The development of stereotactic body radiotherapy in the past decade: a global perspective

Preoperative stereotactic body radiotherapy combined with surgical treatment for renal cell carcinoma and inferior vena cava tumour thrombus: study protocol for a single-arm cohort trial

INTRODUCTION

Although surgery is currently the first choice for patients with renal cell carcinoma and vena cava tumour thrombus, the surgery is difficult, with many complications, and the prognosis of patients is not ideal. Renal cell carcinoma is not sensitive to traditional radiotherapy, but the development of stereotactic ablative body radiotherapy (SABR) technology with the characteristics of high precision, dose and conformity has made the radiotherapy of renal cell carcinoma reexamined.

METHODS AND ANALYSIS

STUDY DESIGN: This trial is a single-arm cohort study sponsored by Peking University Third Hospital.

STUDY TREATMENT

Preoperative stereotactic ablative radiotherapy combined with surgical treatment. PRIMARY ENDPOINTS: (1) Adverse reactions after 4-6 weeks of SABR. (2) Mayo staging of tumour thrombus. (3) The length of the tumour thrombus from the corresponding anatomical mark. (4) Invasion of the inferior vena cava wall. (5) Recurrent-free survival rate of the tumour. (6) Cancer-specific survival rate. (7) Overall survival rate. (8) Perioperative indicators including operation time, intraoperative bleeding volume and postoperative complications. SECONDARY ENDPOINTS: (1) The longest diameter of the tumour and (2) Lymph node condition.

MAIN INCLUSION CRITERIA

Patients with renal cell carcinoma and inferior vena cava tumour thrombus graded from Mayo II to IV and eligible for radical nephrectomy and inferior vena cava thrombectomy.

MAIN EXCLUSION CRITERIA

Patients with previous targeted therapy, chemotherapy or other interventions, or who cannot tolerate SABR or surgery.

PLANNED SAMPLE SIZE

20 patients.

ETHICS AND DISSEMINATION

The trial protocol and the informed consent of the subjects were submitted and approved by the Peking University Biomedical Ethics Committee.

TRIAL REGISTRATION NUMBER

ChiCTR1800015118.

Differential regulation of microRNA-15a by radiation affects angiogenesis and tumor growth via modulation of acid sphingomyelinase

Activation of acid sphingomyelinase (SMPD1) and the generation of ceramide is a critical regulator of apoptosis in response to cellular stress including radiation. Endothelial SMPD1 has been shown to regulate tumor responses to radiation therapy. We show here that the SMPD1 gene is regulated by a microRNA (miR), miR-15a, in endothelial cells (ECs). Standard low dose radiation (2 Gy) upregulates miR-15a and decreases SMPD1 levels. In contrast, high dose radiation (10 Gy and above) decreases miR-15a and increases SMPD1. Ectopic expression of miR-15a decreases both mRNA and protein levels of SMPD1. Mimicking the effects of high dose radiation with a miR-15a inhibitor decreases cell proliferation and increases active Caspase-3 & 7. Mechanistically, inhibition of miR-15a increases inflammatory cytokines, activates caspase-1 inflammasome and increases Gasdermin D, an effector of pyroptosis. Importantly, both systemic and vascular-targeted delivery of miR-15a inhibitor decreases angiogenesis and tumor growth in a CT26 murine colorectal carcinoma model. Taken together, our findings highlight a novel role for miR mediated regulation of SMPD1 during radiation responses and establish proof-of-concept that this pathway can be targeted with a miR inhibitor.

Effects of different doses of X-ray irradiation on cell apoptosis, cell cycle, DNA damage repair and glycolysis in HeLa cells

The present study examined the radiation biological response of cancer cells to different fractional irradiation doses and investigates the optimal fractional irradiation dose with improved biological effects. Radiobiological studies were performed at the molecular and cellular levels to provide insights into DNA damage and repair, and the apoptosis mechanism of cells that were exposed to different doses of X-ray irradiation (0, 2, 4, 6, 8, 10, 12.5, 15 and 20 Gy). Evidence of increased reactive oxygen species (ROS), DNA double strand breaks (DSB), cellular apoptosis, G2/M phase proportion and inhibition of cell proliferation were observed following irradiation. Differences in the ROS amount and apoptotic percentages of cells between the 2 and 4 Gy groups were insignificant. Compared with 0 Gy, the expression of the apoptosis suppression protein B-cell lymphoma-2 was decreased following at increased irradiation doses. However, apoptosis-associated protein Bcl-2-associated X (Bax), caspase-9 and BH3 interacting domain death agonist (Bid) were elevated following irradiation, compared with the control group (0 Gy). Furthermore, the expression levels of Bax in the 6, 8, 10 and 12.5 Gy groups were significantly increased, compared with the other groups. Caspase-9 expression with 2, 4, 6 and 8 Gy were increased compared with other groups, and the Bid levels with 6 and 8 Gy were also increased compared with other groups. G2/M phase arrest was associated with the increase of checkpoint kinase 1 and reduction of cyclin dependent kinase 1. DNA damage repair was associated with the protein Ku70 in the 2, 8, 10, 12.5, 15 and 20 Gy groups were less than other group. Compared with other group, Ku80 levels were reduced in the 6 and 8 Gy groups, and Rad51 levels were reduced in the 2, 8 and 10 Gy groups. The expression of hypoxia inducible factor-1α, c-Myc and glucose transporter 1 (GLUT1) demonstrated an increasing trend following irradiation in a dose-dependent manner, but the expression of pyruvate kinase M2, in the 2–10 Gy irradiation groups, and GLUT1, in the 12.5, 15 and 20 Gy irradiation groups, were reduced, compared with the other groups. Considering the DNA damage repair and apoptosis mechanisms at molecular and cellular levels, it was concluded that 2, 6, 8 and 10 Gy may be the optimal fractional dose that can promote cell apoptosis, and inhibit DNA damage repair and glycolysis.

