Re: Gold Nanoshell-Localized Photothermal Ablation of Prostate Tumors in a Clinical Pilot Device Study.

available at http://www.ncbi.nlm.nih.gov/pubmed/31451630 Editorial Comment: As the interest in focal therapy for prostate cancer grows, a number of unique approaches to deliver therapy locally to regions of the prostate have emerged. In this report the authors describe a novel, elegant approach in which they combine principles of physics, biomaterials and ablative thermal energy. The treatment strategy is predicated on the observation that tiny hollow particles of gold (nanoshells) are capable of altering the wavelength of laser light, thereby creating heat selectively in regions where the particles are dispersed. The nanoshells accumulate preferentially in regions of tumor due to leaky vasculature and, as such, when laser light is delivered to the region of the tumor, the nanoshells allow the dual effect of magnifying the thermal ablation to the region of the tumor while minimizing thermal energy to the surrounding area. In this study the authors used systemic gold nanoshell delivery, followed by tumor localization through magnetic resonance imaging-ultrasound fusion for placement of laser fibers and delivery of near infrared laser energy. Despite the novelty of the approach, the study generates a number of questions. The authors report successful ablation of 16 tumors in 15 men among 16 in whom the procedure was attempted. A targeted biopsy showed residual cancer in 4 of 16 treatment zones at 3-month followup, and in 2 of 16 at 12-month followup. An additional 2 men had clinically significant cancer on systematic biopsy at 12 months. The authors attribute the cases with positive biopsy at 3 months and negative biopsy at 12 months to an abscopal effect in which inflammatory response may destroy the residual tumor, although one has to question whether this is simply a sampling effect. Among men with positive biopsies in the treated zone at 12 months the biopsies were negative at 3 months. This finding perhaps illustrates that in the setting of focal ablative therapy the oncologic efficacy of the intervention is heavily dependent on the rigor of the resampling following intervention. While the true oncologic efficacy of this treatment method is difficult to determine without further followup, this approach is certainly unique and focuses on the critical balance of tumor destruction and preservation of surrounding structures. Nonetheless, the adequacy of margin remains a critical consideration, given the previously noted high rates of margin failure in laser ablated cases, and will rely on complete and consistent dispersion of nanoshells throughout the tumor. Samir S. Taneja, MD Suggested Reading Stern JM, Stanfield J, Kabbani W et al: Selective prostate cancer thermal ablation with laser activated gold nanoshells. J Urol 2008; 179: 748. Natarajan S, Jones TA, Priester AM et al: Focal laser ablation of prostate cancer: feasibility of magnetic resonance imaging-ultrasound fusion for guidance. J Urol 2017; 198: 839. Eggener SE, Yousuf A, Watson S et al: Phase II evaluation of magnetic resonance imaging guided focal laser ablation of prostate cancer. J Urol 2016; 196: 1670. Taneja SS, Bennett J, Coleman J et al: Final results of a phase I/II multicenter trial of WST11 vascular targeted photodynamic therapy for hemi-ablation of the prostate in men with unilateral low risk prostate cancer performed in the United States. J Urol 2016; 196: 1096. PROSTATE CANCER 31 Copyright © 2019 American Urological Association Education and Research, Inc. Unauthorized reproduction of this article is prohibited.