title: Focused microwave phased array thermotherapy for ablation of early-stage breast cancer: results of thermal dose escalation.
abstract: 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.
authors.affiliation: Harbor-UCLA Medical Center, Torrance, California, USA. hvargas@ucla.edu
authors.forename: Hernan I
authors.initials: HI
authors.lastname: Vargas
authors.forename: William C
authors.initials: WC
authors.lastname: Dooley
authors.forename: Robert A
authors.initials: RA
authors.lastname: Gardner
authors.forename: Katherine D
authors.initials: KD
authors.lastname: Gonzalez
authors.forename: Rose
authors.initials: R
authors.lastname: Venegas
authors.forename: Sylvia H
authors.initials: SH
authors.lastname: Heywang-Kobrunner
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Fenn
mesh_terms: 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