A phase I and II clinical trial of a newly developed ultrasound hyperthermia system with an improved planar transducer.

ABSTRACT

PURPOSE: The clinical usefulness of a newly developed ultrasound hyperthermia system was evaluated. METHODS AND MATERIALS The hyperthermia system uses a modified planer transducer operated at frequencies of 0.5, 1.0, and 1.5 MHz. The transducer has a nonvibrating part at the center to reduce the central hot spot. Frequency sweeping technique is also used to eliminate the annular hot spot around the center. Thirty-eight tumors in 29 patients were examined in this study. In 35 tumors, hyperthermia was given in conjunction with irradiation and/or chemotherapy, and in the remaining 3 tumors, hyperthermia alone was given. In all, a total of 153 hyperthermia sessions were performed. RESULTS: The number of hyperthermia sessions per tumor ranged from 1 to 7 (mean, 4.0 +/- 1.3). The number of intratumor thermometry points per session ranged from 1 to 8 (mean, 4.3 +/- 1.5). The average intratumor temperature for tumors with a maximum depth of <3 cm, 3-6 cm, and >6 cm was 42.1 +/- 1.2, 41.7 +/- 1.4, and 39.9 +/- 2.0 degrees C, respectively. The percentage of monitored intratumor points with temperature exceeding 42 degrees C was 56 +/- 31%, 43 +/- 34%, and 21 +/- 24%, respectively. Of the 30 evaluable tumors treated with combined irradiation, 12 showed complete response, 14 partial response, and 4 no change. Observed complications included pain at the treatment site in 13 of the 153 treatment sessions and vesicle formation in 3 of the 38 treatment sites. No serious complication was seen. CONCLUSIONS: These results indicate that the newly developed ultrasound hyperthermia system is clinically useful for the treatment of localized superficial and subsurface tumors with a maximum tumor depth of no more than 6 cm.