Cryosurgery for prostate cancer: improved glandular ablation by use of 6 to 8 cryoprobes

Gold nanoshell-localized photothermal ablation of prostate tumors in a clinical pilot device study

Biocompatible gold nanoparticles designed to absorb light at wavelengths of high tissue transparency have been of particular interest for biomedical applications. The ability of such nanoparticles to convert absorbed near-infrared light to heat and induce highly localized hyperthermia has been shown to be highly effective for photothermal cancer therapy, resulting in cell death and tumor remission in a multitude of preclinical animal models. Here we report the initial results of a clinical trial in which laser-excited gold-silica nanoshells (GSNs) were used in combination with magnetic resonance-ultrasound fusion imaging to focally ablate low-intermediate-grade tumors within the prostate. The overall goal is to provide highly localized regional control of prostate cancer that also results in greatly reduced patient morbidity and improved functional outcomes. This pilot device study reports feasibility and safety data from 16 cases of patients diagnosed with low- or intermediate-risk localized prostate cancer. After GSN infusion and high-precision laser ablation, patients underwent multiparametric MRI of the prostate at 48 to 72 h, followed by postprocedure mpMRI/ultrasound targeted fusion biopsies at 3 and 12 mo, as well as a standard 12-core systematic biopsy at 12 mo. GSN-mediated focal laser ablation was successfully achieved in 94% (15/16) of patients, with no significant difference in International Prostate Symptom Score or Sexual Health Inventory for Men observed after treatment. This treatment protocol appears to be feasible and safe in men with low- or intermediate-risk localized prostate cancer without serious complications or deleterious changes in genitourinary function.

Targeted Ablative Therapies for Prostate Cancer

Men diagnosed with low- to intermediate-risk, clinically localized prostate cancer (PCa) often face a daunting and difficult decision with respect to treatment: active surveillance (AS) or radical therapy. This decision is further confounded by the fact that many of these men diagnosed, by an elevated PSA, will have indolent disease and never require intervention. Radical treatments, including radical prostatectomy and whole-gland radiation, offer greater certainty for cancer control, but at the risk of significant urinary and/or sexual morbidity. Conversely, AS preserves genitourinary function and quality of life in exchange for burdensome surveillance and the psychological impact of living with cancer.

Issues Critical to the Successful Application of Cryosurgical Ablation of the Prostate

The techniques of present-day cryosurgery performed with multiprobe freezing apparatus and advanced imaging techniques yield predictable and encouraging results in the treatment of prostatic and renal cancers. Nevertheless, and not unique to cryosurgical treatment, the rates of persistent disease demonstrate the need for improvement in technique and emphasize the need for proper management of the therapeutic margin. The causes of persistent disease often relate to a range of factors including selection of patients, understanding of the extent of the tumor, limitations of the imaging techniques, and failure to freeze the tumor periphery in an efficacious manner. Of these diverse factors, the one most readily managed, but subject to therapeutic error, is the technique of freezing the tumor and appropriate margin to a lethal temperature [Baust, J. G., Gage, A. A. The Molecular Basis of Cryosurgery. BJU Int 95, 1187–1191 (2005)]. This article describes the recent experiments that examine the molecular basis of cryosurgery, clarifies the actions of the components of the freeze-thaw cycle, and defines the resultant effect on the cryogenic lesion from a clinical perspective. Further, this review addresses the important issue of management of the margin of the tumor through adjunctive therapy. Accordingly, a goal of this review is to identify the technical and future adjunctive therapeutic practices that should improve the efficacy of cryoablative techniques for the treatment of malignant lesions.

Ultrasound Guided Combined Cryoablation and Microencapsulated 5-Fluorouracil Inhibits Growth of Human Prostate Tumors in Xenogenic Mouse Model Assessed by Luminescence Imaging

Modern approaches to minimally invasive ablative treatment of solid tumors involve the use of miniature instruments and combined treatments. These can be enhanced with ultrasound imaging that depicts tumor margins; facilitates guidance, delivery, and dosage of local chemotherapy; and can monitor the effectiveness of the treatment. This paper describes the advantages of ultrasound guided cryosurgery combined with local chemotherapy delivered in multilamellar, echogenic microcapsules of 5-FU (“μcaps”) using a xenograft tumor model. Genetically engineered bioluminescent human prostate tumor cells, DU-145Luc+, were implanted subcutaneously into athymic nude mice. Experiments were designed to mimic the situation where palliative cryoablation spares a portion of the tumor so that the combined effect of cryosurgery and focal injections of chemotherapeutic microcapsules could be evaluated. Eighteen (18) tumors were treated with percutaneous partial cryoablation or interstitial chemoablation, or a combination of both. A single F/T cycle was applied to tumor and micro-encapsulated chemotherapy is delivered at outer margin of frozen tumor in two opposite sites. Results show that the tumor and cryosurgical kill zone contours were seen with both the bio-luminescence assay (BLI) and ultrasonography (US). US can easily detect as little as 2 μl of echogenic μcaps, and monitor their lifetime in the tumor tissue. BLI was determinant in showing that minute amounts of microcapsule chemotherapy (38.7 ng of 5-FU/g tumor) dramatically inhibited tumor growth starting within two days after injection. The mean BLI emitted by control tumors was 5.6 times greater at Day 4 than the BLI measurements from tumors treated with 5-FU μcaps (p=0.036). By Day 7, BLI values from the control tumors were still 2.7 times greater than those treated with 5-FU μcaps (p<0.01). In tumors treated by partial cryoablation, the mean BLI of viable tumor cells was 20 times less at day 3 (p=0.05) and 46% less at day 7 than the non-treated tumors. The combined treatment produced a dramatic inhibition of tumor growth that lasted throughout the 7-day study. The BLI measured from viable tumor cells in non-treated tumors was 34 times greater at day 3 and more than 350 times greater at day 7 than those treated by combined cryoablation and 5-FU μcaps. The results demonstrated, for the first time, that a single moderate freeze of a human prostate tumor combined with bi-focal peripheral microcapsule chemotherapy (5-FU) has a better and longer inhibitory effect on tumor growth compared to the growth inhibition rendered by cryosurgery or local microcapsule chemo-therapy alone. This shows promise for a new, focal, combined ablative modality using US guided deposition of microencapsulated drug(s) and echogenic markers deposited in the hypothermic margin of tumors which could enhance the efficacy of cryoablation of prostate cancers.

