Current Status of Salvage Cryoablation for Prostate Cancer following Radiation Failure

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.

Vitamin D(3) cryosensitization increases prostate cancer susceptibility to cryoablation via mitochondrial-mediated apoptosis and necrosis

OBJECTIVES

To investigate the effect and molecular mechanisms of action of Vitamin D(3) (VD(3) ) as a neo-adjunctive agent before cryosurgery in an effort to increase treatment efficacy for prostate cancer (CaP). To eliminate the potential for disease recurrence that exists at the periphery of the freeze lesion, where temperatures may be insufficient to destroy both androgen-sensitive (AS) and androgen-insensitive (AI) CaP.

METHODS

Human CaP cells, LNCaP, were each genetically altered to express the AS and AI phenotypes and subjected to VD(3) treatment and freezing in an in vitro and tissue-engineered model. Cell viability, caspase inhibitor and western blot studies were used to determine the basis of the different responses of AI and AS cells to VD(3) cryosensitization.

RESULTS

VD(3) was found to be a highly effective cryosensitizer, resulting in a >50% overall increase in cell death after -15 °C freezing. Fluorescence microscopy, western blot analysis and caspase protease assays confirmed that the increased activation of apoptosis was modulated through a mitochondrial-mediated pathway. Caspase inhibition studies showed that apoptosis played an integral role in cell death, with VD(3) cryosensitivation-induced apoptotic events responsible for >30% of the overall cell death after -15 °C freezing.

CONCLUSIONS

The present study suggests that the use of VD(3) as a cryosensitizer increases cryoablation efficacy through the increased activity of apoptosis as well as through necrosis. The data show that through VD(3) treatment the overall level of AI CaP cell tolerance to freezing is reduced to a level similar to that of AS CaP. VD(3) pre-treatment in conjunction with cryoablation may increase treatment efficacy and reduce disease recurrence for CaP patients.

Integrin involvement in freeze resistance of androgen-insensitive prostate cancer

Cryoablation has emerged as a primary therapy to treat prostate cancer. While effective, the assumption that freezing serves as a ubiquitous lethal stress is challenged by clinical experience and experimental evidence demonstrating time-temperature related cell death dependence. The age-related transformation from an androgen-sensitive (AS) to an androgen-insensitive (AI) phenotype is a major challenge in the management of prostate cancer. AI cells exhibit morphological changes and treatment resistance to many therapies. Since this resistance has been linked with α6β4 integrin overexpression as a result of androgen receptor (AR) loss, we investigated whether α6β4 integrin expression, as a result AR loss, contributes to the reported increased freeze tolerance of AI prostate cancer. A series of studies using AS (LNCaP LP and PC-3 AR) and AI (LNCaP HP and PC-3) cell lines were designed to investigate the cellular mechanisms contributing to variations in freezing response. Investigation into α6β4 integrin expression revealed that AI cell lines overexpressed this protein, thereby altering morphological characteristics and increasing adhesion characteristics. Molecular investigations revealed a significant decrease in caspase 8, 9, and 3 levels AI cells following freezing. Inhibition of α6β4 integrin resulted in increased caspase activity following freezing (similar to AS cells) and enhanced cell death. These data demonstrate that AI cells show an increase in post-freeze susceptibility following inhibition of α6β4 integrin function. Further understanding the role of androgen-receptor related α6β4 integrin expression in prostate cancer cells responses to freezing might lead to novel options for neo-adjunctive treatments targeting the AR signaling pathway.

Diagnosis of prostatic carcinoma after therapy

CONTEXT

Prostate cancer is the most common cancer of men in the United States and is third only to lung and colon cancer as a cause of cancer death. In 2006, 27,350 Americans will die of prostate cancer, and 234,460 new cases will be diagnosed. Treatment changes in the benign and cancerous prostate create diagnostic challenges in pathologic interpretation, particularly in needle biopsy specimens and in evaluation of extraprostatic metastases.

OBJECTIVE

To summarize therapy-related pathologic findings in the prostate with emphasis on recognition of treated adenocarcinoma.

DATA SOURCES

Extensive review of published literature and the authors' experience.

CONCLUSIONS

Following therapy for prostate cancer, it is critical that the clinician provide the pertinent history of androgen deprivation or radiation therapy to assist the pathologist in rendering the correct diagnosis.

Development of a tissue engineered human prostate tumor equivalent for use in the evaluation of cryoablative techniques

The study of the effectiveness of cryotherapy as a curative treatment for prostate cancer has often relied on the use of either in vitro cell culture monolayers or animal models. While the data gleaned from these studies have been valuable, each model has inherent limitations. In order to bridge the gap between in vitro studies and clinical applications, we developed a 3-dimensional, tissue engineered human prostate cancer model to simulate and assess the effects of cryotherapy and adjunctive treatments on cell viability and activation of cell death pathways throughout the thermally variable freeze zone. Human prostate cancer cells (PC3) were seeded into collagen based matrices and cryolesions were generated using an Oncura SeedNet Gold cryosurgical device with 17-gauge cryoprobes. Analyses revealed widespread necrosis diminishing towards the edge of the freeze zone, and a time-dependent wave of apoptosis starting as early as 1 hr post-thaw at low temperatures (< -40 degrees C) and moving toward the periphery (-20 degrees C) as recovery times reached 12 and 24 hr. Distal to the -10 degrees C isotherm, minimal cell death was apparent (< 20%) over controls. The adjunctive use of chemotherapeutic agents in conjunction with cryosurgery displayed a similar induction of cell death cascades, but with the zone of cryodestruction extending approximately 10 to 15 degrees C further into the freeze zone periphery. By providing an extracellular environment and a matrix to minimize innate variables, the tissue engineered model yielded a more in vivo-like, tumor-like environment supportive of a deeper understanding of the specific biological responses of cancer cells/tumors to cryotherapeutic intervention.

Locally ablative therapies for primary radiation failures: a review and critical assessment of the efficacy

A significant number of men with prostate cancer will experience biochemical failure following treatment with primary radiation therapy. For patients with biopsy-proven recurrent cancer confined to the prostate, local salvage therapy may be a potentially curative treatment option. Most men, however, do not undergo local salvage therapy owing to difficulties in diagnosis as well as concerns over treatment-related complications in the salvage setting. Recently, improvements in technique and technology have substantially reduced the morbidity associated with locally ablative therapies, resulting in an increased interest in the use of minimally invasive therapies such as brachytherapy, cryotherapy, and high-intensity focused ultrasound in the salvage setting. Although these treatments are well tolerated, concerns remain over incomplete and inadequate treatment with locally ablative therapies. Future studies are required to appropriately select candidates for salvage ablative therapies and to determine the long-term oncologic efficacy of these treatments.

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.

Minimally Invasive Approaches to Localized Prostate Carcinoma

Prostate cancer is an increasing medical problem. Radical prostatectomy and radiation therapy are effective treatments, but have the risk of significant morbidity. Clinicians have strived to develop new modalities of treatment that can maintain the excellent treatment outcomes of radical prostatectomy, but diminish the morbidity. Improved instrumentation, optics, and robotic technology have allowed the application of laparoscopic techniques to radical prostatectomy. Patients can have less blood loss and expect more rapid recovery. Intermediate oncologic outcomes appear similar to radical prostatectomy with good functional results. Cryotherapy and HIFU are tissue ablative approaches rather than extirpative approaches to prostate cancer treatment. They attempt to use nonsurgical methods to treat prostate cancer with the hope of providing oncologic control comparable to surgery and radiation while minimizing morbidity.

Sustained long-term immune responses after in situ gene therapy combined with radiotherapy and hormonal therapy in prostate cancer patients

PURPOSE

To explore long-term immune responses after combined radio-gene-hormonal therapy.

METHODS AND MATERIALS

Thirty-three patients with prostate specific antigen 10 or higher or Gleason score of 7 or higher or clinical stage T2b to T3 were treated with gene therapy that consisted of 3 separate intraprostatic injections of AdHSV-tk on Days 0, 56, and 70. Each injection was followed by 2 weeks of valacyclovir. Intensity-modulated radiation therapy was delivered 2 days after the second AdHSV-tk injection for 7 weeks. Hormonal therapy was initiated on Day 0 and continued for 4 months or 2.3 years. Blood samples were taken before, during, and after treatment. Lymphocytes were analyzed by fluorescent antibody cell sorting (FACS).

RESULTS

Median follow-up was 26 months (range, 4-48 months). The mean percentages of DR+CD8+ T cells were increased at all timepoints up to 8 months. The mean percentages of DR+CD4+ T cells were increased later and sustained longer until 12 months. Long-term (2.3 years) use of hormonal therapy did not affect the percentage of any lymphocyte population.

CONCLUSIONS

Sustained long-term (up to 8 to 12 months) systemic T-cell responses were noted after combined radio-gene-hormonal therapy for prostate cancer. Prolonged use of hormonal therapy does not suppress this response. These results suggest the potential for sustained activation of cell-mediated immune responses against cancer.