Percutaneous transperineal prostate cryosurgery using transrectal ultrasound guidance: animal model

Defeating Cancers' Adaptive Defensive Strategies Using Thermal Therapies: Examining Cancer's Therapeutic Resistance, Ablative, and Computational Modeling Strategies as a means for Improving Therapeutic Outcome

BACKGROUND

Diverse thermal ablative therapies are currently in use for the treatment of cancer. Commonly applied with the intent to cure, these ablative therapies are providing promising success rates similar to and often exceeding "gold standard" approaches. Cancer-curing prospects may be enhanced by deeper understanding of thermal effects on cancer cells and the hosting tissue, including the molecular mechanisms of cancer cell mutations, which enable resistance to therapy. Furthermore, thermal ablative therapies may benefit from recent developments in computer hardware and computation tools for planning, monitoring, visualization, and education.

METHODS

Recent discoveries in cancer cell resistance to destruction by apoptosis, autophagy, and necrosis are now providing an understanding of the strategies used by cancer cells to avoid destruction by immunologic surveillance. Further, these discoveries are now providing insight into the success of the diverse types of ablative therapies utilized in the clinical arena today and into how they directly and indirectly overcome many of the cancers' defensive strategies. Additionally, the manner in which minimally invasive thermal therapy is enabled by imaging, which facilitates anatomical features reconstruction, insertion guidance of thermal probes, and strategic placement of thermal sensors, plays a critical role in the delivery of effective ablative treatment.

RESULTS

The thermal techniques discussed include radiofrequency, microwave, high-intensity focused ultrasound, laser, and cryosurgery. Also discussed is the development of thermal adjunctive therapies-the combination of drug and thermal treatments-which provide new and more effective combinatorial physical and molecular-based approaches for treating various cancers. Finally, advanced computational and planning tools are also discussed.

CONCLUSION

This review lays out the various molecular adaptive mechanisms-the hallmarks of cancer-responsible for therapeutic resistance, on one hand, and how various ablative therapies, including both heating- and freezing-based strategies, overcome many of cancer's defenses, on the other hand, thereby enhancing the potential for curative approaches for various cancers.

Assessment of Cryosurgical Device Performance Using a 3D Tissue-Engineered Cancer Model

As the clinical use of cryoablation for the treatment of cancer has increased, so too has the need for knowledge on the dynamic environment within the frozen mass created by a cryoprobe. While a number of factors exist, an understanding of the iceball size, critical isotherm distribution/penetration, and the resultant lethal zone created by a cryoprobe are critical for clinical application. To this end, cryoprobe performance is typically characterized based on the iceball size and temperature penetration in phantom gel models. Although informative, these models do not provide information as to the impact of heat input from surrounding tissue nor give any information on the ablative zone created. As such, we evaluated the use of a tissue-engineered tumor model (TEM) to assess cryoprobe performance including iceball size, real-time thermal profile distribution, and resultant ablative zone. Studies were conducted using an Endocare V-probe cryoprobe, with a 10/5/10 double freeze–thaw protocol using prostate and renal cancer TEMs. The data demonstrate the generation of a 33- to 38-cm3 frozen mass with the V-Probe cryoprobe following the double freeze of which ∼12.7 and 6.5 cm3 was at or below −20°C and −40°C, respectively. Analysis of ablation zone using fluorescence microscopy 24 hours postthaw demonstrated that the internal ∼40% of the frozen mass was completely ablated, whereas in the periphery of the iceball (outer 1 cm region), a gradient of partial to minimal destruction was observed. These findings correlated well with clinical reports on renal and prostate cancer cryoablation. Overall, this study demonstrates that TEMs provide an effective model for a more complete characterization of cryoablation device performance. The data demonstrate that while the overall iceball size generated in the TEM was consistent with published reports from phantom models, the integration of an external heat load, circulation, and cellular components more closely reflect an in vivo setting and the impact of penetration of the critical (−20°C and −40°C) isotherms into the tissue. This is important as it is well appreciated in clinical practice that the heat load of a tissue, cryoprobe proximity to vasculature, and so on, can impact outcome. The TEM model provides a means of characterizing the impact on ablative dose delivery allowing for a better understanding of probe performance and potential impact on ablative outcome.

Re-purposing cryoablation: a combinatorial 'therapy' for the destruction of tissue

