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Prostate cancer: cryotherapy.

Abstract

The incidence of prostate cancer has more than doubled in the last 10 years, and 220,900 new cases will be detected in 2003. This increase is due in large part to increased use of prostate-specific antigen (PSA)-based screening, transrectal ultrasonography, and random biopsy of the prostate. The treatment of prostate cancer, however, remains controversial, and no consensus has been established as to what constitutes appropriate treatment for any stage of disease, especially for localized cancers. Radical prostatectomy, radiation therapy, or watchful waiting all have their advocates, and the risks and benefits of these approaches are discussed frequently. Skepticism about conventional treatments has stimulated patients and physicians to search for alternatives that are effective and associated with limited morbidity. Technologic developments have rekindled interest in cryotherapy as a viable alternative to other, more conventional localized therapies. Given the relative paucity of alternatives for patients who experience biochemical progression after radiotherapy, cryosurgery also may prove to be a good alternative for those patients whose tumors appear to remain localized despite progression. In addition, it appears that cryosurgery will play an increased role in the future management of prostate cancer.

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BibTeXRIS

Katsuto Shinohara. 2003. Prostate cancer: cryotherapy.. https://doi.org/10.1016/s0094-0143(03)00065-x

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Current status of HIFU and cryotherapy in prostate cancer--a review.

OBJECTIVES: To evaluate the current status of high-intensity focused ultrasound (HIFU) and cryosurgery as the primary treatment option in patients with prostate cancer. METHOD: A MedLine search using specified search terms was done on February 28, 2005. This search rendered 150 papers related to HIFU and 566 papers related to cryosurgery. Very few of these papers presented original outcome data and are included in the present review. RESULTS: No controlled trial was available for analysis, and no survival data were presented. No validated biochemical, surrogate end point was available for any of the two therapies. HIFU showed progression-free survival (based on prostate-specific antigen+/-biopsy data) of 63-87% (projected 3- to 5-yr data), but median follow-up in the studies ranged from 12-24 mo. Negative postoperative biopsies was seen in 82-94% of patients. Complications have been reduced by the combination of transurethral resection of the prostate and HIFU. Cryosurgery showed a progression-free survival of 36-92% (projected 1-7 yr data), depending on risk groups and definition of failure. Negative biopsies were seen in 72-87%, but no biopsy data were available for the currently used third-generation cryotherapy machines. Complications seem to be lower with the third-generation machines. CONCLUSIONS: None of the evaluated therapies has enough data available to support their use as an alternative to established therapies (surgery, radiation) for localised prostate cancer. Until further data become available, the use of both treatments should be restricted to patients unfit for established therapies who still have the need for local therapy.

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Thermal and flow measurements of continuous cryogenic spray cooling.

The performance of single sprays for high heat flux cooling using R-134a was studied. The heat flux and heat transfer coefficient at the surface of a sprayed jet based on measurements of steady-state temperature gradients on a thin copper plate during continuous spraying. Meanwhile, the spray droplets flow characteristics was also quantified through laser doppler velocimetry (LDV) measurements to obtain the local velocity distributions. The effects of mass flow rate and average droplet velocity, and spray exit-to-target distance on the surface heat flux including the corresponding critical heat flux (CHF) were explored through three different nozzle diameters of 0.2, 0.3, and 0.4 mm. Finally, the effective use of the fluid being delivered based on the cooling efficiency and cooling effectiveness was also examined. The relationship between CHF and nozzle performance in terms of cooling efficiency and cooling effectiveness was found. The heat transfer removal rate can reach up to 140 W/cm(2) for the present nozzle size of d (j)=0.2 and 0.3 mm, which may enhance the current cryogen spray cooling (CSC) technique that assists laser therapy of dermatoses.

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