Turning Radiotherapy into an Effective Systemic Anti-cancer Treatment in Combination with Immunotherapy

Where is clinical research for radiotherapy going? Cross-sectional comparison of past and contemporary phase III clinical trials

Purpose

The features of past and contemporary phase III clinical trials for radiotherapy were reviewed to activate future clinical trials and to advise on actual clinical practice.

Methods and materials

The phase III clinical trials for radiotherapy were searched in the database of ‘ClinicalTrials.gov’ by the U.S. National Institute of Health. Using the staring date, the studies during each period of 4 years were collected for the past (from Jan 2000 to Dec 2003) and contemporary (July 2014 to June 2018) years. For the investigated subjects, the patterns of studies were classified as: Category A, the comparisons of rival radiotherapy protocols; Category B, the comparisons of multidisciplinary approaches; Category C, the investigation of supplementary agents; and Category D, the investigation of optimal partners for concurrent radiotherapy.

Results

The number of studies increased, from 96 past to 158 contemporary studies. The patterns of studies were similar with the mild increase of Category A in the contemporary years (22.9% vs. 29.1%). For the study locations and the funding sources, the Chinese studies (2.1% vs. 34.2%, P < 0.001) and the affiliated institutions of researchers (37.5% vs. 72.2%, P < 0.001) markedly increased in the contemporary years from the past Western studies and non-profit organization, respectively. The robust radiation techniques were more usual in the contemporary years (11.5% vs. 44.9%, P < 0.001). The fractionation schedule and delivery technique were the common issues in both past and contemporary years of Category A. In Category B, the indications of stereotactic radiotherapy was the rising concern, with eight ongoing studies. Except for the studies of palliative or prophylactic goals and stereotactic radiotherapy, the escape from conventional fraction size was 37.9% (36/95) in the contemporary years with the median fraction size of 2.5 Gy (range 2.05–6.6 Gy) in the comparison with 19.0% (15/79) in the past years (P = 0.006).

Conclusions

To activate the clinical trials for radiotherapy, the funding sources would be diversified, including industrial support. Hypofractionated schedules using robust techniques could be preemptively considered in actual clinical practice.

Targeting Immune Checkpoints in Lung Cancer: Current Landscape and Future Prospects

Lung cancer is the most prevalent and deadly cancer worldwide. Immune checkpoint therapy, which targets regulatory pathways in T cells to boost anti-tumor immune response, has revolutionized lung cancer treatment paradigms. Inhibitors of the most established immune checkpoints such as programmed death-1 (PD-1)/PD-ligand 1 (PD-L1) have been approved by the US Food and Drug Administration in the management of lung cancer. Despite the pronounced survival benefits that have been seen with immune checkpoint inhibitors, not all lung cancer patients respond to single-agent immunotherapy due to the complexity of the immune microenvironment and tumor resistance. Alternative immune checkpoints beyond PD-1/PD-L1 must be sought so that more patients can benefit from immune checkpoint therapy. Additionally, novel combination strategies of immunotherapy and conventional treatments (e.g., chemotherapy, radiotherapy, and targeted therapy) have shown promise in some clinical trials. Meanwhile, identification of predictive biomarkers is pivotal in selecting eligible patients for immunotherapy and to guide individualized clinical decision-making. The future of immune checkpoint therapy in lung cancer is not devoid of challenges, and more prospective clinical studies are awaited to translate our understanding from bench to bedside.

Immune Checkpoint Inhibitors in Lung Cancer - An Unheralded Opportunity?

Lung cancer remains the leading cause of cancer-related death worldwide, with non-small cell lung cancer accounting for 85% of the disease. Over 70% of patients present with locally advanced, non-resectable or metastatic disease and despite improvements in chemoradiotherapy regimens and the development of molecularly targeted agents, 5 year survival rates remain poor, with acquired resistance to novel targeted therapies becoming a growing concern. Currently there remains an unmet need in effectively treating and inducing durable responses in advanced disease. Targeting the immune system has, however, recently given hope of improving therapeutic outcomes for these patients. The notion that the immune system is capable of recognising and eliminating cancer cells is now a widely accepted phenomenon and growing evidence suggests lung cancer is an attractive target for such intervention. Recent success targeting the programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) axis of immune checkpoint inhibition suggests a major immunotherapeutic advance in treating lung cancer and unheralded opportunity for such approaches to further improve outcome for patients. Currently there is considerable interest in combining anti-PD-1 or PD-L1 monoclonal antibodies with established standard of care therapies such as radiotherapy. Radiotherapy is known to be immunostimulatory and efforts are underway to combine and augment the efficacy of the immune checkpoint inhibitors further. This review outlines the interaction between lung cancer and the immune system, summarises current evidence supporting the use of monoclonal antibodies targeting the PD-1 axis in lung cancer and explores the potential of combining radiotherapy with immunotherapy to augment anti-tumour immune responses.

