Incorporating functional lung imaging (FLI) into radiation therapy planning in patients with lung cancer: A systematic review and meta-analysis

Abstract

Purpose

To provide an understanding of current FLI techniques, and their potential to improve dosimetry and outcomes for lung cancer patients receiving radiation therapy (RT).

Methods

EMBASE, PubMed, and Cochrane Library were searched from 1990 until April 2023. Articles were included if they reported on FLI in one of: techniques, incorporation into RT planning for lung cancer, quantification of RT-related outcomes for lung cancer patients. Studies involving all RT modalities, including stereotactic body radiotherapy and particle therapy, were included. Meta-analyses were conducted to investigate differences in dose-function parameters between anatomical and functional RT planning techniques, as well as to investigate correlations of dose-function parameters with grade 2+ radiation pneumonitis (RP).

Results

178 studies were included in the narrative synthesis. We report on FLI modalities, dose-response quantification, functional lung (FL) definitions, FL avoidance techniques, and correlations between FL irradiation and toxicity. Meta-analysis results show that FL avoidance planning gives statistically significant absolute reductions of 3.22% to the fraction of well-ventilated lung receiving 20 Gy or more (vent-fV20), 3.52% to the fraction of well-perfused lung receiving 20 Gy or more (perf-fV20), 1.3 Gy to the mean dose to the well-ventilated lung (vent-fMLD), and 2.41 Gy to the mean dose to the well-perfused lung (perf-fMLD). Increases in the threshold value for defining FL are associated with decreases in functional parameters. For intensity-modulated radiation therapy and volumetric modulated arc therapy, avoidance planning results in a 13% rate of grade 2+ RP, which seems reduced compared to results from conventional planning cohorts. A trend of increased predictive ability for grade 2+ RP was seen in models using FL information, but was not statistically significant.

Conclusions

FLI shows promise as a method to spare FL during thoracic RT, but interventional trials related to FL avoidance planning are sparse. Such trials are critical to understanding the impact of FL avoidance planning on toxicity reduction and patient outcomes.