Ask the Experts – Ardeshir R. Rastinehad, DO

Question 1. How did you come up with the idea to use gold nanoparticles for the photothermal ablation of prostate tumors?

Answer
Nanospectra Biosciences reached out to Dr Steven Canfield, of the University of Texas Health Science Center at Houston, as a possible collaborator. Dr Canfield and I were at a conference together having dinner and he mentioned that there may be a trial that I could help with since he did not know of any technology that was available at the time to perform the treatments. I was excited to say that I had just started developing the first generation transperineal MRI-US fusion biopsy device with Philips Healthcare and it would work perfectly. From there the rest is history. The treatment (AuroLase Therapy) is being developed by Nanospectra Biosciences and is based on technology invented by Dr Naomi Halas, of Rice University, and Dr Jennifer West, of Duke University.

Question 2. What is the scientific basis for the treatment?

Answer
The gold nanoparticles are biocompatible gold-silica nanoshells with a diameter of 150 nm. They are 50 times smaller than a red blood cell. They were designed to absorb light at near-infrared wavelengths of high tissue transparency. That is, the light passes easily through tissue. When infused into a patient, the particles circulate in the bloodsteam and are deposited in the prostate tumors. Most solid tumors have leaky vasculatures, so particles build up in the tumors. Laser light in the near-infrared spectrum is delivered to the tumor, where the particles absorb the energy and heat up and cause ablation. Our premise was that we could create a focal ablation that is tumor specific and thus decrease possible side effects such as erectile dysfunction and urine leakage that occur with non-targeted ablation therapies. The treatment could be applied to other solid organ malignancies besides prostate cancer.

Question 3. How is the procedure performed?

Answer
Patients undergo a standard biopsy and an MRI-ultrasound (US) fusion targeted biopsy to pinpoint focal lesions. A day before the procedure, patients receive an intravenous infusion, so the gold nanoshells circulate for approximately 24 hours. That’s how we build up the nanoshells within the tumors. The following day, we use MRI-US fusion technology to target specific areas in the prostate. Multiple laser trochars are placed through a grid that allows us to stereotactically place laser fibers into the tumors. Laser energy is administered to the nanoshells for about 3 minutes. The patient goes home the same day. A few days later, we get an MRI scan to make sure the predicted ablation zone is the same as the actual ablation zone. The entire procedure takes about 2 hours.

Question 4. What were the major findings?

Answer
We reported results from the first 16 of 45 patients treated with the technique. The patients had had low- to intermediate-risk prostate tumors. We observed no adverse events. No patients leaked urine or reported erectile dysfunction. Patients tolerated it well. No patient required narcotics following the procedure. One patient had his follow-up MRI scan 2 days after the procedure and then drove to Florida. At 3 months, most patients showed a 42% reduction in PSA level. At 1 year, 87.5% of lesions that we ablated showed no signs of cancer. Our trial was the first to test nanomedicine-based photothermal ablation therapy in humans.

Question 5. How does your procedure compare with other ablative therapies for prostate cancer?

Answer
Other ablative technologies such as cryoablation, which creates a wide ablation zone, and laser interstitial thermal therapy, in which laser energy directly heats up tissue, are not tumor specific and thus are more likely to result in adverse effects.

Question 6. Where does the research go from here?

Answer
The next step for us is finishing the pivotal trial, which will include a total of a hundred patients enrolled at 6 sites. That will take us to the point at which the company will seek indication from FDA for prostate ablation.