Clinical development of new drug-radiotherapy combinations

In countries with the best cancer outcomes, approximately 60% of patients receive radiotherapy as part of their treatment, which is one of the most cost-effective cancer treatments. Notably, around 40% of cancer cures include the use of radiotherapy, either as a single modality or combined with other treatments. Radiotherapy can provide enormous benefit to patients with cancer. In the past decade, significant technical advances, such as image-guided radiotherapy, intensity-modulated radiotherapy, stereotactic radiotherapy, and proton therapy enable higher doses of radiotherapy to be delivered to the tumour with significantly lower doses to normal surrounding tissues. However, apart from the combination of traditional cytotoxic chemotherapy with radiotherapy, little progress has been made in identifying and defining optimal targeted therapy and radiotherapy combinations to improve the efficacy of cancer treatment. The National Cancer Research Institute Clinical and Translational Radiotherapy Research Working Group (CTRad) formed a Joint Working Group with representatives from academia, industry, patient groups and regulatory bodies to address this lack of progress and to publish recommendations for future clinical research. Herein, we highlight the Working Group's consensus recommendations to increase the number of novel drugs being successfully registered in combination with radiotherapy to improve clinical outcomes for patients with cancer.

Background and Current Treatment of Squamous Cell Carcinoma of the Anus

In this review, a summary of our current understanding of squamous cell carcinoma of the anus (SCCA) and the advances in our knowledge of SCCA regarding screening, prevention, the role of the immune system, current treatment and the potential for novel targets are discussed. The present standard of care in terms of treatment is 5-fluorouracil (5-FU) and mitomycin C (MMC) concurrently with radiation, which results in a high level of disease control for small early cancers. Preservation of the anal sphincter is achieved in the majority, although anorectal function is often impaired. Although evidence from prospective studies to support a change in the treatment strategy is lacking, patients with HPV-negative SCCA appear to be less responsive to chemoradiation (CRT) and relapse more frequently. In contrast, HPV-positive tumours usually fare better, but oncological outcomes are modified by smoking and immune incompetence. There is current interest in escalating the radiotherapy dose for larger, more advanced tumours, and de-escalating treatment for HPV-positive tumours. The use of novel immunological treatments to target the underlying different molecular pathways of HPV-positive cancers is exciting.

Anal cancer - What is the optimum chemoradiotherapy?

Radical concurrent chemoradiotherapy with 5FU and Mitomycin C is the standard-of-care for squamous-cell carcinoma of the anus (SCCA). Phase III trials combined radiation doses of 50-60 Gy with concurrent Fluoropyrimidines, Mitomycin C and Cisplatin in various doses and schedules. CRT is highly successful for early T1/T2 cancers, but results in appreciable late morbidities and still fails to control larger and node-positive tumours. Compliance to chemotherapy is important for local control. Modern radiotherapy techniques such as intensity-modulated radiotherapy (IMRT), rotational IMRT, image-guided radiotherapy (IGRT) have enabled smaller margins and highly conformal plans, resulting in decreased radiation doses to the organs at risk and ensuring a shorter overall treatment time. These advances offer the potential for integrating higher doses of radiation, escalation of the currently used drugs and the safe use of other more novel agents with acceptable toxicity. In this chapter potential novel approaches are discussed in the context of SCCA.

Potentiating Cancer Immunotherapy Using Papaya Mosaic Virus-Derived Nanoparticles

The recent development of novel immunotherapies is revolutionizing cancer treatment. These include, for example, immune checkpoint blockade, immunomodulation, or therapeutic vaccination. Although effective on their own, combining multiple approaches will most likely be required in order to achieve the maximal therapeutic benefit. In this regard, the papaya mosaic virus nanoparticle (PapMV) has shown tremendous potential as (i) an immunostimulatory molecule, (ii) an adjuvant, and (iii) a vaccine platform through its intrinsic capacity to activate the innate immune response in an IFN-α-dependent manner. Here, we demonstrate that intratumor administration of PapMV significantly slows down melanoma progression and prolongs survival. This correlates with enhanced chemokine and pro-inflammatory-cytokine production in the tumor and increased immune-cell infiltration. Proportions of total and tumor-specific CD8(+) T cells dramatically increase following PapMV treatment whereas those of myeloid-derived suppressor cells (MDSC) concomitantly decrease. Moreover, systemic PapMV administration prevents metastatic tumor-implantation in the lungs. Importantly, PapMV also synergistically improves the therapeutic benefit of dendritic cell (DC)-based vaccination and PD-1 blockade by potentiating antitumor immune responses. This study illustrates the immunostimulatory potential of a plant virus-derived nanoparticle for cancer therapy either alone or in conjunction with other promising immunotherapies in clinical development.

Tumour-infiltrating lymphocyte scores effectively stratify outcomes over and above p16 post chemo-radiotherapy in anal cancer

Background:

The majority (90%) of anal cancers are human papillomavirus (HPV)-driven, identified using immunochemistry for p16. Compared with HPV− patients, those with HPV+ disease generally show improved survival, although relapse rates around 25% indicate a need for further stratification of this group.

Methods:

Using two cohorts of anal cancer, previously characterised for p16, we assessed the prognostic value of tumour-infiltrating lymphocytes (TILs).

Results:

Tumour-infiltrating lymphocyte scores were used to stratify p16+ cases, where tumours with absent/low levels of TIL had a relapse-free rate of 63%, as opposed to 92% with high levels of TIL (log rank P=0.006).

Conclusions:

Assessment of TIL adds to p16 status in the prognosis of anal cancer following chemo-radiotherapy and provides evidence of the clinical importance of the immune response.