It is now recognized that the tumor microenvironment creates a protective neo-tissue that isolates the tumor from the various defense strategies of the body. Evidence demonstrates that, with successive therapeutic attempts, cancer cells acquire resistance to individual treatment modalities. For example, exposure to cytotoxic drugs results in the survival of approximately 20-30% of the cancer cells as only dividing cells succumb to each toxic exposure. With follow-up treatments, each additional dose results in tumor-associated fibroblasts secreting surface-protective proteins, which enhance cancer cell resistance. Similar outcomes are reported following radiotherapy. These defensive strategies are indicative of evolved capabilities of cancer to assure successful tumor growth through well-established anti-tumor-protective adaptations. As such, successful cancer management requires the activation of multiple cellular 'kill switches' to prevent initiation of diverse protective adaptations. Thermal therapies are unique treatment modalities typically applied as monotherapies (without repetition) thereby denying cancer cells the opportunity to express defensive mutations. Further, the destructive mechanisms of action involved with cryoablation (CA) include both physical and molecular insults resulting in the disruption of multiple defensive strategies that are not cell cycle dependent and adds a damaging structural (physical) element. This review discusses the application and clinical outcomes of CA with an emphasis on the mechanisms of cell death induced by structural, metabolic, vascular and immune processes. The induction of diverse cell death cascades, resulting in the activation of apoptosis and necrosis, allows CA to be characterized as a combinatorial treatment modality. Our understanding of these mechanisms now supports adjunctive therapies that can augment cell death pathways.

Histological outcomes after focal high-intensity focused ultrasound and cryotherapy

Introduction

Focal therapy has increasingly become an accepted treatment option for patients with localised prostate cancer. Most follow-up protocols use a mixture of protocol biopsies or “for cause” biopsies triggered by a rising PSA. In this paper, we discuss the histological outcomes from these biopsies and their use in guiding subsequent management and trial development.

Methods

We conducted a literature search and reviewed the post-treatment biopsy results from studies on focal HIFU and focal cryotherapy. We subsequently reviewed the results of three recently published consensus statements released discussing many of the issues concerning focal therapy.

Results

Research suggests that 1 in 5 of all post-treatment biopsies after focal therapy are positive. However, the majority of these seemed to be from the untreated portion of the gland or met criteria for clinically insignificant disease. The histological outcomes from focal therapy are promising and confirm its effectiveness in the short to medium term. Furthermore re-treatment is possible whilst maintaining a low-side-effect profile.

Conclusion

Debate is ongoing about the clinical significance of various levels of residual disease after focal therapy and the exact threshold at which to call failure within a patient who has had focal therapy.

Cryotherapy for primary treatment of prostate cancer: intermediate term results of a prospective study from a single institution

Purpose. Published data about cryotherapy for prostate cancer (PC) treatment are based on case series with a lack of clinical trials and the inexistence of a validated definition of biochemical failure. A prospective study with standardized followup protocol was conducted in our institution. Material and Methods. Prospective study of a series of cases including 108 patients diagnosed with localized PC at clinical stage T1c-T2c treated by primary cryoablation and median followup of 61 months. Criteria of biochemical recurrence were unified according to the American Society for Therapeutic Radiology and Oncology (ASTRO). End points were biochemical progression-free survival (BPFS), cancer-specific survival, and overall survival. Rate of complications was reported. Results. The BPFS for low-, medium-, and high-risk patients was 96.4%, 91.2%, and 62.2%, respectively. Cancer-specific survival was 98.1%. Overall survival reached 94.4%. Complications included incontinence in 5.6%, urinary tract obstruction in 1.9%, urethral sloughing in 5.6%, haematuria in 1.9%, perineal pain in 11.1%, and prostatorectal fistula in 0.9%. Erectile disfunction was found in 98.1%. Conclusions. Cryotherapy is an effective and minimally invasive treatment for primary PC in well-selected cases, with low surgical risk and good results in terms of BPFS, cancer-specific survival, and overall survival.

Ultrasound signal wavelet analysis to quantify the microstructures of normal and frozen tissues in vitro

Cryosurgery has a number of advantages that make it particularly appealing in the treatment of liver cancer. However, a major problem for the wide clinical adoption of hepatic cryosurgery is the lack of a cost effective high resolution imaging way which is capable of both performing precise monitoring of the freezing process in situ and evaluating the postoperative effects after surgery. The mean scatterer spacing has been found to be an important parameter for describing the ultrasonic scattering and characterization of biological tissues. However, its potential values in the evaluation of cryosurgical effects of tissues reserved unclear so far. Here, we investigated the wavelet analysis to estimate the mean scatterer spacing parameter in normal and freeze-thawed tissues on porcine livers in vitro. The experimental results carried out at 10 MHz using weakly focused pulse-echo signal element transducer indicated that the mean scatterer spacing in normal liver tissues is 1.12 ± 0.13 mm whereas it is 1.67 ± 0.25 mm in several pre-frozen and then thawed tissues. These results disclosed the good correlation between the wavelet data and microstructures of the normal or thawed tissues, and hence demonstrated that the wavelet analysis holds promise to be used as an effective method for the characterization of thawed tissues scatterer spacing. The present method offers a potential pragmatic strategy for monitoring the transition zone between frozen and unfrozen tissues during the surgical therapy, and evaluating postoperative effects.

Bilateral focal ablation of prostate tissue using low-energy direct current (LEDC): a preclinical canine study

OBJECTIVE

To evaluate side-effects, erectile function and capability to preserve adjacent tissues of bilateral focal prostate ablation using low-energy direct current (LEDC) in a canine model.