Progress toward Optimization of Cryosurgery

Cryosurgery for diverse neoplastic and non-neoplastic diseases has expanded in applicability in recent years, especially since intraoperative ultrasound became available as a method of monitoring the process of tissue freezing. However, persistence of disease after presumably adequate cryosurgical treatment has disclosed deficiencies in the technique, perhaps due to faulty application of the freeze-thaw cycles or due to shortcomings in the imaging method. Clearly cryosurgical technique is less than optimal. The optimal dosimetry for tissue freezing, the recent improvements in imaging techniques, and the need for adjunctive therapy are defined in this review, which assesses the progress toward improving the efficacy of cryosurgery.

Cryosurgery for Tumors — A Clinical Overview

Cryosurgery, a method of treating disease by the production of freezing temperatures in the tissue, is a useful technique for the treatment of tumors. When the modern era of cryosurgery began in the mid 1960's, the technique was used only for tumors easily accessible by direct observation or via endoscopy, such as those of the skin, oral cavity, and prostate gland. In general, the technique had limited usefulness in the next two decades. However, with the advent of intraoperative ultrasound as a method of monitoring the process of freezing and with the development of more effective cryosurgical apparatus, the cryosurgical treatment of tumors of the viscera and other deep tissues became practical in the 1990's. This review assesses the present day status of cryosurgery in the management of diverse tumors.

In Treating Localized Prostate Cancer the Efficacy of Cryoablation is Independent of DNA Ploidy Type

While the prognostic value of DNA ploidy has been well established for radical prostatectomy, external beam radiation, brachytherapy and androgen deprivation therapy its role as a survival outcome predictor for prostate cancer patients treated with cryoablation has not yet been examined. Anecdotal evidence suggesting that cryoablation may be independent of DNA ploidy type led to the implementation of the current study. Retrospective analysis of data including flow digital cytometry was performed on 447 archival specimens taken from patients who had undergone cryosurgical ablation of primary prostate cancer. Five-year biochemical disease free survivals (bDFS) (defined as PSA thresholds of 0.5 and 1.0 ng/ml) were determined with Kaplan-Meier analysis. Patients were grouped according to DNA ploidy types then stratified by Gleason grade, risk group, pre-surgical PSA level, and disease stage.

Mean and median age of the cohort was 65 and 64.6 years. Mean follow-up was 65.7 months. The DNA ploidy status of the population was found to be 59% diploid, 13% tetraploid, and 28% aneuploid. Using PSA < 1.0 ng/ml criterion, the bDFS rates for diploid, tetraploid, and aneuploid were 78%, 75%, and 79% respectively. The bDFS rates using a PSA < 0.5 ng/ml criterion were 67%, 59%, and 69% for diploid, tetraploid, and aneuploid groups. No significant outcome differences were found in stratified analysis. This investigation demonstrates that the efficacy of cryoablation is independent of DNA ploidy type.

Salvage cryotherapy: is there a role for focal therapy?

Prostate cancer treatment has undergone vast development over the last few decades, but the most notable changes have included nerve-sparing open radical prostatectomy, laparoscopic radical prostatectomy, including robot-assisted and, more recently, cryotherapy and high-intensity focused ultrasound (HIFU). While radical surgery is the current gold standard, the less invasive therapeutic options of cryotherapy and HIFU are regarded as largely experimental by governing bodies. In the case of cryotherapy, a wealth of experience has been accumulated demonstrating its efficacy. Initially used as a salvage treatment for radiation-failed prostate cancer, cryotherapy has been widely used as a primary treatment for localized and locally advanced prostate cancer. More recently, there has been interest expressed in the concept of focal therapy in prostate cancer. This has been evaluated as a primary treatment for prostate cancer, but little information is available regarding the potential use as a salvage treatment. In this article, we evaluate the potential for focal treatment in the salvage setting.

Thermal ablation of prostate diseases: advantages and limitations

Both benign and malignant conditions affecting prostate gland are very common in elderly men. However, the conventional treatment of these conditions can be associated with significant side effects and complications, and less invasive treatment alternative has been always searched for. Because of the anatomical location and easy accessibility of prostate, many newer treatment modalities using thermal ablation have been applied to the organ. These include not only heating of the pathological tissue but also freezing. Some of such treatment techniques have shown to be effective and safe and been clinically used widely. In this review article, various tissue ablation techniques using temperature change applied to prostate gland are covered. Each procedure's advantages and disadvantages are compared and discussed.

Prostate cryotherapy monitoring using vibroacoustography: preliminary results of an ex vivo study and technical feasibility

The objective of this research is to prospectively evaluate the feasibility of vibroacoustography (VA) imaging in monitoring prostate cryotherapy in an ex vivo model. Baseline scanning of an excised human prostate is accomplished by a VA system apparatus in a tank of degassed water. Alcohol and dry ice mixture are used to freeze two prostate tissue samples. The frozen prostates are subsequently placed within the water tank at 27 degrees C and rescanned. VA images were acquired at prescribed time intervals to characterize the acoustic properties of the partially frozen tissue. The frozen prostate tissue appears in the images as hypoemitting signal. Once the tissue thaws, previously frozen regions show coarser texture than prior to freezing. The margin of the frozen tissue is delineated with a well-defined rim. The thawed cryolesions show a different contrast compared with normal unfrozen prostate. In conclusion, this pilot study shows that VA produces clear images of a frozen prostate at different temperature stages. The frozen tissue appears as a uniform region with well-defined borders that are readily identified. These characteristic images should allow safer and more efficient application of prostatic cryosurgery. These results provide substantial motivation to further investigate VA as a potential modality to monitor prostate cryotherapy intraoperatively.

Single center experience with third-generation cryosurgery for management of organ-confined prostate cancer: critical evaluation of short-term outcomes, complications, and patient quality of life

BACKGROUND AND PURPOSE

Technical refinements such as improved ultrasonographic localization and the routine use of urethral warmers and small-gauge needle delivery systems have renewed interest in cryosurgical treatment as a minimally invasive option for selected patients with localized prostate cancer. Only three reports of quality of life (QoL) in prostate cryoablation exist, and none report on patients treated with third-generation cryoablative technology. We critically examine our initial series of consecutive patients at a single institution undergoing primary third-generation cryosurgical treatment of localized prostate cancer with respect to treatment outcome, morbidity profile, and QoL parameters. To our knowledge, this is the first QoL report on third-generation cryoablation of the prostate.

PATIENTS AND METHODS

We retrospectively review the records of 89 consecutive patients with median followup of 11 months (1-32) who have undergone third-generation cryosurgical ablation of the prostate as primary treatment for localized prostate cancer with intention to cure. Patients were risk stratified according to preprocedural parameters of prostate-specific antigen (PSA), clinical stage, and Gleason score. PSA trends were recorded and treatment effectiveness was observed using different definitions of biochemical failure. Charts were reviewed for postprocedure complications. Quality of life was measured prospectively using the University of California, Los Angeles, Prostate Cancer Index as well as American Urological Association symptom scores. We compare a percent of baseline score (%BS) for various domains between our series of patients treated with primary cryoablation with a series of patients undergoing brachytherapy for localized prostate cancer.

