Challenges and opportunities of using stereotactic body radiotherapy with anti-angiogenesis agents in tumor therapy

Comparison of stereotactic body radiation therapy with hepatic resection and radiofrequency ablation as initial treatment in patients with early-stage hepatocellular carcinoma

BACKGROUND

Stereotactic body radiation therapy (SBRT) has emerged as a novel intervention for early-stage hepatocellular carcinoma (HCC). The outcomes of SBRT, liver resection (LR), and radiofrequency ablation (RFA) as the initial treatment for AJCC stage I HCC patients remain unclear.

METHODS

Patients with AJCC stage I HCC from the Surveillance, Epidemiology and End Results database were analyzed for survival rates using the Kaplan-Meier method and stratified according to tumor size: S subgroup (≤2 cm), M subgroup (>2-3 cm), and L subgroup (>3 cm). For factors including age, year of diagnosis, sex, race, grade, tumor size, AFP, and fibrosis score, propensity score matching was performed to eliminate the imbalance of baseline features and selection bias during groups.

RESULTS

A total of 4,002 patients were included; the difference in median overall survival (mOS) between the SBRT group and the LR or RFA group in the S subgroup was statistically insignificant (p=0.109 and p=0.744), while that of the RFA group was significantly worse than that of the LR group (p <0.001). In the M and L subgroups, the mOS of the SBRT group was worse than that of the RFA group (p=0.040 and p<0.001, respectively). The mOS of LR was the best when compared with either the SBRT or RFA group regardless of the subgroup M or L (all p<0.001).

CONCLUSION

For HCC ≤ 2 cm, SBRT can be used as an alternative treatment for RFA. For patients with HCC larger than 2 cm, RFA can provide better long-term survival than SBRT, while LR remains the best choice.

Radiotherapy plus CAR-T cell therapy to date: A note for cautions optimism?

Radiotherapy (RT) is a traditional therapeutic regime that focuses on ionizing radiation, however, RT maintains largely palliative due to radioresistance. Factors such as hypoxia, the radiosensitivity of immune cells, and cancer stem cells (CSCs) all come into play in influencing the significant impact of radioresistance in the irradiated tumor microenvironment (TME). Due to the substantial advances in the treatment of malignant tumors, a promising approach is the genetically modified T cells with chimeric antigen receptors (CARs) to eliminate solid tumors. Moreover, CAR-T cells targeting CSC-related markers would eliminate radioresistant solid tumors. But solid tumors that support an immune deserted TME, are described as immunosuppressive and typically fail to respond to CAR-T cell therapy. And RT could overcome these immunosuppressive features; thus, growing evidence supports the combination of RT with CAR-T cell therapy. In this review, we provide a deep insight into the radioresistance mechanisms, advances, and barriers of CAR-T cells in response to solid tumors within TME. Therefore, we focus on how the combination strategy can be used to eliminate these barriers. Finally, we show the challenges of this therapeutic partnership.

Sesamin inhibits hypoxia-stimulated angiogenesis via NF-κB p65/HIF-1α/VEGFA signaling pathway in human colorectal cancer

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths. Tumor angiogenesis plays a critical role in CRC metastasis, and hypoxia, widely existed in the tumor mass, drives tumor...

Angiogenesis and immune checkpoint dual blockade in combination with radiotherapy for treatment of solid cancers: opportunities and challenges

Several immune checkpoint blockades (ICBs) capable of overcoming the immunosuppressive roles of the tumor immune microenvironment have been approved by the US Food and Drug Administration as front-line treatments of various tumor types. However, due to the considerable heterogeneity of solid tumor cells, inhibiting one target will only influence a portion of the tumor cells. One way to enhance the tumor-killing efficiency is to develop a multiagent therapeutic strategy targeting different aspects of tumor biology and the microenvironment to provide the maximal clinical benefit for patients with late-stage disease. One such strategy is the administration of anti-PD1, an ICB, in combination with the humanized monoclonal antibody bevacizumab, an anti-angiogenic therapy, to patients with recurrent/metastatic malignancies, including hepatocellular carcinoma, metastatic renal cell carcinoma, non-small cell lung cancer, and uterine cancer. Radiotherapy (RT), a critical component of solid cancer management, has the capacity to prime the immune system for an adaptive antitumor response. Here, we present an overview of the most recent published data in preclinical and clinical studies elucidating that RT could further potentiate the antitumor effects of immune checkpoint and angiogenesis dual blockade. In addition, we explore opportunities of triple combinational treatment, as well as discuss the challenges of validating biomarkers and the management of associated toxicity.