MATERIALS AND METHODS

In all, 12 male Beagle dogs underwent bilateral focal prostate ablation using the NanoKnife™ LEDC system. Three 19 G monopolar electrodes were transperineally placed on each side of the prostate under transrectal ultrasonographic (TRUS) guidance using a triangular probe array. Intra- and postoperative side-effects were recorded. Erectile function was evaluated at baseline and 4-5 and 26-27 days after ablation. The dogs were killed humanely at 7 (six) and 30 days (six) for gross and microscopic evaluation of the prostate and adjacent organs.

RESULTS

The median (range) prostate volume on TRUS was 12.1 (8.9-17.2) mL. The electrodes were placed at a median distance of 0.55-0.66 cm from the capsule, urethra and rectum. All procedures were completed successfully and recovery was uneventful. There were no episodes of urinary retention. All the dogs were able to achieve erections after ablation. Pathological analyses revealed inflammatory changes in the ablation zone at 7 days and replacement by fibrosis at 30 days. On microscopic examination no histological injury to the capsule, urethra, rectal wall or nervous structures was identified.

CONCLUSIONS

In this study, bilateral focal prostate ablation using LEDC was safe and had a favourable side-effects profile limited to transient minor events. LEDC ablation effectively spared adjacent structures as well as physiological functions in all the dogs.

Contemporary technique of intraoperative 3-dimensional ultrasonography-guided transperineal prostate cryotherapy

Successful cryotherapy of the prostate for neoplasms relies on imaging to achieve good oncological outcomes with minimal complications. Traditional prostatic cryotherapy relies on 2-dimensional ultrasonography (2DUS) guidance, which often makes it difficult to track the passage of needles in an oblique plane. We describe our initial 3-dimensional ultrasonography (3DUS) system, and the subsequent improvements that have been made during the last 10 years. Our imaging system uses a Philips HDI 5000 ultrasonography unit, a standard PC, a Matrox Meteor II video frame grabber and 3DUS developed at Robarts Research Institute. For the cryotherapy we use ultrathin (17-gauge) IceRod needles. After image acquisition, preplanning is performed using the 3-dimensional (3D) software, and then the IceRod needles are inserted into the prostate. As the freezing process commences, continuous 3DUS images are taken and analyzed during the double freeze-thaw cycles to monitor the progress of the ice ball formation. Real-time intraoperative 3D imaging of the prostate during cryotherapy has allowed us to accurately preplan and then monitor the progression of ice ball formation, which represents a significant advantage over conventional 2DUS.

Cryoimmunotherapy in urologic oncology

Cryoablation is gaining acceptance as a primary treatment of localized as well as a salvage therapy of metastatic urologic malignancies. Anecdotal clinical reports suggest cryoablation can induce a systemic anti-tumor immune response; this phenomenon has been confirmed in animal models. To capitalize on this stimulatory effect of cryotherapy for control of advanced malignancies, it must be further intensified. This article reviews the existing evidence regarding cryoimmunology and discusses the mechanisms for generation of an anti-tumor immune response. Several immunotherapy approaches that can be combined with cryoablation to devise a cryoimmunotherapeutic strategy with potential to affect the progression of metastatic disease are described.

Ten-year biochemical disease control for patients with prostate cancer treated with cryosurgery as primary therapy

OBJECTIVES

Prostate cryosurgery has been increasingly used for the management of localized prostate cancer since its introduction in a minimally invasive form in the early 1990s. We performed a retrospective study of the largest and most mature patient group treated with cryosurgery reported thus far.

METHODS

We retrospectively analyzed the data from 370 patients treated consecutively from 1991 to 1996 with a focus on the determination of biochemical disease-free survival for a group of patients with T1 to T3 prostate cancer who had undergone prostate cryosurgery as primary monotherapy. Only patients with no previous radiotherapy, hormonal therapy, or surgery were included.

RESULTS

The median follow-up was 12.55 years. Using a nadir plus 2 ng/dL definition, Kaplan-Meier analysis demonstrated a biochemical disease-free survival rate at 10 years of 80.56%, 74.16%, and 45.54% for low, moderate, and high-risk groups, respectively. The 10-year negative biopsy rate was 76.96%.

CONCLUSIONS

The results for this pilot group of patients who underwent percutaneous prostate cryosurgery monotherapy demonstrated biochemical disease-free survival rates that overlap with those of similar groups of patients treated under similar circumstances using other types of nonextirpative monotherapy.

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.

In vivo MR thermometry of frozen tissue using R2* and signal intensity

Cryoablation is one of several minimally invasive treatments that may be suitable for a targeted treatment of prostate cancer. Because efficacy is improved when a sufficiently cold end temperature is reached, the purpose of this work was to demonstrate an image-based thermometry method that could provide temperature maps throughout the frozen tissue. In five in vivo canine prostate cryoablation experiments performed under magnetic resonance imaging guidance, two MR parameters were measured and correlated to temperature: R2* and changes in signal intensity. R2* is elevated approximately linearly as tissue temperature decreases below the freezing point, while the signal intensity decreases exponentially. In vivo temperature maps with isotherms at -5 degrees C, -15 degrees C, and -30 degrees C are demonstrated.