RESULTS

Treatment success was defined by achievement of a PSA nadir of < or =0.1 ng/mL and by biochemical disease-free survival (BDFS) assessed with both a PSA threshold of < or =0.4 ng/dL over time and the American Society for Therapeutic Radiology and Oncology (ASTRO) definition of three consecutive rises in PSA. According to risk stratification, 86%, 81.5%, and 78% of low-, intermediate-, and high-risk patients, respectively, achieved a PSA nadir of < or =0.1 ng/mL. Overall, at 12 months follow-up, 94% of patients achieved BDFS using ASTRO criteria while 70% achieved BDFS using a PSA threshold of < or =0.4 ng/mL. With risk stratification, 74%, 70%, and 60% of low-, intermediate-, and high-risk patients, respectively, achieved BDFS defined by PSA threshold of < or =0.4 ng/mL. Complications were rare. The response rate for Health Related Quality of Life (HRQoL) questionnaires was 71% for cryoablation patients and 51% for brachytherapy patients. At 12 months follow-up, patients undergoing cryoablation on average achieved urinary and bowel domain scores comparable to baseline, but sexual domains remained well below baseline. When compared with a brachytherapy series with better baseline sexual function (P = 0.04) and urinary function (P = 0.03), cryotherapy patients experienced more negative impact on sexual function steadily for up to 12 months (P = 0.02). Urinary function was similar between the groups until 18 months, at which time cryoablation patients fared better (P = 0.01); this was sustained up to 24 months (P = 0.04).

CONCLUSIONS

Treatment success with cryosurgery varies with definition; however, our results are comparable to other series with regard to short-term cancer control. Complication rates in this series of third-generation cryosurgical patients are low. QoL characteristics of third-generation cryoablation are similar to those described in second-generation cryoablation series. Compared with brachytherapy, cryotherapy results in less irritative and obstructive voiding symptoms in the early post-treatment period and may improve urinary function up to 24 months after treatment. In a small group of older patients with baseline erectile dysfunction undergoing cryoablation, sexual function returns to 20% of its baseline value with up to 12 months follow-up.

Review of primary and salvage cryoablation for prostate cancer

BACKGROUND

Cryosurgery has gained popularity as a minimally invasive treatment option for primary and recurrent prostate cancer. Herein we present a review and summary reports on primary cryoablation for prostate cancer and salvage cryoablation following radiation failure.

METHODS

We reviewed the current published literature in the English language on these topics, along with some historic articles dating back to the 1960s for background and development of the procedure. The material is supplemented by some commentary based on our own 13-year experience with cryoablation for prostate cancer. The review is divided into two sections: primary and salvage cryoablation.

RESULTS

For primary cryoablation, success rates are proportional to the risk categories of the primary cancers. A pretreatment prostate-specific antigen (PSA) <or= 10 ng/mL and an undetectable PSA nadir following cryoablation are associated with a more favorable long-term outcome. Safety profile and quality of life are acceptable in carefully selected patients. Similarly, for salvage cryoablation following radiation failure, patient selection is of paramount importance. The most consistently identified predictive factors for poor cryoablation outcomes were pre-cryoablation PSA > 10 ng/mL and post-cryoablation nadir PSA > 1 ng/mL for salvage procedures. Side effects are more prevalent and serious than with primary cryoablation but for carefully selected patients, the long-term results are favorable.

CONCLUSIONS

Patient selection is the key to success with cryoablation, in both the primary and salvage setting. The modality can offer long-term cancer control in carefully selected patient with properly executed techniques.

Cryosurgical technique: assessment of the fundamental variables using human prostate cancer model systems

Cryosurgery offers a promising therapeutic alternative for the treatment of prostate cancer. While often successful, complete cryoablation of cancerous tissues sometimes fails due to technical challenges. Factors such as the end temperature, cooling rate, duration of the freezing episode, and repetition of the freezing cycle have been reported to influence cryosurgical outcome. Accordingly, we investigated the effects of these variables in an in vitro prostate cancer model. Human prostate cancer PC-3 and LNCaP cultures were exposed to a range of sub-zero temperatures (-5 to -40 degrees C), and cells were thawed followed by return to 37 degrees C. Post-thaw viability was assessed using a variety of fluorescent probes including alamarBlue (metabolic activity), calceinAM (membrane integrity), and propidium iodide (necrosis). Freeze duration following ice nucleation was investigated using single and double freezing cycles (5, 10, and 20 min). The results demonstrated that lower freezing temperatures yielded greater cell death, and that LNCaP cells were more susceptible to freezing than PC-3 cells. At -15 degrees C, PC-3 yielded approximately 55% viability versus approximately 20% viability for LNCaP. Double freezing cycles were found to be more than twice as destructive versus a single freeze-thaw cycle. Both cell types experienced increased cell death when exposed to freezing temperatures for longer durations. When thawing rates were considered, passive (slower) thawing following freezing yielded greater cell death than active (faster) thawing. A 20% difference in viability between passive and active thawing was observed for PC-3 for a 10 min freeze. Finally, the results demonstrate that just reaching -40 degrees C in vitro may not be sufficient to obtain complete cell death. The data support the use of extended freeze times, multiple freeze-thaw cycles, and passive thawing to provide maximum cell destruction.

Cryotherapy for localised prostate cancer

BACKGROUND

Prostate cancer is a common cancer in elderly men and in some will prove fatal. Standard treatments for localised disease include surgery ( radical prostatectomy), radiotherapy and active monitoring. New emerging therapies are being evaluated with the aim of reducing the complication rate associated with standard therapies, as well as developing an effective treatment. One such modality is cryotherapy, a procedure that introduces probes directly into the prostate tumour and kills the malignant cells by a freezing process.

OBJECTIVES

This review aims to evaluate the relative clinical and economic benefits of cryotherapy compared to standard therapies for the primary treatment of localised prostate cancer.

SEARCH STRATEGY

Our search strategy included an electronic search of MEDLINE from 1996 to December 2006, plus EMBASE (Excerpta Medica Database), the Cochrane library, ISI Science Citation Index, Database of Abstracts and Reviews of Effectiveness (DARE), and LILACS to identify all relevant published randomised trials of cryotherapy for localised prostate cancer. Cancerlit and HealthSTAR databases were searched to their final date. Handsearching of relevant journals was undertaken.

SELECTION CRITERIA

Only published randomised trials comparing the effectiveness of cryotherapy with radical prostatectomy, radiotherapy or active monitoring for the primary treatment of men with localised prostate cancer were eligible for inclusion in this review.

