Response of blood flow to hyperthermia in human prostate tumors: Opportunities for enhanced radiation effect and drug delivery.
ABSTRACT
Background: Tissue perfusion may be a significant factor affecting outcome of prostate cancer treatment. Hyperthermia has been shown to have beneficial anti-cancer effects when combined with other anti-neoplastic modalities including radiation, chemotherapy, and immunotherapy. For instance, hyperthermia may increase prostate perfusion resulting in radiosensitization through increased oxygenation and chemotherapy through enhanced drug delivery. We previously reported significant benefit to the addition of hyperthermia to radiation on a phase II trial for men with locally advanced prostate cancer. To better understand tissue perfusion in patients with prostate cancer and response to hyperthermia, we measured perfusion levels in patients on this trial before and after hyperthermia.
Methods: Prostate perfusion was measured before and immediately after heating in a total of 21 hyperthermia treatments in 14 patients with prostate cancer. A trans-rectal ultrasound device with a water cooled jacket was used to heat the prostate. Prostate tissue temperatures were measured using three multisensory thermocouple probes. Perfusion was measured with the TDP-200 Thermal Diffusion Probe, a thermistor-based device which quantifies perfusion with a modified wash-out technique.
Results: In 19 treatments in which perfusion was measured before heating, average and standard deviation was 18.3 ± 10.6 ml/100g-min and in 17 treatments in which perfusion was measured after heating, it was 30.7 ± 20.8 ml/100g-min. This represents a statistically significant increase of 68% (p = 0.018). Perfusion increased 12 of 15 treatments in which measurements were obtained before and after hyperthermia. Notably, prostate tissue that was most ischemic prior to heating experienced the largest heat-induced perfusion increase.
Conclusions: Prostate perfusion increased significantly with a majority of hyperthermia treatments. Enhanced prostate oxygenation may have been a contributing factor to the benefit noted with hyperthermia in this phase II trial. The use of hyperthermia to augment prostate perfusion to enhance radiation, chemotherapy, and immunotherapy warrants further investigation.