Application and Progress of Functional Lung Avoidance Radiotherapy for Lung Cancer

Lung cancer is a major disease that seriously threatens human life and health. As one of the main treatment methods for lung cancer, radiotherapy (RT), while combating cancer cells, inevitably causes damage to the surrounding normal lung tissues. Radiation-induced lung injury (RILI) is a common and serious complication of RT that can seriously affect the treatment process of patients, reducing their quality of life (QOL) and survival time. Conventional RT aims to reduce the incidence of RILI in patients by limiting the radiation dose to normal lung tissue. This approach assumes that lung function is uniformly distributed. However, there is heterogeneity in human lung function. To address this challenge, functional lung imaging (FLI) has emerged and become a research focus. In the field of medical imaging technology, Single-Photon Emission Computed Tomography (SPECT), Positron Emission Tomography (PET), Magnetic Resonance Imaging (MRI), CT, and other technologies can all obtain FLI. Whatever imaging modality is used, lung perfusion (Q) on imaging serves as a surrogate for RILI. Furthermore, the combination of FLI and RT has given rise to functional lung avoidance RT (FLART), which can precisely reduce radiation exposure to functional lung (FL) regions by adjusting the radiation dose distribution, thereby effectively reducing the incidence of RILI. This narrative review comprehensively explores several key aspects, including FLI modalities, the definition of FL, the clinical applications of FLART, the impact of FLART on QOL, and the limitations of FLART. These discussions provide a good basis and guidance for the follow-up clinical work.