Combining energy-based focal ablation and immune checkpoint inhibitors: preclinical research and clinical trials

Energy-based focal therapy (FT) uses targeted, minimally invasive procedures to destroy tumors while preserving normal tissue and function. There is strong emerging interest in understanding how systemic immunity against the tumor can occur with cancer immunotherapy, most notably immune checkpoint inhibitors (ICI). The motivation for combining FT and ICI in cancer management relies on the synergy between the two different therapies: FT complements ICI by reducing tumor burden, increasing objective response rate, and reducing side effects of ICI; ICI supplements FT by reducing local recurrence, controlling distal metastases, and providing long-term protection. This combinatorial strategy has shown promising results in preclinical study (since 2004) and the clinical trials (since 2011). Understanding the synergy calls for understanding the physics and biology behind the two different therapies with distinctive mechanisms of action. In this review, we introduce different types of energy-based FT by covering the biophysics of tissue-energy interaction and present the immunomodulatory properties of FT. We discuss the basis of cancer immunotherapy with the emphasis on ICI. We examine the approaches researchers have been using and the results from both preclinical models and clinical trials from our exhaustive literature research. Finally, the challenges of the combinatory strategy and opportunities of future research is discussed extensively.

Interventional Oncology and Immuno-Oncology: Current Challenges and Future Trends

Personalized cancer treatments help to deliver tailored and biologically driven therapies for cancer patients. Interventional oncology techniques are able to treat malignancies in a locoregional fashion, with a variety of mechanisms of action leading to tumor necrosis. Tumor destruction determines a great availability of tumor antigens that can be recognized by the immune system, potentially triggering an immune response. The advent of immunotherapy in cancer care, with the introduction of specific immune checkpoint inhibitors, has led to the investigation of the synergy of these drugs when used in combination with interventional oncology treatments. The aim of this paper is to review the most recent advances in the field of interventional oncology locoregional treatments and their interactions with immunotherapy.

Immune checkpoint inhibition in early-stage triple-negative breast cancer

INTRODUCTION

Breast cancer cells can evade immune recognition by upregulating programmed death-ligand 1 (PD-L1) leading to decreased T cell function. Anti-PD-1 agents, like pembrolizumab, and anti-PD-L1 agents, such as atezolizumab and durvalumab, in combination with chemotherapy were found to have efficacy in metastatic triple-negative breast cancer (TNBC). With sub-optimal long-term outcomes in early-stage TNBC, this combination of immune checkpoint inhibition with chemotherapy was subsequently investigated. A robust immune microenvironment and extensive tumor antigen exposure in early-stage breast cancer is believed to facilitate response to checkpoint inhibitors.

AREAS COVERED

This review focuses on studies that assess the role of neoadjuvant immune checkpoint inhibition along with chemotherapy. The results of key phase I, II and III trials using checkpoint inhibitors in early-stage breast cancer (ESBC) are reviewed along with foundational data from metastatic TNBC, including the role of biomarkers in predicting response to immunotherapy.

EXPERT OPINION

Despite a clear role for neoadjuvant immune checkpoint inhibition in TNBC, many questions remain. The benefit of these agents in the neoadjuvant versus adjuvant setting is unclear and immune-related toxicity is a major concern. Additional studies are needed to elucidate which immune checkpoint inhibitor is most efficacious and best tolerated in early-stage TNBC.

Current advances in immune checkpoint inhibitor combinations with radiation therapy or cryotherapy for breast cancer

PURPOSE

Immune checkpoint inhibition (ICI) has demonstrated clinically significant efficacy when combined with chemotherapy in triple negative breast cancer (TNBC). Although many patients derived benefit, others do not respond to immunotherapy, therefore relying upon innovative combinations to enhance response. Local therapies such as radiation therapy (RT) and cryotherapy are immunogenic and potentially optimize responses to immunotherapy. Strategies combining these therapies and ICI are actively under investigation. This review will describe the rationale for combining ICI with targeted local therapies in breast cancer.

METHODS

A literature search was performed to identify pre-clinical and clinical studies assessing ICI combined with RT or cryotherapy published as of August 2021 using PubMed and ClinicalTrials.gov.

RESULTS

Published studies of ICI with RT and IPI have demonstrated safety and signals of early efficacy.

CONCLUSION

RT and cryotherapy are local therapies that can be integrated safely with ICI and has shown promise in early trials. Randomized phase II studies testing both of these approaches, such as P-RAD (NCT04443348) and ipilimumab/nivolumab/cryoablation for TNBC (NCT03546686) are current enrolling. The results of these studies are paramount as they will provide long term data on the safety and efficacy of these regimens.

The emerging role of immune checkpoint inhibitors for the treatment of breast cancer

INTRODUCTION

Breast cancer has traditionally been viewed as immunogenically 'cold,' but two immune checkpoint inhibitors have been approved in combination with chemotherapy for PD-L1 positive advanced triple-negative breast cancer (TNBC), and pembrolizumab was also recently approved for early stage TNBC. As the landscape is rapidly evolving, a comprehensive review of checkpoint inhibitors in breast cancer is needed to aid clinicians in selecting appropriate candidates for therapy, and to highlight ongoing promising studies in this area and topics in need of further investigation.

AREA COVERED

This review summarizes the latest evidence from completed and ongoing trials of immune checkpoint inhibitors. Ongoing studies were identified using a search of ClinicalTrials.gov with the term 'breast cancer' along with specific checkpoint inhibitor agents.

EXPERT OPINION

A number of novel combination strategies are under investigation to enhance response and overcome resistance to immunotherapy, with promising preliminary data from checkpoint inhibitors targeting TIGIT, combinations with small molecule inhibitors such as lenvatinib, and injectable agents directly influencing the immune microenvironment. As immunotherapy enters into the curative setting, biomarkers predictive of immunotherapy benefit are needed, as PD-L1 status has not been a helpful discriminator in completed trials in early-stage breast cancer.

Breast Cancer Immunotherapy: From Biology to Current Clinical Applications

Therapeutic strategies for the treatment of breast cancer have historically been determined by the presence or absence of hormone receptors and HER2 amplification and/or protein expression. For patients with breast cancer that lack these biomarkers, the so-called ‘triple-negative’ subtype, chemotherapy has been the cornerstone of cure and palliation. However, with the recent successful development of immune checkpoint molecules that target cytotoxic T-lymphocyte antigen-4, programmed cell death-1 (PD-1), and PD-ligand 1 (PD-L1), improved survival has been reported across a range of tumour types including melanoma, lung, and bladder cancer. In metastatic breast cancer, trials of single-agent immune checkpoint inhibitors (ICI) have resulted in limited overall response rates; however, strategies that combine local or systemic therapies with ICI have improved response rates and, in some cases, improved survival. For example, the addition of an anti-PD-L1 inhibitor, atezolizumab, to nab-paclitaxel chemotherapy for newly diagnosed metastatic triple-negative breast cancer demonstrated an improvement in overall survival in an informal analysis of the PD-L1-positive subset in a recently reported Phase III clinical trial. These results ultimately led to U.S. Food and Drug Administration (FDA) approval for an ICI for the treatment of breast cancer, with numerous other health authorities following suit. Herein, the authors describe the biology behind ICI, the rationale for ICI administration in breast cancer, the related clinical trial data reported to date, and promising future strategies.