Cancer, radiothérapie et système immunitaire

Combination low-dose cyclophosphamide with check-point blockade and ionizing radiation promote an abscopal effect in mouse models of melanoma

PURPOSE

The complex strategy of hypo-fractionated radiotherapy (HFRT) in combination with an immune checkpoint inhibitor (ICI) can stimulate a potential systemic antitumor response; however, the abscopal effect is always precluded by the tumor microenvironment, which may limit sufficient T-cell infiltration of distant nonirradiated tumors for certain kinds of inhibitory factors, such as regulatory T-cells (Tregs). Additionally, low-dose cyclophosphamide (LD-CYC) can specifically kill regulatory Tregs and strongly synergize antigen-specific immune responses, which could promote an abscopal effect.

MATERIALS AND METHODS

We explored whether a triple regimen consisting of HFRT, ICI, and LD-CYC could achieve a better systemic antitumor response in bilateral mouse tumor models.

RESULT

Our data demonstrate that LD-CYC combined with HFRT and antiprogrammed cell death ligand 1 (PDL-1) therapy could enhance the abscopal effect than only HFRT/antiPDL-1 or HFRT alone. Surprisingly, repeat CYC doses cannot further restrain tumor proliferation but can prolong murine overall survival, as revealed by the major pathologic responses. These results are associated with increased CD8 + effector T-cell infiltration, although LD-CYC did not upregulate PDL-1 expression in the tumor.

CONCLUSIONS

Compared with traditional strategies, for the first time, we demonstrated that a triple treatment strategy remarkably increased the number of radiation-induced tumor-infiltrating CD8 + T-cells, effectively decreasing infiltrating Tregs, and promoting an abscopal effect. Thus, we describe a novel and effective therapeutic approach by combining multiple strategies to target several tumor-mediated immune inhibitory mechanisms.

ASSESSMENT OF THE STATE OF IMMUNE SYSTEM IN PATIENTS WITH METASTATIC AND GLIAL BRAIN TUMORS AT THE PREPARATORY STAGE OF RADIOTHERAPY

OBJECTIVE

The aim: To assess the state of the immune system in patients before radiation therapy and radiosurgery and compare the features of immunity in metastatic and glial brain tumors.

PATIENTS AND METHODS

Materials and methods: Our study presents the results of immunograms of 41 patients. Of these: 18 patients with primary glial tumors and 23 patients with secondary metastatic tumors to the brain. The results of 20 conditionally healthy patients who did not have cancer are presented as a control group. The age of patients was 24-75 years. All patients have histological confirmation of the tumor diagnosis. Surgery was performed 1.0-3.0 years before the examination.

RESULTS

Results: When comparing the immune parameters of the number of T and B subpopulations of lymphocytes in patients with primary malignant brain tumors and secondary metastatic tumors, no statistically significant difference was found between these indicators. Glioblastomas show higher levels of IgG and IgA than other tumors, while the concentration of IgM is almost at the same level in all three groups of patients. There is a tendency to decrease the level of IgG and IgM in the blood of patients with metastatic tumors. In the study group of patients there is an inhibition of myeloperoxidase activity of neutrophils on the background of maintaining the function of NBT cell activity.

CONCLUSION

Conclusions: Both metastatic and primary malignant glial have partial changes in various parts of the immune system.

Treatment Strategies for High-Risk Localized and Locally Advanced and Oligometastatic Prostate Cancer

Simple Summary

The definitions of locally advanced and oligometastatic prostate cancer are ambiguous, and there are no standard treatments for these. Although multidisciplinary treatment combining systemic and local treatment may be effective, there are many unresolved issues such as the choice of local treatment, use of new endocrine agents and chemotherapy, and selection of optimal patients. The present article discusses the definitions, diagnoses, and treatment of very high-risk prostate cancer and oligometastatic prostate cancer.

Abstract

Despite the significant advances in the treatment of high-risk prostate cancer, patients with very high-risk features such as being locally advanced (clinical stage T3–4 or minimal nodal involvement), having a high Gleason pattern, or with oligometastasis may still have a poor prognosis despite aggressive treatment. Multidisciplinary treatment with both local and systemic therapies is thought to be effective, however, unfortunately, there is still no standard treatment. However, in recent years, local definitive therapy using a combination of radiotherapy and androgen deprivation is being supported by several randomized clinical trials. This study reviews the current literature with a focus on the definition of very high-risk prostate cancer, the role of modern imaging, and its treatment options.

