title: Initial experience using microwave ablation therapy for renal tumor treatment: 18-month follow-up.
abstract: OBJECTIVE
  To assess efficacy and morbidity of microwave ablation (MWA) for small renal tumors in an initial cohort of patients. MWA is a recently introduced thermal needle ablation treatment modality with theoretical advantages compared with radiofrequency ablation, such as greater intratumoral temperatures, lack of a grounding pad, and superior convection profile. However, experience has been limited in the human kidney.
  
  
  METHODS
  Ten patients with a single, solid-enhancing renal tumor from June 2008 to November 2008 received laparoscopic or computed tomography-guided percutaneous MWA at a tertiary referral center with ≥14 months of follow-up. MWA was performed using the Valleylab Evident, 915-MHz MWA system at 45 W with intraoperative biopsy before ablation, and peripheral fiberoptic thermometry to determine the treatment endpoints. The patients were followed up with contrast-enhanced computed tomography at 1 month, 6 months to 1 year, and annually to monitor for tumor recurrence.
  
  
  RESULTS
  The follow-up duration for the 6 male and 4 female patients (mean tumor size 3.65 cm, range 2.0-5.5; mean age 69.8 years) was 17.9 months. The recurrence rate, defined by persistent enhancement, was 38% (3 of 8). The intraoperative and postoperative complication rate was 20% and 40%, respectively.
  
  
  CONCLUSIONS
  MWA resulted in poor oncologic outcomes with a significant complication rate at an intermediate level of follow-up. However, MWA has promising theoretical advantages and should not be discarded. Additional studies should be considered to better understand the microwave-tissue interaction and treatment endpoints for different size renal masses before widespread use.
authors.affiliation: Division of Endourology, Laparoscopy, Minimally Invasive Surgery, Department of Urology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Castle
authors.forename: Nelson
authors.initials: N
authors.lastname: Salas
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Leveillee
mesh_terms: D055011:Ablation Techniques; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy*; D003972:Diathermy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy*; D010535:Laparoscopy; D008297:Male; D008872:Microwaves / Q000627:therapeutic use*; D008875:Middle Aged; D009336:Necrosis; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome