Cytoreductive surgery impedes metastasis and enhances the immune response: a preliminary report

Narrative review of local prostate and metastasis-directed radiotherapy in the treatment of metastatic prostate cancer

The role of local treatment in patients with de novo metastatic prostate cancer is controversial. In population-based retrospective studies, metastatic prostate cancer patients who received local treatment with prostate radiotherapy showed a better prognosis than those who did not. In addition, several prospective randomized studies demonstrated that prostate radiotherapy achieves a survival benefit for patients with oligo-metastasis. Moreover, the efficacy of metastasis-directed radiotherapy was evaluated, revealing a potential benefit for patients with oligo-metastasis. Importantly, these radiotherapies may reduce the occurrence of symptomatic local events. In this review, the rationale, efficacy and future perspectives for local prostate and metastasis-directed radiotherapy in the treatment of metastatic prostate cancer were described and summarized.

The cytoreductive prostatectomy in metastatic prostate cancer: what the individual trials are hoping to answer

OBJECTIVE

To review the ongoing randomised trials of cytoreductive prostatectomy (CRP) in de novo hormone-sensitive metastatic prostate cancer (HSPC) in order to identify their goals and assess their strengths and weaknesses.

METHODS

PubMed, MEDLINE and clinical trials websites searches were performed to identify currently ongoing trials of CRP in de novo HSPC.

RESULTS

Nine randomised clinical trials in CRP were identified and included: Southwest Oncology Group (SWOG) 1802, Surgery in Metastatic Carcinoma of Prostate (SIMCAP), Adjuvant Treatments to the Local Tumour for Metastatic Prostate Cancer: Assessment of Novel Treatment Algorithms (IP2-ATLANTA), Testing Radical prostatectomy in men with prostate cancer and oligoMetastases to the bone (TRoMbone), Impact of Radical Prostatectomy as Primary Treatment in Patients with Prostate Cancer with Limited Bone Metastases (g-RAMPP), Cytoreductive Prostatectomy vs Cytoreductive Prostate Irradiation as a Local Treatment Option for Metastatic Prostate Cancer: a Multicentric Feasibility Trial (LoMP II), Androgen-Deprivation Therapy or Androgen-Deprivation Therapy Plus Definitive Treatment (Radiation or Surgery) (FUSCC-OMPCa), and the Testing Radical Prostatectomy in Chinese Men with Prostate Cancer and oligoMetastases to the Bone study. Each study was different; assessing various primary outcome measures including overall survival (OS), progression-free survival and feasibility to randomise between standard therapy and CRP or between radiation therapy and CRP in the metastatic setting. In the oligometastatic setting, the trials assess OS, feasibility to randomise and time to castration resistance. Similarly, a number of secondary endpoints ranging from cancer-specific outcomes to quality-of-life outcomes are being investigated. The inclusion criteria in these trials also varied in terms of volume of metastatic disease (oligometastatic to high-volume metastatic disease), diagnosis of metastases (imaging based vs biopsy confirmed), imaging modalities used (conventional to newer modalities), as well as outcomes and follow-up regimes.

CONCLUSION

While there are differences in each protocol, each trial aims to address different aspects of CRP in de novo HSPC. Therefore, the specific goals of each study and the limitations have to be taken into consideration when interpreting the results of these trials.

Cytoreductive treatment strategies for de novo metastatic prostate cancer

In the past decade, a revolution in the treatment of metastatic prostate cancer has occurred with the advent of novel hormonal agents and life-prolonging chemotherapy regimens in combination with standard androgen-deprivation therapy. Notwithstanding, the use of systemic therapy alone can result in a castrate-resistant state; therefore, increasing focus is being placed on the additional survival benefits that could potentially be achieved with local cytoreductive and/or metastasis-directed therapies. Local treatment of the primary tumour with the established modalities of radiotherapy and radical prostatectomy has been explored in this context, and the use of novel minimally invasive ablative therapies has been proposed. In addition, evidence of the potential clinical benefits of metastasis-directed therapy with ionizing radiation (primarily stereotactic ablative radiotherapy) is accumulating. Herein, we summarize the pathobiological rationale for local cytoreduction and the potentially systemic immunological responses to radiotherapy and ablative therapies in patients with metastatic prostate cancer. We also discuss the current evidence base for a cytoreductive strategy, including metastasis-directed therapy, in the current era of sequential multimodal therapy incorporating novel treatments. Finally, we outline further research questions relating to this complex and evolving treatment landscape.