Spatially Modulated Proton Minibeams Results in the Same Increase of Lifespan as a Uniform Target Dose Coverage in F98-Glioma-Bearing Rats

Proton minibeam radiation therapy (pMBRT) is a new approach in proton radiotherapy, by which a significant increase in the therapeutic index has already been demonstrated in RG2 glioma-bearing rats. In the current study we investigated the response of other types of glioma (F98) and performed a comparative evaluation of tumor control effectiveness by pMBRT (with different levels of dose heterogeneity) versus conventional proton therapy. The results of our study showed an equivalent increase in the lifespan for all evaluated groups (conventional proton irradiation and pMBRT) and no significant differences in the histopathological analysis of the tumors or remaining brain tissue. The reduced long-term toxicity observed with pMBRT in previous evaluations at the same dose suggests a possible use of pMBRT to treat glioma with less side effects while ensuring the same tumor control achieved with standard proton therapy.

Pure abscopal effect of radiotherapy in a salivary gland carcinoma: Case report, literature review, and a search for new approaches

We report the case of an 84-year-old woman with poorly differentiated non-small cell carcinoma of the right parotid who presented with headache, was found to have a primary right parotid gland cancer as well as metastatic disease, and underwent palliative radiotherapy to the primary site. The patient received no chemotherapy or immunotherapy, but both the primary site and several non-irradiated foci in the lungs regressed or completely resolved. The patient remained free of disease for about one year before progression. The case is a rare instance of abscopal regression of metastatic disease in the absence of pharmacologic immunomodulation. A literature review surveys the history of the abscopal effect of radiation therapy, attempts to understand the mechanisms of its successes and failures, and points to new approaches that can inform and improve the outcomes of radioimmunotherapy.

A systematic review of contemporary management of oligometastatic prostate cancer: fighting a challenge or tilting at windmills?

PURPOSE

Amongst the unanswered questions regarding prostate cancer (PCa), the optimal management of oligometastatic disease remains one of the major concerns of the scientific community. The very existence of this category is still subject to controversy. Aim of this systematic review is to summarize current available data on the most appropriate management of oligometastatic PCa.

EVIDENCE ACQUISITION

All relevant studies published in English up to November the 1st were identified through systematic searches in PubMed, EMBASE, Cochrane Library, CINAHL, Google Scholar and Ovid database. A search was performed including the combination of following words: (prostate cancer) and (metastatic) and [(oligo) or (PSMA) or (cytoreductive) or (stereotaxic radiotherapy) or (prostatectomy)]. 3335 articles were reviewed. After title screening and abstract reading, 118 papers were considered for full reading, leaving a total of 36 articles for the systematic review.

EVIDENCE SYNTHESIS

There is still no consensus on the definition of oligometastatic disease, nor on the imaging modalities used for its detection. While retrospective studies suggest an added benefit with the treatment the primitive tumor by cytoreductive prostatectomy (55% survival rate vs 21%, p < 0.001), prospective studies do not validate the same outcome. Nonetheless, most studies have reported a reduction in local complications after cytoreductive prostatectomy (< 10%) compared to the best systemic treatment (25-30%). Concerning radiotherapy, an overall survival benefit for patients with a low metastatic burden was found in STAMPEDE (HR 0.68, 95% CI 0.52-0.90; p = 0.007) and suggested in subgroup analysis of the HORRAD trial. Regarding the impact of metastases-directed therapy (MDT), the STOMP and ORIOLE trials suggested that metastatic disease control might improve androgen deprivation therapy-free survival (in STOMP: 21 vs 13 months for MDT vs standard of care). Nonetheless, the impact of MDT on long-term oncologic results remains unclear. Finally, oligometastatic disease appears to be a biologically different entity compared to high-burden metastatic disease. New findings on exosomes appear to make them intriguing biomarkers in the early phases of oligometastatic PCa.

CONCLUSION

Oligometastatic PCa is today a poorly understood disease. The implementation of new imaging techniques as whole-body MRI and PSMA PET/CT has increased exponentially the number of oligometastatic patients detected. Data of available trials suggest a benefit from cytoreductive prostatectomy to reduce local complication, though its impact on survival remains unknown. Radiotherapy may be beneficial for patients with low-burden metastatic PCa, while MDT may delay the need for androgen deprivation therapy. Results from ongoing trials data are eagerly awaited to draw reliable recommendations.