Monotherapy and Combination Therapy Using Anti-Angiogenic Nanoagents to Fight Cancer

Anti-angiogenic therapy, targeting vascular endothelial cells (ECs) to prevent tumor growth, has been attracting increasing attention in recent years, beginning with bevacizumab (Avastin) through its Phase II/III clinical trials on solid tumors. However, these trials showed only modest clinical efficiency; moreover, anti-angiogenic therapy may induce acquired resistance to the drugs employed. Combining advanced drug delivery techniques (e.g., nanotechnology) or other therapeutic strategies (e.g., chemotherapy, radiotherapy, phototherapy, and immunotherapy) with anti-angiogenic therapy results in significantly synergistic effects and has opened a new horizon in fighting cancer. Herein, clinical difficulties in using traditional anti-angiogenic therapy are discussed. Then, several promising applications of anti-angiogenic nanoagents in monotherapies and combination therapies are highlighted. Finally, the challenges and perspectives of anti-angiogenic cancer therapy are summarized. A useful introduction to anti-angiogenic strategies, which may significantly improve therapeutic outcomes, is thus provided.

Advances in Hypofractionated Irradiation-Induced Immunosuppression of Tumor Microenvironment

Hypofractionated radiotherapy is external beam irradiation delivered at higher doses in fewer fractions than conventional standard radiotherapy, which can stimulate innate and adaptive immunity to enhance the body’s immune response against cancer. The enhancement effect of hypofractionated irradiation to immune response has been widely investigated, which is considered an approach to expand the benefit of immunotherapy. Meanwhile, increasing evidence suggests that hypofractionated irradiation may induce or enhance the suppression of immune microenvironments. However, the suppressive effects of hypofractionated irradiation on immunomicroenvironment and the molecular mechanisms involved in these conditions are largely unknown. In this context, we summarized the immune mechanisms associated with hypofractionated irradiation, highlighted the advances in its immunosuppressive effect, and further discussed the potential mechanism behind this effect. In our opinion, besides its immunogenic activity, hypofractionated irradiation also triggers homeostatic immunosuppressive mechanisms that may counterbalance antitumor effects. And this may suggest that a combination with immunotherapy could possibly improve the curative potential of hypofractionated radiotherapy.

Dosimetric evaluation of SBRT treatment plans of non-central lung tumours: clinical experience

Objectives:

Lung cancer is the most commonly diagnosed cancer in Canada and the leading cause of cancer-related mortality in both men and women in North America. Surgery is usually the primary treatment option for early-stage non-small cell lung cancer (NSCLC). However, for patients who may not be suitable candidates for surgery, stereotactic body radiation therapy (SBRT) is an alternative method of treatment. SBRT has proven to be an effective technique for treating NSCLC patients by focally administering high radiation dose to the tumour with acceptable risk of toxicity to surrounding healthy tissues. The goal of this comprehensive retrospective dosimetric study is to compare the dosimetric parameters between three-dimensional conformal radiation therapy (3DCRT) and volumetric-modulated arc therapy (VMAT) lung SBRT treatment plans for two prescription doses.

Methods:

We retrospectively analysed and compared lung SBRT treatment plans of 263 patients treated with either a 3DCRT non-coplanar or with 2–3 VMAT arcs technique at 48 Gy in 4 fractions (48 Gy/4) or 50 Gy in 5 fractions (50 Gy/5) prescribed to the planning target volume (PTV), typically encompassing the 80% isodose volume. All patients were treated on either a Varian 21EX or TrueBeam linear accelerator using 6-MV or 10-MV photon beams.

Results:

The mean PTV V95% and V100% for treatment plans at 48 Gy/4 are 99·4 ± 0·6% and 96·0 ± 1·0%, respectively, for 3DCRT and 99·7 ± 0·4% and 96·4 ± 3·4%, respectively, for VMAT. The corresponding mean PTV V95% and V100% at 50 Gy/5 are 99·0 ± 1·4% and 95·5 ± 2·5% for 3DCRT and 99·5 ± 0·8% and 96·1 ± 1·6% for VMAT. The CIRI and HI5/95 for the PTV at 48 Gy/4 are 1·1 ± 0·1 and 1·2 ± 0·0 for 3DCRT and 1·0 ± 0·1 and 1·2 ± 0·0 for VMAT. The corresponding CIRI and HI5/95 at 50 Gy/5 are 1·1 ± 0·1 and 1·3 ± 0·1 for 3DCRT and 1·0 ± 0·1 and 1·2 ± 0·0 for VMAT. The mean R50% and D2cm at 48 Gy/4 are 5·0 ± 0·8 and 61·2 ± 7·0% for 3DCRT and 4·9 ± 0·8 and 57·8 ± 7·9% for VMAT. The corresponding R50% and D2cm at 50 Gy/5 are 4·7 ± 0·5 and 65·5 ± 9·4% for 3DCRT and 4·7 ± 0·7 and 60·0 ± 7·2% for VMAT.