Role of transrectal ultrasound guided salvage cryosurgery for recurrent prostate carcinoma after radiotherapy

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>or=0.3 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>or=1.0, the values at 1 and 2 y were 72 and 58%.

Laparoscopic cryomyolysis: An alternative to myomectomy in women with symptomatic fibroids

BACKGROUND

The purpose of this study was to determine whether cryomyolysis may present an alternative valid surgical procedure to hysterectomy or myomectomy for selected women with symptomatic fibroids who wish to preserve their uterus but do not desire future pregnancies.

METHODS

Sixty-three women with symptomatic fibroids who refused either myomectomy or hysterectomy, requesting a conservative surgery for myomata, underwent laparoscopic cryomyolysis using a 3- to 5-mm or 8-mm cryoprobe (CRYOcare system).

RESULTS

Our study showed a mean (+/-standard deviation) decrease of myoma volume of 60.3% (+/-20.7) and complete symptom relief in 83.6% (p < 0.001) of patients after a 12-month follow-up from cryomyolysis. No significant intra- or postoperative complications were noted.

CONCLUSION

Cryomyolysis is an effective laparoscopic procedure for obtaining myoma shrinkage and symptom relief in women with symptomatic fibroids who desire to preserve their uterus.

Cryoablation of Renal and Prostate Tumors

During the past decade, cryoablation has been applied to benign and malignant conditions within the prostate and kidney. The essence of cryosurgery lies in producing temperatures low enough to cause necrosis in target tissues while avoiding lethal conditions in healthy peripheral tissues. It works by two main mechanisms: (1) at the cellular level via solute damage and intracellular ice formation; and (2) at the vascular level as a result of thrombosis and subsequent coagulative and ischemic necrosis. Investigation of cryoablation for renal tumors began in 1964, and by the 1990s, attention was turning to its use as a means of treating renal tumors. Modern renal cryosurgery is applied using minimally invasive techniques. Cryotherapy was first applied in the prostate in 1966 and soon thereafter was used to treat prostate cancer. Today, prostate cryosurgical techniques employ ultrasound monitoring and urethral warming to minimize urethral and rectal complications.

Cryothermic and hyperthermic treatments of human leiomyomata and adjacent myometrium and their implications for laparoscopic surgery

STUDY OBJECTIVE

To evaluate the effects and feasibility of direct cryothermic and hyperthermic therapy on leiomyomata and adjacent myometrium, and to contribute to evidence-based treatment thresholds based on measurements of direct cell injury.

DESIGN

Experimental study (Canadian Task Force classification II-2).

SETTING

University hospital.

SUBJECTS

Leiomyoma and myometrium tissue from 10 women undergoing total abdominal hysterectomy with or without bilateral salpingo-oophorectomy.

INTERVENTION

In vitro cryothermic or hyperthermic therapy was performed with representative leiomyoma and myometrium tissue samples. Using a directional solidification stage to simulate cryothermic therapy, 10 leiomyoma and 6 myometrium specimens were cooled in vitro at a rate of -5 degrees C/minute to end temperatures of -20 degrees, -40 degrees, -60 degrees, and -80 degrees C with a 15-minute hold period and then rapidly thawed to 21 degrees C. Hyperthermic therapy was simulated using a preheated 45 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, and 80 degrees C constant temperature copper heating block with a 10-minute treatment period. In conjunction with tissue culturing and control tissues, cell death was assessed with routine histology and viability dyes (ethidium homodimer/Hoechst).

MEASUREMENTS AND MAIN RESULTS

In cryothermic results, leiomyomata cell death (LCD) increased from 12% to 27% by histology and 26% to 38% by viability dye assay over the thermal range from -20 degrees to -80 degrees C, respectively. Myometrial cell death (MCD) increased from 10% to 12% and 4% to 20% for the same measurements, respectively. Whereas MCD appeared relatively stable from -40 degrees to -80 degrees C, it was significantly less than LCD over this range (p <0.05). For hyperthermic results, LCD increased from 17% to 88% by histology with progressive temperature increase from 45 degrees to 80 degrees C, respectively. The MCD showed a similar increase from 16% to 91% by histology over this temperature range. Hyperthermic histology and dye assay results were similar for LCD and MCD.

CONCLUSIONS

In comparison with myometrium, leiomyomata showed greater direct cryothermic and equal hyperthermic cell injury. Whereas cell death increased up to 70 degrees C and down to -80 degrees C, the interval increases in cell injury diminished with more extreme temperatures. In vivo studies of combined direct and ischemic vascular injury thresholds have yet to be performed, but direct LCD matrixes determined in this study will help provide guidelines for minimally invasive surgical techniques for the treatment of leiomyomata.

Salvage external beam radiotherapy for clinical failure after cryosurgery for prostate cancer

PURPOSE

To investigate the role of external beam radiotherapy (EBRT) as salvage treatment of prostate cancer after cryosurgery failure.