Proton minibeam radiation therapy widens the therapeutic index for high-grade gliomas

Proton minibeam radiation therapy (pMBRT) is a novel strategy which has already shown a remarkable reduction in neurotoxicity as to compared with standard proton therapy. Here we report on the first evaluation of tumor control effectiveness in glioma bearing rats with highly spatially modulated proton beams. Whole brains (excluding the olfactory bulb) of Fischer 344 rats were irradiated. Four groups of animals were considered: a control group (RG2 tumor bearing rats), a second group of RG2 tumor-bearing rats and a third group of normal rats that received pMBRT (70 Gy peak dose in one fraction) with very heterogeneous dose distributions, and a control group of normal rats. The tumor-bearing and normal animals were followed-up for 6 months and one year, respectively. pMBRT leads to a significant tumor control and tumor eradication in 22% of the cases. No substantial brain damage which confirms the widening of the therapeutic window for high-grade gliomas offered by pMBRT. Additionally, the fact that large areas of the brain can be irradiated with pMBRT without significant side effects, would allow facing the infiltrative nature of gliomas.

p53 and metabolism: from mechanism to therapeutics

The tumor cell changes itself and its microenvironment to adapt to different situations, including action of drugs and other agents targeting tumor control. Therefore, metabolism plays an important role in the activation of survival mechanisms to keep the cell proliferative potential. The Warburg effect directs the cellular metabolism towards an aerobic glycolytic pathway, despite the fact that it generates less adenosine triphosphate than oxidative phosphorylation; because it creates the building blocks necessary for cell proliferation. The transcription factor p53 is the master tumor suppressor; it binds to more than 4,000 sites in the genome and regulates the expression of more than 500 genes. Among these genes are important regulators of metabolism, affecting glucose, lipids and amino acids metabolism, oxidative phosphorylation, reactive oxygen species (ROS) generation and growth factors signaling. Wild-type and mutant p53 may have opposing effects in the expression of these metabolic genes. Therefore, depending on the p53 status of the cell, drugs that target metabolism may have different outcomes and metabolism may modulate drug resistance. Conversely, induction of p53 expression may regulate differently the tumor cell metabolism, inducing senescence, autophagy and apoptosis, which are dependent on the regulation of the PI3K/AKT/mTOR pathway and/or ROS induction. The interplay between p53 and metabolism is essential in the decision of cell fate and for cancer therapeutics.

[Inflammatory and immune biomarkers of radiation response]

In radiotherapy, the treatment is adapted to each individual to protect healthy tissues but delivers most of time a standard dose according to the tumor histology and site. The only biomarkers studied to individualize the treatment are the HPV status with radiation dose de-escalation strategies, and tumor hypoxia with dose escalation to hypoxic subvolumes using FMISO- or FAZA-PET imaging. In the last decades, evidence has grown about the contribution of the immune system to radiation tumor response. Many preclinical studies have identified some of the mechanisms involved. In this context, we have realised a systematic review to highlight potential inflammatory and immune biomarkers of radiotherapy response. Some are inside the tumor microenvironment, as lymphocyte infiltration or PD-L1 expression, others are circulating biomarkers, including different types of hematological cells, cytokines and chemokines.

[Hypofractionated irradiation of prostate cancer: What is the radiobiological understanding in 2017?]

For prostate cancer, hypofractionation has been based since 1999 on radiobiological data, which calculated a very low alpha/beta ratio (1.2 to 1.5Gy). This suggested that a better local control could be obtained, without any toxicity increase. Consequently, two types of hypofractionated schemes were proposed: "moderate" hypofractionation, with fractions of 2.5 to 4Gy, and "extreme" hypofractionation, utilizing stereotactic techniques, with fractions of 7 to 10Gy. For moderate hypofractionation, the linear-quadratic (LQ) model has been used to calculate the equivalent doses of the new protocols. The available trials have often shown a "non-inferiority", but no advantage, while the equivalent doses calculated for the hypofractionated arms were sometimes very superior to the doses of the conventional arms. This finding could suggest either an alpha/beta ratio lower than previously calculated, or a negative impact of other radiobiological parameters, which had not been taken into account. For "extreme" hypofractionation, the use of the LQ model is discussed for high dose fractions. Moreover, a number of radiobiological questions are still pending. The reduced overall irradiation time could be either a positive point (better local control) or a negative one (reduced reoxygenation). The prolonged duration of the fractions could lead to a decrease of efficacy (because allowing for reparation of sublethal lesions). Finally, the impact of the large fractions on the microenvironment and/or immunity remains discussed. The reported series appear to show encouraging short to mid-term results, but the results of randomized trials are still awaited. Today, it seems reasonable to only propose those extreme hypofractionated schemes to well-selected patients, treating small volumes with high-level stereotactic techniques.