The impact of a mono-institutional experience in lung metastases treated with stereotactic body radiation therapy (SBRT): a retrospective analysis

Background: Stereotactic body radiation therapy (SBRT) can deliver a very high dose to the tumor while minimizing the damage to the surrounding structures. The purpose of our study was to investigate local control (LC), local progression-free survival (LPFS), and overall survival (OS) to determine the impact of SBRT lung treatment in metastatic lesions. A secondary end point estimated the impact of colorectal metastases stratified for the same parameters. Methods: A total of 265 patients with, in total, 483 lesions were analyzed: 34% of patients had a diagnosis of primary non-small cell lung cancer (NSCLC) compared with 66% with lung metastases. Considering only the metastatic lung tumors, 37% of the patients presented localized colorectal metastases. Follow-up was generally undertaken at 4 weeks, and 2, 4, 6, 12 months following SBRT, and annually thereafter. Toxicities were scored according to the Common Terminology Criteria for Adverse Events definitions. Results: In our sample, LC rates at 1, 3, and 5 years were, respectively, 80%, 58%, and 44%, (median LC was 44 months), LPFS was 65%, 41%, and 36% (median LPFS was 36 months), and OS was respectively 85%, 69%, and 56% (median OS was 64 months). All patients finished their SBRT course without interruptions related to acute toxicity. No acute or late Grade 3 or higher pulmonary fibrosis was founded. Acute and late Grade 2 toxicities were 2.5%. Histology shows statistical differences in LC (P<0.01). SBRT stratified by primary tumor, excluding lung lesions from primary colorectal tumor cases, shows increased LC rates at 1, 3, and 5 years, respectively 83%, 72% and 70%. Median LC was 56 months (P<0.01). Conclusions: SBRT in lung lesions showed efficacy in both responses and maintenance. No significant toxicity was found, while good patient compliance was observed. No variables except histology showed significant differences. We observed that for patients with primary tumor metastases from the gastrointestinal region, who have undergone previous pulmonary chemotherapy treatments (2 years), there are lower response rates than the rest of the examined sample. The study suggests that SBRT treatment of lung lesions may achieve a better result if performed earlier than in other therapeutic approaches.