Effect of Tumor Burden on Tumor Aggressiveness and Immune Modulation in Prostate Cancer: Association with IL-6 Signaling

Local treatment is known to improve survival in men with locally advanced prostate cancer (LAPC), but the underlying mechanisms remain unclear. In the present study, we examined the role of tumor burden in tumor aggressiveness, as well as the pathway responsible for these changes. We used human and murine prostate cancer cell lines to examine the role of tumor burden in tumor aggressiveness, as well as its correlation with cancer stem cell (CSC) marker levels and IL-6 signaling. Furthermore, 167 prostate cancer biopsy specimens were analyzed in terms of correlations of IL-6 and CD44 levels with clinical patient characteristics. Data from preclinical models showed that larger tumor burden was associated with more aggressive tumor growth associated and increased CD44 expression. Using cellular experiments and orthotopic tumor models, we showed that CD44+ prostate cancer cells have CSC-like properties, enhanced epithelial–mesenchymal transition (EMT), and a more immunosuppressive microenvironment. There was a significant correlation between IL-6 and CD44 levels based on in vitro testing of clinical samples. Blockade of IL-6/STAT3 signaling attenuated the expression of CD44, CSC-like properties, and aggressive tumor behavior in vitro and in vivo. In conclusion, CD44 expression is significantly associated with tumor aggressiveness in prostate cancer and activation of IL-6 signaling leads to a suitable microenvironment for the induction of CD44 expression. Based on our study, reduced tumor burden was associated with attenuated IL-6 signaling and augmented tumor rejection in the microenvironment, which might mediate the benefit of clinical adoption with aggressive local therapy.

Treatment of the Primary Tumor in Metastatic Prostate Cancer: Current Concepts and Future Perspectives

CONTEXT

Multimodal treatment for men with locally advanced prostate cancer (PCa) using neoadjuvant/adjuvant systemic therapy, surgery, and radiation therapy is being increasingly explored. There is also interest in the oncologic benefit of treating the primary tumor in the setting of metastatic PCa (mPCa).

OBJECTIVE

To perform a review of the literature regarding the treatment of the primary tumor in the setting of mPCa.

EVIDENCE ACQUISITION

Medline, PubMed, and Scopus electronic databases were queried for English language articles from January 1990 to September 2014. Prospective and retrospective studies were included.

EVIDENCE SYNTHESIS

There is no published randomized controlled trial (RCT) comparing local therapy and systemic therapy to systemic therapy alone in the treatment of mPCa. Prospective studies of men with locally advanced PCa and retrospective studies of occult node-positive PCa have consistently shown the addition of local therapy to a multimodal treatment regimen improves outcomes. Molecular and genomic evidence further suggests the primary tumor may have an active role in mPCa.

CONCLUSIONS

Treatment of the primary tumor in mPCa is being increasingly explored. While preclinical, translational, and retrospective evidence supports local therapy in advanced disease, further prospective studies are under way to evaluate this multimodal approach and identify the patients most likely to benefit from the inclusion of local therapy in the setting of metastatic disease.

PATIENT SUMMARY

In this review we explored preclinical and clinical evidence for treatment of the primary tumor in metastatic prostate cancer (mPCa). We found evidence to support clinical trials investigating mPCa therapy that includes local treatment of the primary tumor. Currently, treating the primary tumor in mPCa is controversial and lacks high-level evidence sufficient for routine recommendation.

Preliminary report of tumor metastasis during liver regeneration after hepatic resection in rats

In an attempt to ascertain possible facilitation of tumor metastasis during liver regeneration after hepatectomy, a series of experiments in rats was carried out using the RBT-1 carcinoma. WKA rats were separated into three groups: Group A received a sham operation; Group B underwent one-third hepatectomy; and Group C underwent two-thirds hepatectomy. Three groups had viable tumor cells injected into the tail vein after treatment. Survival period and lung metastases were analysed 14 days after initial injection of tumor. When comparisons were made between all groups, survival was shown to be significantly shorter in Group C than Group A (P < 0.05). The number of metastatic nodules in the lungs was significantly increased in Group B (P < 0.05) and C (P < 0.01), compared to Group A and in Group C, compared with Group B (P < 0.05). These results suggest that facilitation of tumor metastasis during liver regeneration may be proportional to the extent of liver resection.