METHODS AND MATERIALS

Between 1993 and 1998, 6 patients underwent EBRT with curative intent for local recurrence of prostate cancer after cryosurgery. All 6 patients had biopsy-proven recurrence and palpable disease on digital rectal examination at the time of EBRT. The median follow-up was 34 months (range 8-46). The median prostate-specific antigen level was 2.3 ng/mL (range 0.8-4.1). No patient had evidence of metastatic disease. Two patients received hormonal therapy before beginning EBRT. No patient received hormonal therapy after EBRT completion. The median elapsed time between cryosurgery and EBRT was 3 years (range 1.5-4). The median delivered dose was 66 Gy (range 62-70.2) using a 10-MeV photon beam. An in-house-developed three-dimensional treatment planning system was used to plan delivery of the prescribed dose with conformal radiotherapy techniques.

RESULTS

After EBRT, all patients had complete resolution of palpable disease. Four patients (66%) were disease free at the time of the last follow-up. Two patients developed biochemical failure as defined by the American Society for Therapeutic Radiology and Oncology consensus definition. One of these patients had a prostate-specific antigen level of 97 ng/mL before cryosurgery. No patient developed distant metastasis during follow-up. Two patients (33%) developed proctitis; 1 case resolved with Rowasa suppositories and 1 required blood transfusion.

CONCLUSIONS

Our preliminary results suggest that EBRT can render a significant number of patients biochemically free of disease and can cause complete resolution of clinically palpable disease after initial cryosurgery. The results also showed that EBRT can be given without excessive morbidity. EBRT should be considered as a treatment option in these potentially curable cases.

Patient-reported complications after cryoablation therapy for prostate cancer

OBJECTIVES

To define the patient-reported complications after cryoablation therapy for prostate cancer and to compare these results to previously published patient-reported complications for radical prostatectomy and external beam irradiation.

METHODS

A questionnaire similar to previously published patient-reported complication studies was sent to the first 290 patients treated by cryoablation therapy at our institution. The questionnaire was returned by 267 patients. Forty-four patients were excluded from analysis because of prior irradiation, transurethral prostatectomy, or cryoablation, resulting in a study group of 223 patients.

RESULTS

Of the 208 patients with good urinary control preoperatively, 9 (4.3%) patients used incontinence pads after cryoablation. Seven of the 8 patients who used one pad daily reported leakage of only a few drops. Impotency, defined as an inability to obtain erections adequate for vaginal penetration, occurred in 85% of men who were potent preoperatively. Urethrorectal fistula occurred in 1 patient (0.4%). Bladder outlet obstruction caused by stricture or sloughed necrotic prostatic tissue required dilation or transurethral resection in 10% of patients. Scrotal swelling, penile tingling, and pelvic pain occurred in 18%, 15%, and 12% of patients, respectively; typically, these resolved spontaneously within 3 months.

CONCLUSIONS

Patient-reported complications for cryoablation compared favorably to those reported for radical prostatectomy and external beam irradiation. Patient satisfaction was high; 96% of patients reported that they would choose cryosurgery as a treatment option again.

Determination of optimal freezing parameters of human prostate cancer in a nude mouse model

BACKGROUND

We sought to determine whether more than one freeze/thaw cycle is required and what minimum temperature reliably kills prostate cancer in vivo.

METHODS

Two human prostate cancer cell lines (LNCaP and PC3) were implanted subcutaneously in male nude BALB/c mice. Tumors were frozen with contemporary cryosurgery equipment and monitored for temperature, size, and serum prostate-specific antigen (PSA) measurements. The tumors were subjected to one or two freeze/thaw cycles through a wide range of temperatures from 0 - -80 degrees C.

RESULTS

These experiments show that a single freeze/thaw to a temperature < -40 degrees C is adequate to kill most tumor cells in this mouse model of prostate cancer.

CONCLUSIONS

Freezing prostate cancer to < -40 degrees C and ensuring that the entire tumor is frozen is more important than additional freeze/thaw cycles in this experimental model.

A model for the time-dependent thermal distribution within an iceball surrounding a cryoprobe

The optimal cooling parameters to maximize cell necrosis in different types of tissue have yet to be determined. However, a critical isotherm is commonly adopted by cryosurgeons as a boundary of lethality for tissue. Locating this isotherm within an iceball is problematic due to the limitations of MRI, ultrasound and CT imaging modalities. This paper describes a time-dependent two-dimensional axisymmetric model of iceball formation about a single cryoprobe and extensively compares it with experimental data. Thermal histories for several points around a CRYOprobe are predicted to high accuracy (5 degrees C maximum discrepancy). A realistic three-dimensional probe geometry is specified and cryoprobe temperature may be arbitrarily set as a function of time in the model. Three-dimensional temperature distributions within the iceball, predicted by the model at different times, are presented. Isotherm locations, as calculated with the infinite cylinder approximation, are compared with those of the model in the most appropriate region of the iceball. Infinite cylinder approximations are shown to be inaccurate when applied to this commercial probe. Adopting the infinite cylinder approximation to locate the critical isotherm is shown to lead the user to an overestimate of the volume of target tissue enclosed by this isotherm which may lead to incomplete tumour ablation.

