Clinical experience using 8 MHz radiofrequency capacitive hyperthermia in combination with radiotherapy: results of a phase I/II study.
OBJECTIVE
Since 1985, the University of Minnesota Hospital and Clinic has investigated the efficacy and safety of 8 MHz radiofrequency (RF) capacitive hyperthermia using the Thermotron RF-8. This study reports the thermometric and clinical results of 119 patients treated with RF hyperthermia in combination with radiotherapy (RT).


METHODS
Of 119 patients, 69 received high-dose RT and 50 patients received low-dose RT because of previous irradiation to the treatment site. The most common anatomic sites treated were within the pelvic cavity or head and neck area. Thirty-three percent and 24% of tumors treated were > 7 cm and > 10 cm in largest diameter, respectively. Forty percent of the patients had deep-seated tumors (depth > 6 cm). Hyperthermia was given as soon as possible after RT twice weekly, allowing at least 72 h between treatments. The objective was to raise intratumoral temperatures to 42-43 degrees C or above for 30-50 min while keeping normal tissue temperatures below 40-41 degrees C.


RESULTS
Of 119 patients, 40% achieved a Tmax tumor temperature of > 42 degrees C and 40% achieved 40-42 degrees C Tmax. Higher Tmax) tumor temperatures were observed as tumor size increased. Tumors > 10 cm in largest diameter had a Tmax of 42.2 degrees C. Tumor depth was not a significant factor for the tumor temperatures achieved. Of 119 patients, 11% achieved complete response and 38% achieved partial response. Of the no-response patients, 34% had symptomatic palliation and 15% had stable disease for at least 12 months after treatment. We were able to treat tumors of patients with subcutaneous fat as thick as 3 cm by precooling the fat for 20 min with 10-15 degrees C saline-filled boluses prior to the initiation of heating. During treatment, 60% of patients complained of varying degrees of pain and 19% had pain that was a factor in limiting treatment. Vital signs were relatively stable and not a factor in limiting treatment.


CONCLUSIONS
The Thermotron RF-8 is a useful hyperthermia device that can raise tumor temperatures to a therapeutic level (i.e., 42 degrees C) in a significant proportion of patients with superficial, subsurface, and deep-seated tumors, with minimal adverse effects, complications, and systemic stress. Further clinical studies using improved thermometry systems are warranted.
Lee
C K
CK
Department of Therapeutic Radiology-Radiation Oncology, University of Minnesota Health Sciences Center, Minneapolis 55455, USA.
Song
C W
CW
Rhee
J G
JG
Foy
J A
JA
Levitt
S H
SH
D000230:Adenocarcinoma / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D003131:Combined Modality Therapy; D005260:Female; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D006358:Hot Temperature; D006801:Humans; D006979:Hyperthermia, Induced / Q000009:adverse effects / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010386:Pelvic Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D012074:Remission Induction; D016019:Survival Analysis