DATA COLLECTION AND ANALYSIS

Data were extracted from eligible studies, and included study design, participants, interventions and outcomes. Primary outcome measures were biochemical disease-free survival, disease-free survival and treatment-induced complications. Secondary outcomes included disease-specific survival, overall survival, quality-of-life outcome measures and economic impact measures.

MAIN RESULTS

There were no randomised trials found comparing cryotherapy with other therapies for the primary treatment of localised prostate cancer. All studies identified were case series. To indicate the level of the available evidence, studies that evaluated cryotherapy as a primary therapy, using transrectal ultrasound guidance and urethral warming in at least 50 patients with localised prostate cancer, and a minimum of one year follow up, were reviewed. Eight case series were identified that complied with these criteria; two were retrospective. The patients recruited (n = 1483) had an age range from 41 to 84 years, stages T1 = 0 to 43%, T2 = 24 to 88%, T3 = 1 to 41%, and T4 = 0 to 14%. The mean preoperative PSA level ranged from 9.7 to 39 ng/mL, with Gleason scores < 7 and ranging from 6 to 37%. One additional study that compared cryotherapy (total cryotherapy and standard cryotherapy with urethral preservation) with radical prostatectomy was also identified and reviewed. In this study the success rates, defined as a post-treatment PSA of 0.2 ng/mL or less, were reported as 96% for total cryotherapy, 49% for standard cryotherapy and 73% for radical prostatectomy. Four studies did not monitor the temperature of the cyro-procedure and reported 17 to 28% of patients had a positive biopsy following cryotherapy with a mean PSA nadir of 0.55 to 1.75 ng/mL (median 0.4 to 1.85 ng/mL). The other four studies used thermocouples to monitor the temperature of the cryo-procedure and reported progression-free survival rates of 71 to 89% with 1.4 to 13% of patients having a positive biopsy post-cryotherapy. At 5 years, overall survival was reported as 89 to 92% in two studies, and disease-specific survival as 94% in one study. The major complications observed in all studies included impotence (47 to 100%), incontinence (1.3 to 19%), and urethral sloughing (3.9 to 85%), with less common complications of fistula (0 to 2%), bladder-neck obstruction (2 to 55%), stricture (2.2 to 17%) and pain (0.4 to 3.1%). Most patients were sent home the following day (range 1 to 4 days).

AUTHORS' CONCLUSIONS

Cryotherapy offers a potential alternative to standard therapies for the primary treatment of localised prostate cancer. However, the poor quality of the available studies makes it difficult to determine the relative benefits of this modality. Randomised trials are needed to fully evaluate the full potential of cryotherapy in men with this disease. Patients selecting cryotherapy as their therapeutic option should be made fully aware of the reported efficacy, complications and the low-grade evidence from which these data are derived.

Ultrasound probe positioning to minimize the risk of recto-urethral fistula during cryosurgical ablation of prostate cancer

OBJECTIVE

To evaluate the ability to increase the distance between the rectal mucosa and prostate, and thus decrease the risk of recto-urethral fistula, and to improve the ability to adequately freeze beyond the prostatic capsule during cryosurgical ablation for prostate cancer.

PATIENTS AND METHODS

The transrectal ultrasound probe was manipulated to increase the distance from the rectal mucosa to prostate in 28 men scheduled for cryosurgical ablation for localized prostate cancer. Ten patients were treated for local recurrence after previous definitive radiotherapy, and cryosurgery was chosen as the primary treatment for the remainder.

RESULTS

The mean (range) distance from the rectal mucosa to the prostate when the probe was securely applied to the rectal wall was 2.5 (1-7) mm, and could be extended to 9.6 (7-14) mm before the ultrasonogram quality diminished enough to impede accurate placing of the cryoprobe. The mean distance gained as a margin of error was 7.1 (4-12) mm (P < 0.001). In no patient was it felt that visualization during the freezing cycles was impaired. No recto-urethral fistula was identified.

CONCLUSION

The manoeuvres described here allow the surgeon to freeze beyond the prostatic capsule while maintaining a visible distance from rectal wall. The extra distance created by this manoeuvre might reduce the risk of recto-urethral fistula, and potentially improve tumour control in the posterior aspect of the prostate, based on the ability to freeze beyond the capsule to reach lethal temperatures in all prostatic tissue.

Cryoablation as Primary Treatment for Localized Prostate Cancer Followed by Penile Rehabilitation

OBJECTIVES

To determine the medium term efficacy and morbidity of patients who underwent cryoablation as primary therapy for localized prostate cancer followed by a penile rehabilitation regimen.

METHODS

Patients were treated with whole gland cryoablation. Those potent at intervention were encouraged to use a vacuum erection device regularly after treatment. Incontinence was defined as any leakage of urine. Potency was defined as the ability to achieve an erection sufficient to complete intercourse with or without oral pharmaceutical agents. Biochemical failure was defined as three successive rises in prostate-specific antigen, with a final value greater than 1.0 ng/mL.

RESULTS

A total of 416 consecutive patients were treated. The mean patient age was 69.4 years, mean prostate-specific antigen level was 8.7 ng/mL, median Gleason score was 6, and median stage was T1c. The mean follow-up of the entire population was 20.4 +/- 14.7 months. Of those continent before treatment, 4.0% were incontinent at 6 months but only 2 (0.6%) used any absorbent pads. Kaplan-Meier analysis demonstrated progressive recovery of sexual function of preoperatively potent men, with 41.4% +/- 4.3% and 51.3% +/- 5.9% potent 1 and 4 years after treatment, respectively. No patients had rectal fistula. The actuarial probability of remaining biochemically disease free at 4 years was 79.6% +/- 2.4%, with a mean time to failure of 4.2 months. After therapy, 168 patients underwent biopsy; 17 had positive findings (10.1%). The positive biopsy rate for the entire population was 4.1% (17 of 416).

CONCLUSIONS

The results of our study have indicated that cryoablation as a primary treatment of localized prostate cancer is effective with acceptable morbidity. The use of a penile rehabilitation regimen after treatment appeared to substantially increase postcryoablation potency.

Salvage Cryosurgery for Recurrent Prostate Carcinoma after Radiotherapy

Cryotherapy is a salvage treatment for patients with biopsy-proved prostatic adenocarcinoma recurrent after radiotherapy. Proper sampling, labeling, and analysis of prostate biopsies allows prompt diagnosis, identification of important prognostic parameters, and planning of an appropriate therapeutic strategy. Whereas androgen-suppressive therapy is associated with only a temporary benefit, transperineal salvage cryosurgery offers a potentially curative option for patients with localized disease, even those with significant comorbidities. Technological advances, including computerized treatment planning and miniaturized cryoprobes, may provide further therapeutic advantages and lower complication rates. Cryotherapy should be included among the established therapeutic options for recurrence after radiotherapy.