In vivo results with a new device for ultrasonic monitoring of pig skin cryosurgery: the echographic cryoprobe

One of the main difficulties encountered in cryosurgery is the uncertainty in the extent and depth of the tissue effectively treated during the freezing process. The objective of this study was to evaluate in vivo ultrasonic control of skin cryosurgery using a new echographic cryoprobe. An echographic cryoprobe, developed specifically for dermatology applications, combines a high-frequency (20 MHz) miniature ultrasonic transducer and a N2O-driven closed cryoprobe. Knowledge of the ultrasound velocity of frozen skin is a prerequisite for monitoring the iceball formation kinetics. Therefore, in a first study, we estimated the ultrasound velocity of frozen skin specimens. In a second step, the operation of the echographic cryoprobe was assessed, under in vivo conditions similar to those used in human therapeutics, on normal skin of three female "Large-White" pigs under anesthesia. The mean value of ultrasound velocity of frozen skin obtained by pooling the data from all the skin specimens included in this study was 2865 +/- 170 m per s. The average rates of growth (10(-2) mm per s) of the iceballs were found to be 12.2 +/- 1.0 (pig 1), 9.0 +/- 1.0 (pig 2), and 8.4 +/- 0.9 (pig 3). The echographic cryoprobe had a built-in high-frequency ultrasonic transducer that served two functions. It enabled in vivo real-time monitoring of depth penetration of the iceball and it gave important feedback to the operator or to the console relating to the rate of growth of the iceball. Automatic (i.e., operator-independent) detection of the echo signal from the freezing front and calculation of the depth penetration of the iceball was possible.

Cryoablation for carcinoma of the prostate

Percutaneous transperineal cryoablation of the prostate is now available in the armamentarium for treatment of prostate cancer. Technical advances in real-time transrectal imaging of the prostate and improvements in cryosurgical equipment have brought this modality into the limelight of available prostate cancer management. Cryosurgery can be offered to many patients with prostate cancer. However, the main indications for its use include primary treatment for localized disease, salvage therapy after failure of traditional methods, and relief of local symptoms. A historical background, description of the technique, and clinical experience at several medical centers including the University of California San Diego, Allegheny General Hospital, University of Texas M.D. Anderson Cancer Center, and Crittenton Hospital, are presented.

Treatment options for localized recurrence of prostate cancer following radiation therapy

Patients with radioresistant clinically localized prostate cancer may be treated by various means. Although androgen ablation is relatively noninvasive, it cannot be considered a curative option. We believe that a subset of patients with locally recurrent prostate cancer without subclinical metastatic disease exists and would benefit from maximally aggressive local therapy. Salvage surgery may offer long-term cancer control, particularly when the tumor is organ-confined, but is a technically challenging operation with a high incidence of postoperative incontinence. Cryoablation of the prostate for postirradiation recurrence may offer a less invasive alternative to radical surgery, but its long-term efficacy remains to be fully determined. Each therapeutic option has its characteristic attendant morbidity and the choice of therapy for local recurrence should be made with informed consent after frank discussion between physician and patient. We propose the treatment algorithm shown in Figure 1 for the management of patients with suspected recurrence after radiation therapy with the caveat that individual therapeutic strategies must be patterned around individual patient needs.

Total incontinence secondary to sphincter destruction after prostate cryotherapy for recurrent prostatic carcinoma

We report a case of total urinary incontinence secondary to sphincter destruction after prostate cryotherapy for recurrent prostatic carcinoma in a 64-year-old man. Periurethral collagen injection was impossible due to inadequate penetration of the injection needle, because of severe scarring and fibrotic changes of the urethra after cryotherapy.

Is there a role for cryoablation of the prostate in the management of localized prostate carcinoma?

