Local ablative radiotherapy for oligometastatic non-small cell lung cancer

In metastatic non-small cell lung cancer (NSCLC), the role of radiotherapy (RT) has been limited to palliation to alleviate the symptoms. However, with the development of advanced RT techniques, recent advances in immuno-oncology therapy targeting programmed death 1 (PD-1) and programmed death ligand 1 (PD-L1) and targeted agents for epidermal growth factor receptor (EGFR) mutation or anaplastic lymphoma kinase (ALK) translocation allowed new roles of RT in these patients. Within this metastatic population, there is a subset of patients with a limited number of sites of metastatic disease, termed as oligometastasis that can achieve long-term survival from aggressive local management. There is no consensus on the definition of oligometastasis; however, most clinical trials define oligometastasis as having 3 to 5 metastatic lesions. Recent phase II randomized clinical trials have shown that ablative RT, including stereotactic ablative body radiotherapy (SABR) and hypofractionated RT, to primary and metastatic sites improved progression-free survival (PFS) and overall survival (OS) in patients with oligometastatic NSCLC. The PEMBRO-RT study, a randomized phase II study comparing SABR prior to pembrolizumab therapy and pembrolizumab therapy alone, revealed that the addition of SABR improved the overall response, PFS, and OS in patients with advanced NSCLC. The efficacy of RT in oligometastatic lung cancer has only been studied in phase II studies; therefore, large-scale phase III studies are needed to confirm the benefit of local ablative RT in patients with oligometastatic NSCLC. Local intensified RT to primary and metastatic lesions is expected to become an important treatment paradigm in the near future in patients with metastatic lung cancer.

Review of tumor radiosensitivity from the point of view of stereotactic ablative radiotherapy / 中华放射医学与防护杂志

With the technical advances, radiotherapy has ushered in a new era of 3-D and 4D, which are associated with significantly improved therapy precision and profound change in fractionation pattern. The radiotherapy with focused rays, represented by both 3D-conformal radiotherapy (3D-CRT) and intensity modulated radiation therapy ( IMRT ) , involves the delivery of high doses to the target volume, with a less attendant potential for damages to surrounding normal tissue. Radiotherapy has been able to deliver precise, efficient, low toxic access to therapeutic effects thanks to the advance in image-guided techniques, the combination of radiotherapy equipment with image-guided system, the availability of target position information before radiotherapy with 3D or 4D image modality, the stereotactic body radiation therapy (SBRT)/the stereotactic ablation radiosurgery (SABR). Conventional fractionated radiation has seen the therapeutic effect of convincing and promising. The conventional theory of radiobiology, which deems the tumor not sensitive to radiotherapy to have good reaction with SABR, has been unable to explain the mechanism of antitumor effects arising from such exposure modes. Therefore, it is now urgent to create new radiobiological theory and system for radiotherapy in order to better illustrate the principle and mechanism of new technologies, to establish its internal relation with conventional radiobiology and to lay theoretical groundwork for popularization and dissemination of SABR in clinical medicine.