Laser-assisted cryosurgery of prostate: numerical study

A new methodology for preventing freezing damage beyond pre-specified boundaries during prostate cryosurgery is proposed herein. It consists of emitting controlled laser irradiation from the urethra, across the wall and into the prostate while conventional cryoprobes freeze the unwanted prostate tissue. The purpose of this methodology is to protect the urethral wall better and confine the desired cryoinjured region more accurately than the current cryosurgery approach. We also explore the potential use of light-absorbing dyes to further enhance the laser light absorption and corresponding heat generation to increase the thickness of the protected region. A finite difference heat diffusion model in polar coordinates with temperature-dependent thermophysical properties simulates the prostate freezing while laser irradiation across the urethral wall is emitted. This approach maintains the temperature of the urethral wall and the adjacent tissue above a pre-specified threshold temperature of -45 degrees C, independent of application time. Temperature contours resulting from prostate cryoablation with (a) conventional constant temperature heating; (b) laser irradiation heating; and (c) laser irradiation heating with pre-injected light-absorbing dye layers indicate that the thickness of the protected region increases in this order, and that the latter two methodologies may be more effective in limiting cryoinjury to a predefined region compared to constant temperature heating. An analysis of laser power requirements and sensibility of laser-assisted cryosurgery (LAC) of prostate is also presented. It is shown that tissue temperature may vary as much as +/-20 degrees C with variations of +/-10% in laser power relative to the nominal power required to maintain the tissue at 37 degrees C. This demonstrates the sensitivity to laser power and the need of an accurate laser power control algorithm.

Update on cryotherapy for prostate cancer in 2006

PURPOSE OF REVIEW

With the recent introduction of novel, minimally invasive procedures for the treatment of prostate cancer, cryotherapy has become a feasible option as a viable alternative to traditional radical surgery and radiation therapy. In this review we update recent data concerning the basic science of cryobiology, technical trends, oncologic results and complications of this procedure.

RECENT FINDINGS

As a result of better understanding of tumor cryodestruction at a molecular level, refinements in cryotechniques and improved patient selection, the results of cryotherapy are becoming more promising. Furthermore, the dramatic decrease in the number of complications after modern cryotherapy leads to a better quality of life, which may be a preferable option, especially for elderly patients with comorbidities. Current trends towards nerve-sparing and focal cryoablation are also discussed. Recent advances in cryobiology open up new opportunities to apply cryotherapy in combination with chemotherapy or radiotherapy for patients with intermediate or high-risk cancers.

SUMMARY

Potential directions for future developments in cryosurgery include concepts to reduce side effects such as minimizing cryodamage of the neurovascular bundles (nerve-sparing procedure), and focal ablation of a specific tumor site in patients in whom saturation biopsy supports unifocal prostate cancer.

Feasibility of nerve-sparing prostate cryosurgery: applications and limitations in a canine model

BACKGROUND AND PURPOSE

In a canine model, we evaluated the feasibility of nerve-sparing cryosurgery by active warming of the neurovascular bundle (NVB). Furthermore, our aim was to determine if NVB warming increases the risk of acinar gland and stromal-tissue preservation in adjacent areas of the prostate. The effects of a single versus double freeze-thaw cycle on prostate tissue were also assessed.

MATERIALS AND METHODS

Ten prostate lobes from five dogs were evaluated. Nine lobes from five dogs were treated with cryoablation using 17-gauge gas-driven cryoneedles. Seven lobes wre treated with active warming of the NVB using helium gas, and two lobes were treated without active warming. A single or double freeze-thaw cycle was utilized. Prostate tissue ablation and NVB preservation were evaluated in histologic sections.

RESULTS

All seven prostate lobes treated with active warming demonstrated complete or partial NVB preservation. Four of these lobes had adjacent gland preservation. All lobes treated with a double freeze-thaw cycle showed complete and uniform ablation of prostate tissue. One of the three lobes treated with a single freeze-thaw cycle demonstrated incomplete ablation of the tissue.

CONCLUSIONS

This is the first study investigating the feasibility of NVB preservation under controlled experimental conditions. In our canine model, NVB preservation with active warming was possible but not consistently reproducible. In some cases, NVB preservation with active warming may result in incomplete peripheral tissue ablation. A double, but not a single, freeze-thaw cycle induces complete and effective necrosis of prostatic tissue. These results have significant clinical applications when attempting nerve-sparing cryosurgical ablation of the prostate.

Transperineal Salvage Cryosurgery (SC) for Prostate Adenocarcinoma

Criteria used for the diagnosis and treatment of recurrent prostate adenocarcinoma after radiotherapy are examined according to recently published studies in the literature. The diagnosis of recurrence is confirmed by the histological test of a biopsy performed due to the gradual increase in prostate-specific antigen (PSA). Proper sampling, nomenclature and analysis of prostate biopsies allow an early diagnosis to identify some important prognostic parameters and to plan the most appropriate therapeutic strategy for every single case. Androgen suppressive therapy only induces a temporary benefit in these patients. Transperineal salvage cryosurgery (SC) represents a recognized effective treatment option. Technological advances, including computerized treatment planning and miniaturized cryoprobes, allow further potential therapeutic advantages and reduce complications. Results of SC are promising even in patients with other comorbidities; therefore, it is useful to include it among therapeutic instruments for failures following radiotherapy.

CURRENT STATUS OF LOCAL SALVAGE THERAPIES FOLLOWING RADIATION FAILURE FOR PROSTATE CANCER

PURPOSE

We reviewed the curative options available to patients with local failure after radical radiotherapy for prostate cancer and identified the patients best suited for such salvage therapies.

MATERIALS AND METHODS

A literature search of English language publications was done using the key terms salvage, prostatectomy, cryosurgery, brachytherapy and radiation failure.

RESULTS

Salvage radical prostatectomy offers 5-year biochemical relapse-free rates between 55 and 69%. Higher complication rates are reported with salvage compared to primary radical prostatectomy, including rectal injuries, bladder neck contracture and urinary incontinence. Cryosurgery biochemical response rates vary according to the definition of failure but they are generally lower than those of salvage radical prostatectomy. The local control rates of cryosurgery are acceptable. Major complications related to cryotherapy are urinary incontinence, impotence, pelvic pain and urinary retention. Experience with salvage brachytherapy has been limited but some success has been reported in terms of biochemical control.