It is impossible to adequately answer the question of whether there is a role for CSAP in the management of localized prostate carcinoma without considering the relative advantages and limitations of using other therapies to manage this disease (radical prostatectomy, radiation therapy, hormonal therapy, brachytherapy, expectant observation, and so on). Obviously, this is beyond the scope of this article. It is probably fair to point out, however, that the management of localized prostate carcinoma in the United States is generally quite controversial at the present time, and that despite a considerable amount of data pertaining to these therapeutic alternatives, it is difficult to discern a standard approach that can be broadly applied for all men with this disease. Therefore, if an absence of consensus on the management of localized prostate carcinoma does exist, it seems evident that investigations into alternative therapies are justified, and the preliminary results and efforts investigating CSAP fall well into this paradigm. In this context, several points can be made based on the available information. Significant numbers of patients who undergo CSAP can sustain undetectable levels of PSA for durable periods of time (more than 24 months). Thus, on a clinical level it seems possible to ablate the entire prostate with percutaneous CSAP, although rates of achieving this may be lower than originally anticipated. The reasons for persistence of carcinoma post CSAP are likely technical and related to the difficulties in determining the effective probe placements, number of probes to be used, number of freeze-thaw-freeze cycles to be used, and so on. Previous radiation exposure appears to confer an increased risk of CSAP-related morbidity, with incontinence, tissue sloughing, and rectal injury most prominent. Among nonradiated patients, incontinence is rare, and the most prominent postoperative concern involves BOO/tissue sloughing in a minority of patients. The longest follow-up data available on CSAP suggests that for patients with nonmetastatic prostate carcinoma, CSAP is associated with persistence of carcinoma in only 25% of patients. This compares favorably with the available biopsy data following external beam radiotherapy, in which most reports document positive biopsy results ranging between 30% and 100%, with the majority in the 40% to 50% range. Notably, the positive biopsy rate among patients with stage T3 disease following CSAP at 2 years can be less than 30%, which compares very favorably with previously reported positive biopsy result for these patients following external beam radiation therapy, which ranged between 40% and 100%. The management of patients with persistent carcinoma following CSAP poses fewer concerns to physicians than for those with persistent carcinoma following radiation therapy. Given the number of patients with prostate carcinoma who currently undergo radiotherapy as primary management, these data indicate that CSAP can now be considered a very viable therapeutic alternative for selected patients. With standardizations of technique as well as improved modifications in equipment, these preliminary CSAP results may well improve steadily in the near future. In the absence of randomized, comparative trials, it is difficult to draw meaningful comparisons between CSAP and radical prostatectomy. Based on available information, CSAP appears to be associated with a much lower incidence of stress and total incontinence than is radical prostatectomy. The rates of impotence following CSAP are somewhat comparable to those seen after radical prostatectomy, with wide variation among individual series. For patients who would be ideal candidates for radical prostatectomy (for example, less than stage T2c disease, PSA less than 10 ng/mL, and Gleason score of 7 or less), several authors have noted that the positive biopsy rate between 6 and 12 months is less than 10%.

Cryosurgery of the prostate: techniques and pitfalls

The preliminary data on prostate cryosurgery encompass reports only on local recurrence rates. The procedure is too new to report any survival figures. For localized organ-confined disease, the initial reports at 1 year of positive biopsies following cryosurgery range from 8% to 33%. With clinical stage C disease, a review of the literature also shows a range of 16% to 33% for local recurrence at one year. The largest series of patients treated after failure from radiation therapy is from the M.D. Anderson Cancer Center, which reports a positive biopsy rate of 29% at 6 months. Reports of major complications have included a 2% to 5% incidence of rectourethral fistulas, a 7% to 15% incidence of urinary retention requiring a secondary TURP or prolonged catheter drainage, 2% to 7% incidence of stress incontinence, and a 50% to 80% incidence of impotence. While these overall results may not be optimal to many, they do give us optimism. It is important to recognize that knowledge of the cryosurgical technique is evolving rapidly, and present modifications are not reflected yet in our results. Because hypothermia is a modality proven to cause lethal injury to cancer cells, it would be unfortunate if clinicians dismissed this modality without rigorous review of the surgical technique. The detailed methodology described in this article expedites the learning curve of practicing cryosurgeons and helps to standardize the way cryosurgery is performed.

MR image-guided control of cryosurgery

Cryoablation has recently become a useful procedure for the treatment of prostatic and hepatic tumors, primarily because of advances in the ability to monitor visually the freezing process with ultrasound. Success of the procedure depends in large part on how well the ice front can be positioned to destroy pathologic tissue, while sparing healthy tissue. This study describes a cryogen delivery system that can be used in conjunction with magnetic resonance (MR) image-guided cryoablation, and an automatic control system that uses MR image guidance in a feedback loop to control the ice front trajectory. Edge-detected MR images are used to determine the current ice front location at each time interval, providing feed-back to an automatic control system that adjusts the flow of cryogen to the cryoprobe. Numerical simulations and experimental results demonstrate that an ice front with cylindrical symmetry can be accurately controlled using this MR image-guided feedback control scheme.

La crioablazione della prostata per adenocarcinoma

Physiopathological bases of cryosurgical damage are described: hypothermia, freezing, thawing are all disruptive moments causing necrosis. Last-generation cryosurgical apparatus allows the use of liquid nitrogen circulating through thin probes that are inserted percutaneously under u.s. guidance. Also thermosensors are used to monitor the procedure placing them in selected spots. 404 patients were treated in 3 different but homogeneous groups. Results of control biopsies were available at 3 months for 298 (15 pos.) and for 141 at 12 months (13 pos.). Cryoablation appears to be an interesting procedure, but its complexity requires accurate training with a steep “learning curve”; only long-term follow-up will test in the future its real efficacy.

Transrectal ultrasound-guided transperineal cryoablation in the treatment of prostate carcinoma: preliminary results

PURPOSE

We studied ultrasound-guided percutaneous cryoablation for treatment of prostate carcinoma.

