Abstract:

Most patients with stage Ⅲ NSCLC are not suitable for surgery because of tumor extension or comorbidities. The absence of loco⁃regional control，predominantly observed within the primary lesion，remains a major cause of treatment failure after radiotherapy for locally unresectable advanced NSCLC. For patients with NSCLC，the tumor control rate increases with the biological effect dose（BED）delivered to the primary tumor. Patients receiving 30 Gy in a single fraction（120 Gy BED）have a local control（LC）rate of 98%. Another dose⁃ response analysis showed that favorable outcomes plateaued around 120 Gy BED. High⁃dose⁃rate（HDR）brachy⁃ therapy can deliver high radiation doses in a single fraction to the target tumor. The dose falls rapidly，maintaining a virtually low dose irradiated to OARs. Moreover，HDR brachytherapy inhibits the accelerated re⁃proliferation oftumor cells，leads to lethal tumor cell damage，and eradicates target deviation attributed to organ movement or setup uncertainties，consequently avoiding unnecessary irradiation to OARs. In the current era of immunotherapy，thoracic radiation has become even more important for ensuring long⁃term survival in patients with NSCLC. Combination of HDR brachytherapy with immunotherapy may lead to better survival. We observed favorable clinical survival and low rates of acute and late toxicities，providing a new treatment strategy for locally advanced NSCLC.

Key words:

high?dose?rate brachytherapy, intensity?modulated radiation therapy, lymph nodes, non? small cell lung cancer