CONCLUSIONS

Salvage prostatectomy for localized radiation failure is a good option in the patient with a life expectancy of at least 10 years, preradiation and preoperative prostate specific antigen less than 10 ng/ml, and localized preoperative stage with the understanding that complication risks are higher. Salvage cryotherapy is a valid option in patients with preoperative prostate specific antigen less than 10 ng/ml and Gleason score less than 8, clinical stage less than T3 who are hormonally naive. Salvage cryotherapy is especially suited for older patients with some comorbidities who are still considered to be at reasonable anesthetic risk. The study of brachytherapy remains in its infancy and the efficacy of this modality remains to be determined.

Addition of anticancer agents enhances freezing-induced prostate cancer cell death: implications of mitochondrial involvement

Recent evidence suggests that the successful treatment of prostate cancer may require adjuvant therapies. Accordingly, a better understanding of the molecular mechanisms involved in current treatments may lead to enhanced efficacy by providing a basis for adjuvant therapies. In this study, we demonstrate that the combination of sub-lethal concentrations of chemotherapeutic agents prior to freezing (-15 degrees C) in a prostate cancer cell (PC-3) model results in enhanced efficacy over either treatment alone. Morphological analysis revealed that necrosis appeared to be the prevalent mode of cell death following adjuvant (in vitro) modeling, yet molecular analysis indicated that freezing and chemotherapy differentially activated apoptotic cascades through modulating opposing members of the Bcl-2 protein family. Freezing results in a time-dependent increase of the antiapoptotic Bcl-2 protein, while chemotherapy results in an increase of the pro-apoptotic Bax protein. Anti-apoptotic Bcl-2 protein levels increase over 3-fold following exposure to freezing. 5-Fluorouracil (5-FU) causes pro-apoptotic Bax levels to increase 2-fold during the drug exposure. The increase in Bax was also apparent following the combination of 5-FU/freezing, while Bcl-2 levels were maintained at or below control levels. This led to a shift in the Bcl-2 to Bax ratio to a pro-death tendency. Other effective cryo/chemo combinations were also found to provide similar effects. The combination of cisplatin/freezing resulted in a 4-fold increase in the ratio of Bax to Bcl-2 when compared to controls, which represented a 2-fold increase over the 5-FU/freezing-combination model. This increase may contribute to the continued reduction in cell number observed during the 13-day recovery period. Additionally, the addition of an apoptotic caspase inhibitor was not able to protect cultures from cell death following combination treatment. In conclusion, the data suggest that both Bcl-2 and Bax may, not only, play an important role in the efficacy of the cryo/chemo combination, but also the balance between the two may determine the role and extent of system destruction.

Prostate cancer: cryotherapy

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.

Incomplete glandular ablation after salvage cryotherapy for recurrent prostate cancer after radiotherapy

PURPOSE

To determine the clinical variables associated with inadequate salvage cryotherapy and to correlate the disease-free survival rates associated with biopsy results in prostate cancer (CaP).

METHODS AND MATERIALS

Between July 1992 and January 1995, 150 patients underwent salvage cryotherapy for locally recurrent CaP. Biopsy specimens were examined for the presence of cancer cells and normal or atypical glands, all of which were considered evidence of inadequate cryotherapy. Clinical variables, as predictors of biopsy results, were evaluated with univariate and multivariate analyses. The impact of the biopsy results on disease-free survival was also determined.

RESULTS

The number of cryoprobes and freeze-thaw cycles correlated with inadequate cryotherapy (p = 0.037 and p = 0.0022, respectively). The number of freeze-thaw cycles was an independent predictor of inadequate cryotherapy (p = 0.003). The finding of cancer cells in the biopsy specimens was the only histopathologic variable that affected disease-free survival (p = 0.016).

CONCLUSION

Complete ablation of the prostate gland and tumor is difficult to achieve with salvage cryotherapy. To optimize for complete ablation, salvage cryotherapy should include at least two freeze-thaw cycles and a minimum of five cryoprobes. The finding of atypical or normal epithelial tissue in biopsy specimens after salvage cryotherapy is not predictive of biochemical failure.

Cryotherapy for prostate cancer

Cryotherapy, or the use of freezing, is a long-established method of tumor cell destruction. Although in the past cryotherapy was widely used as a local treatment for prostate cancer, this technique was abandoned not due to lack of efficacy but because the complication rate was unacceptably high. However, there has been a re-emergence in the popularity of cryotherapy for the treatment of localized prostate cancer due to improvements in instrumentation, tumor localization and treatment delivery. Using transrectal ultrasound imaging, prostate cryotherapy is currently delivered with multiple probes via a percutaneous transperineal approach. The extent of freezing can be precisely controlled and monitored with thermocouples and tissue destruction is monitored with real-time visualization of the prostate and surrounding structures. The role of cryotherapy in localized prostate cancer is reviewed.

Prospective trial of cryosurgical ablation of the prostate: five-year results

OBJECTIVES

To determine in a prospective pilot study the safety and efficacy of cryosurgical ablation for localized prostate carcinoma.

METHODS

A total of 87 cryosurgical procedures were performed on 76 consecutive patients between December 1994 and February 1998. All patients had histologically proved adenocarcinoma of the prostate, with prostate-specific antigen (PSA) readings of less than 30 ng/mL. Clinical evaluations, PSA determinations, and patient self-reported quality-of-life questionnaires (functional assessment of cancer treatment-prostate; FACT-P) were used to determine biochemical and clinical disease-free status and complications. Patients had a mean follow-up of 50 months (minimum 36).

RESULTS

Follow-up biopsies were performed in 73 patients, and 72 were negative for malignancy after one or more treatments. Ten patients required two treatments and 1 patient required three treatments. The 5-year overall and cancer-specific survival rate was 89% (95% confidence interval, 83% to 97%) and 98.6% (95% confidence interval, 96% to 100%), respectively. The undetectable PSA rate (less than 0.3 ng/mL) for low-risk patients (n = 13) was 60% at 5 years; for moderate-risk patients (n = 23), it was 77%, and for high-risk patients (n = 40), 48%. The corresponding percentage of patients with a PSA level less than 1.0 ng/mL at 5 years was 75%, 89%, and 76%. Sloughing occurred in 3 patients (3.9%), incontinence in 1 (1.3%), and testicular abscess in 1 (1.3%). At 3 years, 18 (47%) of 38 patients capable of unassisted intercourse at the time of cryosurgery had resumed sexual intercourse, 5 spontaneously and 13 with sildenafil or prostaglandin.

CONCLUSIONS

The results of this prospective evaluation show cryosurgery to be both a safe and an effective option in the treatment of localized prostate cancer.