MATERIALS AND METHODS

Our series includes 83 individuals who underwent transrectal ultrasound-guided transperineal percutaneous cryoablation of the prostate. Prostate specific antigen levels, biopsy results and complications were assessed at 3 months.

RESULTS

Of 61 biopsies 8 (13.1%) were positive for carcinoma (half showed stage D disease). Of patients with stages T1 to T3 cancer 92.6% were free of disease at 3 months. Prostate specific antigen levels were significantly decreased by an average of 1.90 ng./ml. (p < 0.05). Major complications were infrequent, including bladder perforation in 1 patient, urethral strictures in 3, bladder outlet obstruction in 2 and partial incontinence in 2. Impotence was frequent but transient.

CONCLUSIONS

Transrectal ultrasound-guided transperineal percutaneous cryoablation of the prostate produces few major complications and appears at 3 months to be effective in eradicating local prostate tumors. Longer followup is required to test the original hypothesis.

Endosonographic monitoring of transurethral cryoprostatectomy

Cryoprostatectomy, the use of subzero temperatures to ablate prostate tissue gained favour in the 1960s because of its speed and lack of haemodynamic effects. It fell from use because the freezing process could not be monitored and this led to a high incidence of local complications. We have performed transrectal real time ultrasound in 12 patients undergoing cryoprostatectomy. In all the freezing process was easily visualized as an advancing hyperechoic 'iceball' with distal acoustic shadowing. Monitoring allowed maximum prostate ablation without breaching the prostatic capsule. There were no significant complications and all but one patient gained symptomatic relief. Ultrasound at 1 month showed a heterogeneous echo pattern with very little cavity formation but by 3 months a significant cavity was seen. This study demonstrates that it is possible to monitor the freezing process during transurethral cryoprostatectomy. This, theoretically, should significantly reduce the local complications encountered in previous studies.

Transrectal ultrasound-guided percutaneous radical cryosurgical ablation of the prostate

BACKGROUND

The two major treatments for prostate cancer, radical prostatectomy and radiation therapy, are associated with considerable morbidity and variable results. This article presents the preliminary results using percutaneous radical cryosurgical ablation under ultrasound guidance to treat prostate cancer.

METHODS

The patient group consisted of all patients with localized prostate cancer who underwent cryosurgery between June 1, 1990 and May 1, 1992. Patients in Group 1 were treated by freezing of the tumor with two cryoprobes placed multiple times. Group 2 patients were treated by freezing of the tumor with five cryoprobes placed simultaneously. Cryoprobes (3 mm in diameter) were placed percutaneously with a transperineal approach. Cryoprobe placement and freezing were monitored using the transrectal ultrasound.

RESULTS

Of the 55 patients (68 procedures) undergoing treatment, 23 have 3 months of follow-up with associated biopsy (Group 1, 8 patients; Group 2, 15 patients). In Group 1, three (37.5%) patients had residual disease. In Group 2, one (6.7%) patient had residual disease, whereas 14 (93.3%) patients did not. Combining both groups, 19 (82.6%) patients had no residual disease, whereas 4 (17.4%) patients had positive results on postoperative biopsy. Complications included rectal freezing, urethrorectal fistula, sloughing urethral tissue, impotence, perineal ecchymosis, penile edema, and ileus.

CONCLUSIONS

Preliminary results indicate that percutaneous transperineal ultrasound-guided prostate cryosurgery may be an effective treatment for prostate cancer with minimal associated morbidity.

MRI-monitored cryosurgery in the rabbit brain

The inability to observe the transient, irregular shape of the frozen region that develops during cryosurgery has inhibited the application of this surgical technique to the treatment of tumors in the brain and deep in visceral organs. We used proton NMR spin-echo and spoiled gradient-echo imaging to monitor the development of frozen lesions during cryosurgery in the rabbit brain and the resulting postcryosurgical changes up to 4 hr after freezing. Spoiled gradient-echo images (TE = 14 ms; TR = 50 ms) were acquired during freezing and thawing at a rate of 15 s/slice. Although the frozen region itself is invisible in MR images, its presence is distinguished easily from the surrounding unfrozen soft tissue because of the large contrast difference between frozen and unfrozen regions. T2-weighted spin-echo images (TE = 100 ms, TR = 2 s) obtained after thawing suggest that edema forms first at the margin of the region that was frozen (cryolesion) and then moves into the region's core. Histological examination showed complete necrosis in the cryolesion and a sharp transition to undamaged tissue at the margin of the lesion and its image. Blood-brain barrier (BBB) damage was investigated using gadolinium-DTPA. The region of edema in the T2-weighted spin-echo images was coincident with the area of BBB damage in the Gd-DTPA-enhanced T1-weighted spin-echo images (TE = 33 ms, TR = 400 ms) and both were distinguishable as areas of high signal relative to the surrounding normal tissue. The results of these experiments indicate that MR can both effectively monitor the cryosurgical freezing and thawing cycle and characterize the postcryosurgical changes in tissue during follow-up.