Re-Irradiation of Lung Lesions by Stereotactic Ablative Radiotherapy

Purpose/Objective(s)

Patients with primary lung cancer or other primary cancers have a high risk of loco-regional recurrence or pulmonary metastases requiring thoracic re-irradiation. Only very limited data about lung re-irradiation exist. Stereotactic Ablative Radiotherapy (SABR) was used in various clinical situations and several attempts have been made to apply SABR to lung lesions previously irradiated. Nevertheless, the use of high dose in the re-irradiation is not without risks. Aim of this study is to evaluate the outcomes of re-irradiation by SABR in terms of Local Control (LC), Progression Free Survival (PFS) and Overall Survival (OS) and to assess the toxicities and predictive factor of response.

Materials/Methods

From April 2011 to April 2021, 43 patients received a re-irradiation by SABR in the lung on 58 lesions. Primary cancer was lung in 72%, colon-rectal in 14%, and 14% others. Thirty-four lesions were retreated in the same lobe, 14 in the adjacent lobe, 10 in the contra-lateral lung. Four lesions had a central localization, 54 lesions had a peripheral location. The medium volume was 33.4cc (range: 0.9-260.8cc). The medium BED(10) of first treatment was 103.1 Gy (range: 39-151.2 Gy). The medium BED(10) of re irradiation by SABR was 95.34 Gy (range: 39-151.2 Gy). Thirteen lesions received 1 fraction, 45 multiple fractions (range:3-10 fractions). The schedules most represented for re-irradiation were 30 Gy in 1 fraction, 45 Gy in 3 fractions and 54 Gy in 3 fractions.

Results

Rates of LC at 1, and 3 years were 51% and 43%, respectively. Rates of PFS at 1, and 3 years were 38% and 21% respectively. The median OS was 32 months (range: 3–131 months), Rates of OSat 1, and 3 years were 77% and 43%. In the univariate analysis the single fraction vs. multiple fractions, and the volume (<33.4 cc) showed a statistically significant correlation with LC (P= 0,0032 and P=0,0008, respectively) and PFS (P= 0,0080 and P=0,0258). In the univariate analysis, the single fraction vs. multiple fractions showed a statistically significant correlation also with OS (P = 0,0014). In terms of acute toxicity, 26% side effects were observed, 7 cases Grade 1 (in the form of dyspnea, cough and dysphagia) and 8 cases Grade 2 (in the form of dyspnea, cough, brachial plexopathy, pain and esophageal hemorrhage). In terms of late toxicity 39% side effects were observed, 11 cases Grade 1 (in the form of dyspnea, atelectasis, fibrosis, rib fracture, pain and asthenia), 10 cases Grade 2 (in the form of dyspnea, gastro-esophageal reflux, soft tissue necrosis, pulmonary fibrosis, pleural effusion and asthenia) and 2 cases Grade 3 occurring in the form of pain and dyspnea.

Conclusion

SABR re-irradiation can play a role in prolonging survival in lung recurrence with an acceptable toxicity. However, more knowledge is necessary to mitigate the risk of severe toxicity.