Conclusion:

The use of 3DCRT or VMAT technique for lung SBRT is an efficient and reliable method for achieving dose conformity, rapid dose fall-off and minimising doses to the organs at risk. The VMAT technique resulted in improved dose conformity, rapid dose fall-off from the PTV compared to 3DCRT, although the magnitude may not be clinically significant.

Radiobiology of stereotactic ablative radiotherapy (SABR): perspectives of clinical oncologists

Stereotactic ablative radiotherapy (SABR) is a novel radiation treatment method that delivers an intense dose of radiation to the treatment targets with high accuracy. The excellent local control and tolerance profile of SABR have made it become an important modality in cancer treatment. The radiobiology of SABR is a key factor in understanding and further optimizing the benefits of SABR. In this review, we have addressed several issues in the radiobiology of SABR from the perspective of clinical oncologists. The appropriateness of the linear-quadratic (LQ) model for SABR is controversial based on preclinical data, but it is a reliable tool from the perspective of clinical application because the biological effective dose (BED) calculated with it can represent the tumor control probability (TCP). Hypoxia is a common phenomenon in SABR in spite of the relatively small tumor size and has a negative effect on the efficacy of SABR. Preliminary studies indicate that a hypoxic radiosensitizer combined with SABR may be a feasible strategy, but so far there is not adequate evidence to support its application in routine practice. The vascular change of endothelial apoptosis and blood perfusion reduction in SABR may enhance the response of tumor cells to radiation. Combination of SABR with anti-angiogenesis therapy has shown promising efficacy and good tolerance in advanced cancers. SABR is more powerful in enhancing antitumor immunity and works better with immune checkpoint inhibitors (ICIs) than conventional fractionation radiotherapy. Combination of SABR with ICIs has become a practical option for cancer patients with metastases.

Apatinib as targeted therapy for advanced bone and soft tissue sarcoma: a dilemma of reversing multidrug resistance while suffering drug resistance itself

Bone and soft tissue sarcomas are rare malignant tumors originated from mesenchymal tissues. They harbor more than 50 distinct subtypes and differ in pathological features and clinical courses. Despite the significant improvements in modern multi-modality treatment, the outcomes and overall survival rates remain poor for patients with advanced, refractory, metastatic, or relapsed diseases. The growth and metastasis of bone and soft tissue sarcoma largely depend on angiogenesis, and VEGF/VEGFR pathway is considered as the most prominent player in angiogenesis. Therefore, blockade of VEGF/VEGFR pathways is a promising therapeutic strategy to retard neovascularization. Several VEGFR inhibitors have been developed and revealed their favorable anti-neoplastic effects in various cancers, but such desirable anti-tumor effects are not obtained in advanced sarcomas because of multiple reasons, such as drug tolerance, short duration of response, and severe adverse effects. Fortunately, preclinical and clinical studies have indicated that apatinib is a novel promising VEGFR2 inhibitor showing potent anti-angiogenic and anti-neoplastic activities in advanced sarcomas. Especially, apatinib has showed notable characteristics in multidrug resistance reversal, tumor regression, vascular normalization, immunosuppression alleviation, and enhancement of chemotherapeutic and radiotherapeutic effects. However, apatinib also gets struck in dilemma of reversing multidrug resistance of chemotherapeutic agents while suffering drug resistance itself, and several difficulties should be tackled before full use of apatinib. In this review, we discuss the outstanding characteristics and main predicaments of apatinib as targeted therapy in advanced sarcomas. Bone and soft tissue sarcomas are rare but malignant tumors originated from mesenchymal tissues. They harbor more than 100 distinct subtypes and differ in features of pathologies and clinical courses. Despite the significant improvements in modern multi-modality treatment, the outcomes and overall survival rates remain poor for patients with advanced, refractory, metastatic, or relapsed lesions. The growth and metastasis of bone and soft tissue sarcoma largely depend on angiogenesis and VEGF/VEGFR pathways play a pivotal role in angiogenesis. Therefore, blockade of VEGF/VEGFR pathways is a promising therapeutic strategy. Several VEGFR inhibitors have been developed and verified in clinical trials but with unfavorable outcomes. Fortunately, preclinical studies and clinical trials have indicated that apatinib is a novel promising VEGFR2 inhibitor showing potent anti-angiogenic and anti-neoplastic activities in advanced sarcomas. Actually, apatinib has showed notable characteristics in multidrug resistance reversal, tumor regression, vascular normalization, immunosuppression alleviation, enhancement of chemotherapeutic and radiotherapeutic effects. However, apatinib also gets struck in dilemma of reversing multidrug resistance of chemotherapeutic agents while suffering drug resistance itself, and several difficulties should be tackled before full use of apatinib. In this review, we discuss the outstanding characteristics and main predicaments of apatinib as targeted therapy in advanced sarcomas.

