Stereotactic body radiation therapy as a derivative of stereotactic radiosurgery: clinically independent but with enduring common themes

Vascular damage in tumors: a key player in stereotactic radiation therapy?

The use of stereotactic radiation therapy (SRT) for cancer treatment has grown in recent years, showing excellent results for some tumors. The greatly increased doses per fraction in SRT compared to conventional radiotherapy suggest a 'new biology' that determines treatment outcome. Proposed mechanisms include significant damage to tumor blood vessels and enhanced antitumor immune responses, which are also vasculature-dependent. These ideas are mostly based on the results of radiation studies in animal models because direct observations in humans are limited. However, even preclinical findings are somewhat incomplete and result in ambiguous conclusions. Current evidence of vasculature-related mechanisms of SRT is reviewed. Understanding them could result in better optimization of SRT alone or in combination with immune or other cancer therapies.

Stereotactic Body Radiotherapy for Oligometastasis: Opportunities for Biology to Guide Clinical Management

Oligometastasis refers to a state of limited metastatic disease burden, in which surgical or ablative treatment to all known visible metastases holds promise to extend survival or even effect cure. Stereotactic body radiotherapy is a form of radiation treatment capable of delivering a high biologically effective dose of radiation in a highly conformal manner, with a favorable toxicity profile. Enthusiasm for oligometastasis ablation, however, should be counterbalanced against the limited supporting evidence. It remains unknown to what extent (if any) ablation influences survival or quality of life. Rising clinical equipoise necessitates the completion of randomized controlled trials to assess this, several of which are underway. However, a lack of clear identification criteria or biomarkers to define the oligometastatic state hampers optimal patient selection.This narrative review explores the evolutionary origins of oligometastasis, the steps of the metastatic process at which oligometastases may arise, and the biomolecular mediators of this state. It discusses clinical outcomes with treatment of oligometastases, ongoing trials, and areas of basic and translational research that may lead to novel biomarkers. These efforts should provide a clearer, biomolecular definition of oligometastatic disease and aid in the accurate selection of patients for ablative therapies.

Role of HIF-1α in response of tumors to a combination of hyperthermia and radiation in vivo

PURPOSE

Mild temperature hyperthermia (MTH) increases blood flow and oxygenation in tumours. On the other hand, high-dose-per-fraction irradiation damages blood vessels, decreases blood flow and increases hypoxia in tumours. The radiation-induced hypoxia in tumours activates hypoxia-inducible factor-1α (HIF-1α) and its target genes, such as vascular endothelial growth factor (VEGF), promoting revascularization and recurrence. In the present study, we examined the hypothesis that MTH inhibits radiation-induced upregulation of HIF-1α and its target genes by increasing tumour oxygenation.

MATERIALS AND METHODS

FSaII fibrosarcoma tumours grown subcutaneously in the legs of C3H mice were used. Tumours were irradiated with 15 Gy using a ⁶⁰Co irradiator or heated at 41 °C for 30 min using an Oncothermia heating unit. Blood perfusion and hypoxia in tumours were assessed with Hoechst 33342 and pimonidazole staining, respectively. Expression levels of HIF-1α and VEGF were determined using immunohistochemical techniques. Apoptosis of tumour cells was quantitated via TUNEL staining and the effects of treatments on tumour growth rate were assessed by measuring tumour diameters.

RESULTS

Irradiation of FSaII tumours with a single dose of 15 Gy led to significantly decreased blood perfusion, increased hypoxia and upregulation of HIF-1α and VEGF. On the other hand, MTH at 41 °C for 30 min increased blood perfusion and tumour oxygenation, thereby suppressing radiation-induced HIF-1α and VEGF in tumours, leading to enhanced apoptosis of tumour cells and tumour growth delay.

CONCLUSION

MTH enhances the anti-tumour effect of high-dose irradiation, at least partly by inhibiting radiation-induced upregulation of HIF-1α.

Radiation Oncology Physician Practice in the Modern Era: A Statewide Analysis of Medicare Reimbursement

Introduction

In recent years, major changes in health care policy have affected oncology practice dramatically. In this context, we examined the effect of practice structure on volume and payments for radiation oncology services using the 2013 Medicare Provider Utilization and Payment Data: Physician and Other Supplier Public Use File (POSPUF) for New York State radiation oncologists.

Methods

The Medicare POSPUF data was queried, and individual physicians were classified into freestanding office-based and hospital-based practices. Freestanding practices were further subdivided into urology, hematology-oncology, and other ownership structures. Additional variables analyzed included gender, year of medical school graduation, and Herfindahl-Hirschman Index (HHI). Statistical analyses were performed to assess the impact of the above-mentioned variables on reimbursements.

Results

There were 236 New York State radiation oncologists identified in the 2013 Medicare POSPUF dataset, with a total reimbursement of $91,525,855. Among freestanding centers, the mean global Medicare reimbursement was $832,974. Global Medicare reimbursement was $1,328,743 for urology practices, compared to $754,567 for hematology-oncology practices and $691,821 for other ownership structures (p < 0.05). The mean volume of on-treatment visits (OTVs) was 240.5 per year, varying by practice structure. The mean annual OTV volumes for urology practices, hematology-oncology practices, other freestanding practices, and hospital-based programs were 424.6, 311.5, 247.5, and 209.3, respectively. After correcting for gender, physician experience, and HHI, practice structure was predictive of freestanding reimbursement and on treatment visit volume.

Conclusion

Higher Medicare payment was significantly predicted by the type of practice structure, with urology-based and hematology-oncology practices accounting for the highest total reimbursement and OTV volume.

[Current Status of Stereotactic Ablative Radiotherapy (SABR) for Early-stage Non-small Cell Lung Cancer]

目前比较立体定向消融放疗（stereotactic ablative radiotherapy, SABR）与手术治疗早期非小细胞肺癌（non-small cell lung cancer, NSCLC）的随机研究证据尚不多，高水平的循证医学证据更是缺乏。尽管STARS和ROSEL两项随机研究结果荟萃分析显示SABR较手术耐受性更好，生存不劣于手术，但是目前仍仅推荐拒绝手术或不可手术的早期NSCLC首选SABR，期待着正在进行的随机研究VALOR（Veterans Affairs Lung Cancer Surgery or Stereotactic Radiotherapy in the US）和SABRTooth（SABRTooth study in the United Kingdom）的结果。许多回顾性的研究和病例对照研究显示了SABR治疗的安全性和有效性（局部控制率达90%以上，5年生存率达70%），但是由于肿瘤分期定义、如何决定可否手术及手术患者采用手术方式（开胸或胸腔镜辅助）等不同，很难比较SABR和手术的优劣，尽管大部分结论是两种方法疗效相似，但难以成为循证医学证据，因此争论热点是哪一种方法更安全、创伤更小。本文将就以上争论热点进行述评。

Emerging Treatment Paradigms in Radiation Oncology

Rapid advancements in radiotherapy and molecularly targeted therapies have resulted in the development of potential paradigm-shifting use of radiotherapy in the treatment of cancer. In this review, we discuss some of the most promising therapeutic approaches in the field of radiation oncology. These strategies include the use of highly targeted stereotactic radiotherapy and particle therapy as well as combining radiotherapy with agents that modulate the DNA damage response, augment the immune response, or protect normal tissues.