Recently, third-generation cryosurgery has been widely introduced into clinical practice using argon-driven, ultrathin 17-gauge cryoprobes in accordance with the Joule-Thompson principle.[1-3] Contemporary cryosurgery includes these technologic advances along with the routine utilization of ultrathin needles incorporating a thermal monitoring system (TMS) for temperature surveillance, transrectal ultrasound (TRUS) imaging, and a urethral warming catheter to minimize morbidity associated with the procedure.[4-7] These developments allow for accurate targeting of even small solitary lesions that can aid in focal cryoablation of prostate cancer.
This review highlights trends in cryotechnique development, basic cryobiology, and primary whole-gland cryoablation including a recent trend toward organ-sparing procedures such as hemiablation and focal targeted cryoablation.
Advances in Cryotechnology and Cryobiology
Refining Cryoneedles and Temperature Monitoring
Gowardhan et al recently presented experimental testing in an in vitro phantom prostate model and subsequent clinical study of 20 prostate cancer patients. These patients were treated with cryoablation using new developments in third-generation cryotechnology such as the IceRodTM (Oncura, Amersham, UK) 17-gauge cryoneedles with an advanced heat exchanger and the MultitempTM 1601 TMS (InvivoSense, Trondheim, Norway).
The IceRodTM probes demonstrated a better ability to freeze tissue reaching lower temperatures and forming iceballs with a maximum diameter > 6 cm after freezing at full power for 10 minutes. In other words, these probes can be used in prostates measuring > 3.5 cm in sagittal length, obviating the need for a “pull-back” technique sometimes required when using probes that generate smaller volumes of ice. TMS monitoring depicted real-time temperature gradients over either 4 or 8 temperature points arranged in linear gradients, suggesting that single-point temperature monitoring might not accurately depict the lowest critical temperatures reached during treatment when completely ablating tumor cells. These innovations may potentially improve cryosurgical technique and facilitate the procedure in a potentially safer, targeted, reproducible form, allowing beginners to learn the procedure more quickly and efficiently.
Baust et al presented an update of critical experimental and clinical issues regarding the successful clinical application of cryosurgical ablation for prostate cancer. These authors presented information on the molecular basis of tissue response to freezing, identifying apoptosis as a significant part of tumor destruction after cryoablation. This paper provides an excellent basic science foundation for translational research highlighting suggested improvements in the clinical implementation of this technique, such as optimization of the freeze cycle duration, optimization of target tissue temperature, and adjunctive combination of chemotherapy with cryotherapy.