Integration of stereotactic radiosurgery or whole brain radiation therapy with immunotherapy for treatment of brain metastases

The prognosis of brain metastases (BM) is traditionally poor. BM are mainly treated by local radiotherapy, including stereotactic radiosurgery (SRS) or whole brain radiation therapy (WBRT). Recently, immunotherapy (i.e., immune checkpoint inhibitors, ICI) has demonstrated a survival advantage in multiple malignancies commonly associated with BM. Individually, radiotherapy and ICI both treat BM efficiently; hence, their combination seems logical. In this review, we summarize the existing preclinical and clinical evidence that supports the applicability of radiotherapy as a sensitizer of ICI for BM. Further, we discuss the optimal timing at which radiotherapy and ICI should be administered and review the safety of the combination therapy. Data from a few clinical studies suggest that combining SRS or WBRT with ICI simultaneously rather than consecutively potentially enhances brain abscopal-like responses and survival. However, there is a lack of conclusion about the definition of "simultaneous"; the cumulative toxic effect of the combined therapies also requires further study. Thus, ongoing and planned prospective trials are needed to further explore and validate the effect, safety, and optimal timing of the combination of immunotherapy with radiotherapy for patients with BM.

Combination with Stereotactic Body Radiotherapy Offers a Promising Strategy to Overcome Resistance to Immunotherapy in Advanced Renal Cell Cancer

Immunotherapy for renal cell cancer (RCC) has witnessed several developments for more than two decades. Checkpoint inhibitors, including anti-CTLA-4 and anti-PD-1/PD-L1 blockers, have changed the treatment landscape for patients with advanced RCC in the past 3 years. Despite these advances, more than 55% RCC patients become resistant to different immunotherapies without other treatment combination. Among various attempts at overcoming resistance to immunotherapy, stereotactic body radiotherapy (SBRT) has been found to potentiate the activity of immunotherapy agents through several potential mechanisms, including normalization of microvessels to alleviate tumor hypoxia, improvement in efficient delivery of drugs, abundant neoantigen exposure, and recruitment of antitumor immune cells to alter the immunosuppressive tumor microenvironment. Preclinical studies and clinical case reports have predicted that the combination of SBRT, an immunotherapy, may lead to remarkable results. This review aims to provide the biological basis for the feasibility of combining SBRT to overcome immunotherapy resistance and to review the currently available clinical evidence of this combination therapy in patients with advanced RCC.

Tumor Microenvironment as A "Game Changer" in Cancer Radiotherapy

Radiotherapy (RT), besides cancer cells, also affects the tumor microenvironment (TME): tumor blood vessels and cells of the immune system. It damages endothelial cells and causes radiation-induced inflammation. Damaged vessels inhibit the infiltration of CD8+ T lymphocytes into tumors, and immunosuppressive pathways are activated. They lead to the accumulation of radioresistant suppressor cells, including tumor-associated macrophages (TAMs) with the M2 phenotype, myeloid-derived suppressor cells (MDSCs), and regulatory T cells (Tregs). The area of tumor hypoxia increases. Hypoxia reduces oxygen-dependent DNA damage and weakens the anti-cancer RT effect. It activates the formation of new blood vessels and leads to cancer relapse after irradiation. Irradiation may also activate the immune response through immunogenic cell death induction. This leads to the "in situ" vaccination effect. In this article, we review how changes in the TME affect radiation-induced anticancer efficacy. There is a very delicate balance between the activation of the immune system and the immunosuppression induced by RT. The effects of RT doses on immune system reactions and also on tumor vascularization remain unclear. A better understanding of these interactions will contribute to the optimization of RT treatment, which may prevent the recurrence of cancer.

Ionizing radiation exposure: hazards, prevention, and biomarker screening

Radiation is a form of energy derived from a source that is propagated through material in space. It consists of ionizing radiation or nonionizing radiation. Ionizing radiation is a feature of the environment and an important tool in medical treatment, but it can cause serious damage to organisms. A number of protective measures and standards of protection have been proposed to protect against radiation. There is also a need for biomarkers to rapidly assess individual doses of radiation, which can not only estimate the dose of radiation but also determine its effects on health. Proteomics, genomics, metabolomics, and lipidomics have been widely used in the search for such biomarkers. These topics are discussed in depth in this review.