Radiotherapy for renal cell carcinoma: renaissance of an overlooked approach

Conventional radiotherapy previously had a limited role in the definitive treatment of renal cell carcinoma (RCC), owing to the disappointing outcomes of several trials and the perceived radioresistance of this type of cancer. In this context, radiotherapy has been relegated largely to the palliation of symptoms in patients with metastatic disease, with variable rates of response. Following the availability of newer technologies that enable safe delivery of high-dose radiotherapy, stereotactic ablative radiotherapy (SABR) has become increasingly used in patients with RCC. Preclinical evidence demonstrates that RCC cells are sensitive to ablative doses of radiotherapy (≥8-10 Gy). Trials in the setting of intracranial and extracranial oligometastases, as well as primary RCC, have demonstrated excellent tumour control using this approach. Additionally, an awareness of the capacity of high-dose radiation to stimulate antitumour immunity has resulted in novel combinations of SABR with immunotherapies. Here we describe the historical application of conventional radiotherapy, the current biological understanding of the effects of radiation, and the clinical evidence supporting the use of ablative radiotherapy in RCC. We also explore emerging opportunities to combine systemic targeted agents or immunotherapies with radiation. Radiotherapy, although once an overlooked approach, is moving towards the forefront of RCC treatment.

Stereotactic spine radiosurgery: Review of safety and efficacy with respect to dose and fractionation

BACKGROUND

Stereotactic body radiotherapy (SBRT) is an emerging treatment option for spinal metastases with demonstrated efficacy in the upfront, postoperative, and re-treatment settings, as well as for tumor histologies considered radioresistant. Uncertainty exists regarding the optimal dose and fractionation schedule, with single and multifraction regimens commonly utilized.

METHODS

A literature search of the PubMed and Medline databases was conducted to identify papers specific to spine SBRT and the effect of varying dose/fractionation regimens on outcomes. Bibliographies of relevant papers were searched for further references, and international spine SBRT experts were consulted.

RESULTS

Local control rates generally exceed 80% at 1 year, while high rates of pain control have been attained. There is insufficient evidence to suggest superiority of either single or multiple fraction regimens with respect to local control and pain control. Low rates of toxicity have been reported, assuming strict dose constraints are respected. Radiation myelopathy may be the most morbid toxicity, although the rates are low. The risk of vertebral compression fracture appears to be associated with higher doses per fraction such as those used in single-fraction regimens. The Spinal Instability Neoplastic Score should be considered when evaluating patients for spine SBRT, and prophylactic stabilisation may be warranted. Pain flare is a relatively common toxicity which may be mediated with prophylactic dexamethasone. Because of the treatment complexity and potentially serious toxicities, strict quality assurance should occur at the organizational, planning, dosimetric, and treatment delivery levels.

CONCLUSION

Both single and multifraction regimens are safe and efficacious in spine SBRT for spinal metastases. There may be advantages to hypofractionated treatment over single-fraction regimens with respect to toxicity. Ongoing investigation is underway to define optimal dose and fractionation schedules.

Stereotactic Body Radiation Therapy for Stage I Non-Small Cell Lung Cancer

Stereotactic body radiation therapy (SBRT) has had a profound impact on the treatment paradigm for medically inoperable patients with stage I non-small cell lung cancer. Local control and survival outcomes from prospective collaborative trials using SBRT have been highly favorable in this challenging patient population. Further study in medically operable patients is ongoing; however, randomized trials to help answer this question have terminated early because of poor accrual. Available prospective and retrospective data are discussed for the use of SBRT with regard to the medically inoperable and operable patient populations, as well as considerations for fractionation, dose, and toxicity.