Focused microwave phased array thermotherapy for ablation of early-stage breast cancer: results of thermal dose escalation.
BACKGROUND
Tumor ablation as a means of treating breast cancer is being investigated. Microwave energy is promising because it can preferentially heat high-water-content breast carcinomas, compared to adipose and glandular tissues.


METHODS
This is a prospective, multicenter, nonrandomized dose-escalation study of microwave treatment. Thermal dose was measured as (1) thermal equivalent minutes (cumulative equivalent minutes; CEM) of treatment relative to a temperature of 43 degrees C and (2) peak tumor temperature. Microwaves were guided by an antenna-temperature sensor placed percutaneously into the tumor. Outcomes measured were pathologic response (tumor necrosis) side effects.


RESULTS
Twenty-five patients (mean age, 57 years) were enrolled. The mean tumor diameter was 1.8 cm. Tumoricidal temperatures (>43 degrees C) were reached in 23 patients (92%). Tumor size was unchanged after thermotherapy (P = not significant). Pathologic necrosis was achieved in 17 (68%) patients. Complete necrosis of the invasive component was achieved in two patients. One hundred forty CEM is predictive of a 50% tumor response, and 210 CEM is predictive of a 100% tumor response (P =.003). Univariate linear regression predicts that peak tumor temperatures of 47.4 degrees C and 49.7 degrees C cause a 50% tumor response and a 100% tumor response, respectively.


CONCLUSIONS
Thermotherapy causes tumor necrosis and can be performed safely with minimal morbidity. The degree of tumor necrosis is a function of the thermal dose. Future studies will evaluate the impact of high doses of thermotherapy on margin status and complete tumor ablation.
Vargas
Hernan I
HI
Harbor-UCLA Medical Center, Torrance, California, USA. hvargas@ucla.edu
Dooley
William C
WC
Gardner
Robert A
RA
Gonzalez
Katherine D
KD
Venegas
Rose
R
Heywang-Kobrunner
Sylvia H
SH
Fenn
Alan J
AJ
D001943:Breast Neoplasms / Q000628:therapy*; D005260:Female; D006801:Humans; D006979:Hyperthermia, Induced / Q000009:adverse effects / Q000379:methods*; D016014:Linear Models; D008872:Microwaves / Q000627:therapeutic use*; D008875:Middle Aged; D015999:Multivariate Analysis; D009336:Necrosis; D011446:Prospective Studies