Clinical outcomes and toxicity predictors of thoracic re-irradiation for locoregionally recurrent lung cancer. (May 2020) - Yang, Wen-Chi
Highlights: The role of thoracic control for lung cancer has become increasingly important with improvements in lung cancer treatment and patient survival. Thoracic re-irradiation became feasible with the advance and adaptation of radiation technology. Our study retrospectively collected data related to clinicopathological features and treatment outcomes of 50 patients who had two courses of thoracic RT in at least 50% overlapping fields. A promissing local control with median time to local progression of 18 months and a median overall survival of 25.1 months were found. We also found that subsequent chemotherapy with taxanes- or gemcitabine-based regimen following thoracic re-irradiation was significantly related to lethal lung events. These results helped prove the feasibility of re-irradiation with conventionally fractionated RT and increase awareness regarding underestimated lung toxicity resulting from subsequent chemotherapy following thoracic re-irradiation. Abstract: Background and purpose: Thoracic re-irradiation may be an alternative treatment for lung cancer patients who develop intrathoracic locoregional recurrence without systemic progression. This study aimed to retrospectively assess locoregional control, clinical outcomes, and toxicities in lung cancer patients who received thoracic re-irradiation. Materials and methods: We retrospectively reviewed 50 lung cancer patients who received thoracic re-irradiation using conventional photon radiotherapy (RT) and stereotactic body radiotherapy (SBRT) between 2009 and 2017. The correlations of clinicopathologic factors, treatment factors, and dosimetric factors of RT with time to local progression (TTLP), progression-free survival (PFS), and overall survival (OS) after starting thoracic re-irradiation were calculated using log-rank tests and Cox regression models. Results: The median re-irradiation dose in equivalent dose in 2-Gy fractions was 51.1 Gy, and the mean re-irradiation planning target volume was 201.58 ml. The median mean lung dose (MLD) was 4.18 Gy, and the total lung volumes receiving a dose of 5 Gy (lung V5) and of 20 Gy (V20) were 19.8% and 5.85%, respectively. The TTLP, PFS, and OS were 18.0, 5.9, and 25.1 months, respectively. Lung V5 ( p < 0.001), V20 ( p = 0.011), and MLD ( p = 0.002) were significantly associated with grade ≥2 lung toxicity. Seven (14%) patients developed lethal lung events. Subsequent chemotherapy following thoracic re-irradiation was significantly correlated with lethal lung events ( p = 0.009). Conclusion: Promising local control can be achieved with thoracic re-irradiation in lung cancer patients with locoregional recurrence. However, unexpected lethal lung events may occur, especially in patients receiving systemic therapy following thoracic re-irradiation.