Prostate cryoablation: a scientific rationale for future modifications

This investigation was designed to identify potential directions for future modification of the percutaneous prostate cryoablation procedure. An analysis of prostate cancer location and volume in radical prostatectomy specimens was performed to evaluate the potential clinical consequences of these proposed modifications. A list of recommendations for improvements in the prostate cryoablation procedure was compiled from informal discussions held with participants in 9 training courses and conferences on prostate cryoablation over 18 months. Subsequently, a population of 112 consecutive, sagittally sectioned whole-mount radical prostatectomy samples was evaluated for prostate cancer volume, number of individual foci, and location to examine the disease-specific outcomes of these proposed modifications. The most common areas for potential alterations in the current cryoablation technique include modifications that would further simplify the procedure, continue to reduce real and perceived toxicity, and augment efficacy. Importantly, modifications designed to reduce treatment side effects could conflict with efforts designed to improve eradication of prostate cancer. Pathologic analysis revealed multifocal cancer in 79.5% of the samples, with 66% of cases exhibiting cancer within 5 mm of the urethra. The median volume of the index cancer was 1.6 cm3, whereas the median volume of the smaller ancillary lesions was 0.3 cm3. Prostate parenchymal-sparing alterations, proposed to reduce incontinence and erectile dysfunction by targeting the index cancer, would likely eradicate clinically significant cancer in 79% of men. The recent enthusiasm for prostate cryoablation as a reasonable minimally invasive treatment option for men with clinically localized cancer is likely to result in modifications of the established surgical technique. Knowledge of the anatomic location and cancer volume within the prostate gland is an important adjunct to planning such alterations. It is possible that parenchymal-sparing modifications to total gland prostate cryoablation can eradicate clinically significant cancer in most men, with a reduction in toxicity and cost.

The evolution and state of modern technology for prostate cryosurgery

Cryosurgery is the in situ ablation of a target tissue by application of extreme cold temperature. The ability of cryosurgery to ablate tissue is unquestioned. It is the controlled application of a cryoinjury in a manner to minimize morbidity that is problematic. Prostate cryosurgery is complicated by the proximity of the prostate to adjacent structures that are sensitive to a freeze injury, namely the urethra, rectal wall, and neurovascular bundles. Several recent technological advances have led to the development of an effective treatment protocol with acceptable morbidity. These include the advent of real-time transrectal ultrasound, cryomachines with almost instant freeze-thaw control through the use of the Joule-Thompson effect, and warming catheters to effectively preserve the integrity of the urethra and external sphincter. Further, temperature monitoring at the posterior margin of the prostate sometimes combined with an injection of saline solution into Denonvilliers fascia has reduced the occurrence of urethrorectal fistula formation to 0% to 0.5% in modern series. We review the key innovations of prostate cryosurgery that differentiate this state-of-the-art procedure from that used by early investigators to even that of the early 1990s. Potential future innovations, specifically related to image guidance of the procedure, are also addressed.

Targeted cryoablation of the prostate: 7-year outcomes in the primary treatment of prostate cancer

The efficacy and safety of the long-term experience with targeted cryoablation of prostate cancer (TCAP) at a community hospital is retrospectively reviewed. A series of 590 consecutive patients who underwent TCAP as primary therapy with curative intent for localized or locally advanced prostate cancer from March 1993 to September 2001 were identified. Patients were stratified into 3 risk groups according to clinical characteristics. Biochemical disease-free survival (bDFS), post-TCAP biopsy results, and post-TCAP morbidity were calculated and presented. The mean follow-up time for all patients was 5.43 years. The percentages of patients in the low-, medium-, and high-risk groups were 15.9%, 30.3%, and 53.7%, respectively. Using a prostate-specific antigen (PSA)-based definition of biochemical failure of 0.5 ng/mL, results were as follows: (1) the 7-year actuarial bDFS for low-, medium-, and high-risk patients were 61%, 68%, and 61%, respectively; (2) the bDFS probabilities for a PSA cutoff of 1.0 ng/mL for low-, medium-, and high-risk patients were 87%, 79%, and 71%, respectively; and (3) the bDFS probabilities for low-, medium-, and high-risk patients using the American Society for Therapeutic Radiology and Oncology (ASTRO) definition of biochemical failure (3 successive increases of PSA level) were 92%, 89%, and 89%, respectively. The rate of positive biopsy was 13%. After a positive biopsy, 32 patients underwent repeat cryoablation. For those patients who underwent repeat cryoablation, 68%, 72%, and 91% remain bDFS using definitions of 0.5 ng/mL, 1.0 ng/mL, and the ASTRO criteria, respectively, after a mean follow-up time since repeat cryoablation of 63 months. The rates of morbidity were modest, and no serious complications were observed. TCAP was shown to equal or surpass the outcome data of external-beam radiation, 3-dimensional conformal radiation, and brachytherapy. These 7-year outcome data provide compelling validation of TCAP as an efficacious treatment modality for locally confined and locally advanced prostatic carcinoma.

Cryosurgery as primary treatment for localized prostate cancer: a community hospital experience

The technique and recent experience incorporating cryosurgery into our community practice for primary treatment of localized prostate cancer is described. Between December 2000 and December 2001, a total of 93 patients underwent targeted cryoablation for localized prostate cancer. Of the 93 patients, 18 had failed radiotherapy, and cryotherapy was used as salvage therapy. The remaining 75 patients underwent targeted cryoablation of the prostate as primary therapy. A single urologist using an argon-based cryoablation system performed the procedure. Cryoprobes and thermosensors were placed under transrectal ultrasound guidance via a transperineal route. A double freeze-thaw cycle was used with anterior-to- posterior probe operation. Strategically placed thermosensors were used to monitor and control the freezing, and a warming catheter was used to protect the urethra. We achieved a nadir prostate-specific antigen level of < or =0.4 ng/mL in 84% of the entire population we studied (63 of 75 patients). Postsurgery complications were minimal. Incontinence developed in 4 patients, as did postsuprapubic catheter removal urinary retention. Erectile dysfunction developed in 28 of 34 patients who were potent preoperatively, with 6 of the 34 patients regaining potency after surgery. No rectourethral fistula formation occurred. Urethral sloughing was observed in 5 patients, 1 of whom developed a scrotal abscess during treatment of the sloughing. The use of cryoablation of the prostate for the treatment of localized adenocarcinoma of the prostate is feasible and can easily be transferred from the pioneering centers to the community hospitals without sacrificing safety or efficacy.

Image-guided prostate cryosurgery: state of the art

BACKGROUND

Cryosurgery was first used to treat prostate cancer in the early 1970s but it was not until 1993, when the results from percutaneous ultrasound-guided cryosurgery were published, that the potential advantages of this treatment became apparent. Changes in equipment and techniques have improved the results of cryosurgery, in both tumor control and lower morbidity.

