No abstract

BACKGROUND: Localized prostate cancer can be treated several different ways, but head-to-head comparisons of treatments are infrequent. The authors of this report conducted a randomized, unblinded, noninferiority trial to compare cryoablation with external beam radiotherapy in these patients. METHODS: From December 1997 through February 2003, 244 men with newly diagnosed localized prostate cancer were assigned randomly to receive either cryoablation or radiotherapy (122 men in each arm). All received neoadjuvant antiandrogen therapy. The primary endpoint was disease progression at 36 months based on a trifecta definition: 1) radiologic evidence of metastatic disease, or 2) initiation of further antineoplastic therapy, or 3) biochemical failure. Two definitions of biochemical failure were used: 1) 2 consecutive rises in prostate-specific antigen (PSA) with a final value >1.0 ng/mL, and 2) a rise above PSA nadir þ 2 ng/mL. Secondary endpoints included overall survival, disease-specific survival, and prostate biopsy at 36 months. RESULTS: The median follow-up was 100 months. Disease progression at 36 months was observed in 23.9% (PSA nadir þ 2 ng/mL, 17.1%) of men in the cryoablation arm and in 23.7% (PSA nadir þ 2 ng/mL, 13.2%) of men in the radiotherapy arm. No difference in overall or disease-specific survival were observed. At 36 months, more patients in the radiotherapy arm had a cancer-positive biopsy (28.9%) compared with patients in the cryoablation arm (7.7%). CONCLUSIONS: The observed difference in disease progression at 36 months was small, 0.2%; however, because of the wide confidence interval, from À10.8% to 11.2%, it was not possible to rule out inferiority (defined a priori as a 10% difference). With longer term follow-up, the trend favors cryoablation. Significantly fewer positive biopsies were documented after cryoablation than after radiotherapy. Cancer 2010;116:323-30.

No abstract

No abstract

No abstract

A time dependent three-dimensional finite difference model of iceball formation about multiple cryoprobes has been developed and compared to experimental data. Realistic three-dimensional probe geometry is specified and the number of cryoprobes, the cryoprobe cooling rates, and the locations of the probes are arbitrary inputs by the user. The simulation accounts for observed longitudinal thermal gradients along the cryoprobe tips. Thermal histories for several points around commercially available cryoprobes have been predicted within experimental error for one, three, and five probe configurations. The simulation can be used to generate isotherms within the iceball at arbitrary times. Volumes enclosed by the iceball and any isotherms may also be computed to give the ablative ratio, a measure of the iceball's killing efficiency. This ratio was calculated as the volume enclosed by a critical isotherm divided by the total volume of the iceball for assumed critical temperatures of -20 and -40 degrees C. The ablative ratio for a single probe is a continuously decreasing function of time but when multiple probe configurations are used the ablative ratio increases to a maximum and then essentially plateaus. Maximum values of 0.44 and 0.55 were observed for three and five probe configurations, respectively, with an assumed critical temperature of -20 degrees C. Assuming a critical temperature of -40 degrees C, maximum ablative ratios of 0.21 and 0.3 for three and five probe configurations, respectively, were observed.

X-ray CT is able to image the internal architecture of frozen tissue. Phantoms of distilled water, a saline-gelatin mixture, lard and a calf liver-gelatin suspension cooled by a plastic tube acting as a long liquid nitrogen cryoprobe were used to study the relationship between Hounsfield unit (HU) values and temperature. There is a signature change in HU value from unfrozen to completely frozen tissue. No discernible relation exists between temperature in a completely frozen tissue and its HU value for the temperature range achieved with commercial cryoprobes. However, such a relation does exist in the typically narrow region of phase change and it is this change in HU value that is the parameter of concern for quantitative monitoring of the freezing process. Calibration of temperature against change in HU value allows a limited set of isotherms to be generated in the phase change region for direct monitoring of iceball growth. The phase change temperature range, mid-phase change temperature and the absolute value of HU change from completely frozen to unfrozen tissue are shown to be sensitive to the medium. Modelling of the temperature distribution within the region of completely frozen phantom using the infinite cylinder solution to the Fourier heat equation allows the temperature history of the phantom to be predicted. A set of isotherms, generated using a combination of thermal modelling and calibrated HU values demonstrates the feasibility of routine x-ray CT assisted cryotherapy. Isotherm overlay will be a major aid to the cryosurgeon who adopts a fixed target temperature as the temperature below which there is a certainty of ablation of the diseased tissue.

Despite improvements in treatment of localized prostate cancer, local recurrence remains a significant problem. A total of 46 patients with proven local cancer recurrence following external beam radiotherapy entered a prospective clinical trial using ultrasound-guided cryosurgery to ablate the residual prostate gland. Persistent complications included one urethra-rectal fistula, incontinence (2), retention (3), and treatment induced erectile dysfunction (7). Using the PSA definitions for biochemical failure as PSA X0.3 ng/ml, the Kaplan-Meier plots showed the incidence of patients to be free of biochemical recurrence at 51 and 44% at 1 and 2 y, respectively. For a PSA X1.0, the values at 1 and 2 y were 72 and 58%.