Ovarian cancer is the leading cause of death among women with gynecologic malignancies.1 In dogs, the prevalence of ovarian cancer is low and ranges from 0.5% to 6.2%; however, the true rate of ovarian cancer in dogs is likely underestimated because many female dogs undergo elective ovariohysterectomy or oophorectomy at a young age for the purpose of sterilization.2 Ovarian tumors in dogs are histologically similar to those in women; therefore, dogs may serve as a useful species for investigating ovarian neoplasia in women.3 Typically, in both dogs and women, ovarian cancer is highly malignant and metastatic and often remains undetected until the patient is at an advanced stage of the disease.
In women, complete cytoreductive surgery to eliminate all gross residual disease is the treatment of choice for advanced ovarian cancer and has been shown to dramatically improve the likelihood of survival.4–6 Cytoreductive surgery consists of extirpation of the primary ovarian tumor as well as any metastatic tumors. Although minimally invasive cytoreductive surgical techniques have been described,7 cytoreduction of ovarian tumors is typically accomplished by sharp dissection and conventional electrocautery, which may lead to hemorrhage and associated complications in women. In veterinary medicine, laparoscopic techniques for oophorectomy and ovariohysterectomy in dogs have also been well described, and those minimally invasive methods are associated with lower morbidity rates and faster recovery times, compared with traditional open surgical methods.8–10 However, complications can develop following minimally invasive oophorectomy and ovariohysterectomy procedures,11,12 and efforts to develop less invasive alternatives for surgical sterilization of female dogs continue.13–15
In women with stage II/III hormone receptor-positive breast cancer, ovarian ablation with goserelin significantly improves survival times.16 Hyperthermic ablation technology, such as MWA, has evolved rapidly over the past 30 years and is commonly used in human oncology for minimally invasive percutaneous treatment of primary and metastatic tumors.17 Ablation is considered a first-line treatment and is preferred over surgical resection for small hepatocellular carcinomas in human patients with preserved liver function who are not transplant candidates.18 In dogs, MWA has been used for the treatment of hepatic neoplasia19,20 and ablation of pulmonary metastases via thoracoscopy.21 Benefits of percutaneous hyperthermic ablation therapy relative to surgical resection include decreases in morbidity, hemorrhage, duration of hospitalization, and cost.22–26 Compared with radiofrequency ablation, MWA has several advantages including a smaller probe diameter, faster ablation times, more versatile energy deposition, reduced heat-sink effects, and the ability to perform multiple synchronous ablations.27–31
Results of PubMed searches conducted on August 1, 2017, and July 1, 2018, with the search parameters “microwave ablation” and “ovarian” or “ovaries” suggested that MWA of ovarian tissue has not been described in dogs or human patients. In addition to the treatment of ovarian neoplasia, potential applications of MWA in regard to ovarian tissue include elective sterilization and treatment of hyperplastic (cystic) conditions in both veterinary and human patients. The objectives of the study reported here were to determine the optimal MWA energy profile (ie, duration of ablation required at an emission power of 45 W) necessary for complete destruction of clinically normal canine ovarian tissue as determined by histologic assessment of cell viability and to evaluate the efficacy and feasibility of the use of percutaneous ultrasonography and laparoscopy to guide MWA of ovarian tissue in dogs.
All described procedures were performed at the University of Florida College of Veterinary Medicine.
This manuscript represents a portion of a thesis submitted by Dr. Verpaalen to the Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida as partial fulfillment of the requirements for a Master of Science degree.
Supported by a Consolidated Faculty Research Development Award Grant from the University of Florida College of Veterinary Medicine. NeuWave Medical, Madison, Wis, provided the microwave probes used in the study. The funding sources had no involvement in the study design, data analysis and interpretation, or writing and publication of the results for this project.
The authors declare that there were no conflicts of interest.
Presented as a poster presentation at the American College of Veterinary Surgery Summit, Phoenix, October 2018.
The authors thank Cat Monger and Melissa Brown for technical assistance.
Interquartile (25th to 75th percentile) range
Nicotinamide adenine dinucleotide diaphorase
Certus PR15 Ablation Probe, NeuWave Medical, Madison, Wis.
Bio-zyme, Osceola Supply, Tallahassee, Fla.
Ligasure, Covidien, Saint-Laurent, QC, Canada.
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