating due to exclusive hepatic artery supply, persisting post-treatment.
• Observed temperature differentials of 5-8°C between tumor and normal tissue, linked to reduced tumor blood flow.
• Portal vein had minimal impact on tumor temperature but contributed to normal liver heat dissipation.

Conclusions:

• Hepatic arterial blood flow reduction is the primary mechanism by which hyperthermia depresses tumor perfusion.
• Persistent decreased tumor blood flow suggests vascular collapse, potentially enhancing hyperthermia's anti-tumor effect.
• Differential blood flow significantly influences thermal distribution, creating higher temperatures within tumors.