METHODS

The author has reviewed data of his own and those of others concerning the changes in techniques employed and outcomes from prostate cryosurgery.

RESULTS

Ultrasound-guided percutaneous transperineal placement of the cryoprobes allows monitoring of freezing in real time. Monitoring temperature at critical locations, separating the rectum and prostate by saline injection, and using argon gas rather than liquid nitrogen-based equipment have improved results and lowered complication rates. The technique produces outcomes similar to those obtained with brachytherapy and three-dimensional conformal radiation therapy.

CONCLUSIONS

Advantages of cryosurgery include the ability to re-treat patients without added morbidity and to treat salvage postradiation patients with acceptable results and morbidity. The recent demonstration that "nerve-sparing" cryosurgery is possible suggests that cryosurgery may be used more often.

Results of salvage cryoablation of the prostate after radiation: identifying predictors of treatment failure and complications

PURPOSE

We conduct a critical evaluation of cryoablation of prostate cancer after failure of full dose radiotherapy to identify predictors of treatment failure and complications.

MATERIALS AND METHODS

A total of 125 cryoablation procedures were performed in 118 patients with proved local recurrence after full dose radiotherapy. Followup includes serial prostate specific antigen (PSA) and biopsy at 6,12 and 24 months. Kaplan-Meier plots were constructed for different PSA cutoffs. We separately analyzed different cohorts based on T stage, Gleason score, PSA before cryoablation and endocrine therapy status.

RESULTS

Of the 118 patients 114 had serum PSA nadir less than 0.5 ng./ml. Median followup was 18.6 months (range 3 to 54). Of the biopsy cores 3.1% (23 of 745) from 7 patients contained persistent viable cancer. Kaplan-Meier plots showed patients free of histological failure leveling at 87% and free from biochemical failure at 68%, 55% and 34%, respectively, with PSA greater than 4, 2 and 0.5 ng./ml. PSA greater than 10 ng./ml. before cryoablation, Gleason score 8 or greater before radiation and stage T3/T4 disease appeared to predict an unfavorable biochemical outcome. Serious complications included 4 rectourethral fistulas (3.3%) and severe incontinence (6.7%). Strong predictors of complications included bulky disease for fistulas and prior transurethral surgery.

CONCLUSIONS

Salvage cryoablation after radiation can achieve reasonable biochemical and histological results with acceptable morbidity. Cryoablation appears to be a reasonable treatment option for this patient population with few viable therapeutic options, provided vigorous patient selection criteria are adhered to.

Chemo-cryo combination therapy: an adjunctive model for the treatment of prostate cancer

Despite continuing research and the development of alternate therapeutic options, prostate cancer remains problematic. Chemotherapy has played a minor role as a treatment option due to its lack of efficacy. Whereas cryotherapy has received renewed attention as a treatment modality, it too fails to offer an absolute curative option. Previously, we reported on the utilization of a therapeutic model, which, in combination, increases cell death in a canine renal cell model. Based upon that study, we investigated a combination therapy model as an alternative for the treatment modality for prostate cancer. We hypothesized that the combination of chemotherapy and cryosurgery would result in enhanced cell death, thereby presenting a more effective treatment of prostate cancer. A human prostate cancer cell (PC-3) model was exposed to 5-fluorouracil (5-FU) for 2 and 4 days (prefreeze), freezing (-5 to -100 degrees C), or a combination of the two treatments, and each was assessed for effectiveness over a 2-week posttreatment period. Additionally, investigation into the mechanisms of cell death initiated by the respective therapies was performed through DNA cleavage analysis. For chemotherapy, cultures exposed to 5-FU (2-4 days) yielded a 15-25% loss in cell survival. For cryotherapy, cultures exposed to a temperature window of -5 to -20 degrees C yielded an initial 5-70% loss of viability but cells propagated over time. Cultures exposed to temperatures of -25 to -80 degrees C yielded a 90-99% (+/-4.5%) initial loss in viability with repopulation observed by 12 days postthaw. Cells frozen to -100 degrees C yielded 100% (+/-0.3%) loss of viability and exhibited no signs of propagation. For chemo-cryo therapy, combination treatment at milder temperatures (-5 to -25 degrees C) resulted in an enhanced loss of cell viability compared to that for either treatment alone. Combination treatment at lower temperatures (-40 to -80 degrees C) resulted in a complete loss of cell viability. DNA fragmentation analysis at 48 h posttreatment revealed that dead (detached) cells treated with 5-FU died primarily through apoptosis, whereas dead cells from freezing (-15 degrees C) alone died primarily through freeze-rupture and necrosis. Detached cell analysis from combination treatment at -15 degrees C revealed the presence of apoptotic, necrotic, and freeze-rupture cell death. Scanning electron micrographs of cells exposed to freezing contributing to cell death. These data demonstrate that the combination of 5-FU at sublethal doses and freezing temperatures improves human prostate cancer cell death efficacy. Further, we suggest that chemo-cryo therapy offers a potential alternative treatment for the control and eradication of prostate cancer.

Five-year retrospective, multi-institutional pooled analysis of cancer-related outcomes after cryosurgical ablation of the prostate

OBJECTIVES

To define the potential role of cryosurgical ablation of the prostate (CSAP) as a treatment option for patients with localized prostate carcinoma (PCA), we performed a retrospective outcomes analysis of a large database of patients undergoing CSAP constructed from five institutions and compared this with matching outcomes from contemporary reports of patient outcomes after radiotherapy.

METHODS

A total of 975 patients who underwent CSAP as primary therapy from January 1993 to January 1998 with sufficient outcomes data available were identified. Patients were stratified into three groups on the basis of their clinical features. Biochemical-free survival (BFS), post-CSAP biopsy results, and post-CSAP morbidities were calculated and recorded.

RESULTS

The median follow-up for all patients was 24 months. The percentages of patients in the low, medium, and high-risk groups were 25%, 34%, and 41%, respectively. For prostate-specific antigen thresholds of less than 0.5 and less than 1.0 ng/mL, the 5-year actuarial BFS ranged from 36% to 61% and 45% to 76%, respectively, depending on the risk category. Overall, the positive biopsy rate was 18%. Morbidities included impotence in 93%, incontinence in 7.5%, rectourethral fistula in 0.5%, and transurethral resection of the prostate in 13% of patients (10% approved warming catheters versus 40% nonapproved).

CONCLUSIONS

For each risk group, the 5-year BFS and positive biopsy rate after CSAP was comparable to matching outcomes reported after radiotherapy. Morbidities also seemed comparable, with impotence rates higher and rectal injury rates lower after CSAP than after radiotherapy. These data indicate that CSAP can be performed with low morbidity and can produce cancer-related results comparable to those reported for patients undergoing radiotherapy.