Distant Metastasis Patterns And Abscopal Effects Of Non-small Cell Lung Cancer

Background:The prognosis of non-small cell lung cancer(NSCLC)patients is dismal,especially those with metastatic disease.However,there are few studies that have systematically explored the incidence rate and prognostic value of patterns of different distant metastasis in NSCLC patients.This study aimed to explore the patterns and prognosis differences of site-specific metastasis in NSCLC patients by a large population-based database,which was vital for the reasonable classification of advanced NSCLC patients and could provide the basis for individualized precise treatment.The proportion of distant metastasis in NSCLC is high(about 57%).Drug therapy is the main treatment for advanced NSCLC,but the efficacy of traditional chemotherapy is limited.The median survival time is only 8-10 months,and the 1-year survival rate is only about 40%.Radiotherapy plays an important role in the treatment of patients with advanced NSCLC,and about 60%-70% patients with NSCLC have received radiotherapy during the course of the disease.With the development of radiotherapy technology and the application of radiation-integrated therapy,high-dose radiotherapy(HDRT)plays an increasingly important role in cancer therapy.Studies have shown that HDRT can lead to direct tumor cells death,promote tumor necrosis and antigen release.It could activate the immune system in a form of in situ tumor vaccine and transform the tumor microenvironment from an immune desert state to an inflamed-immune infiltrated state,which leads to strong anti-tumor immunity.Abscopal effects could be observed even in a very small number of patients.In this process,its original local therapeutic function showed systemic anti-tumor effects.With the advent of immunotherapy,especially the application of immune checkpoint inhibitors,a breakthrough of the abscopal effects of HDRT is not far on the road.However,the mechanism of the abscopal effects is still unclear.Therefore,the intensive study of the immune effect and regulation mechanism of the abscopal effects will help to promote its universalization,which has important theoretical significance and clinical prospects.Therefore,the establishment of the abscopal effects animal model can provide an experimental platform for the in-depth study of the mechanism of the phenomenon.It is conducive to the exploration of the molecular mechanism and universalization of the abscopal effects,which has important theoretical significance and clinical prospects.Methods:1.Patients diagnosed with NSCLC between 2010 and 2014 were collected from the Surveillance,Epidemiology,and End Results(SEER)database.Survival comparisons were achieved by Kaplan-Meier methods and log-rank tests.Cox proportional hazard model were performed to determine the factors related to improved overall survival(OS)and cancer-specific survival(CSS).2.Lewis cells were inoculated to the bilateral thighs of C57 mice to construct a model with transplanted and metastatic lung tumor.The right thigh of the mice received HDRT.PD-L1 antibody was injected intraperitoneally.The tumor volume growth curve was observed and plotted.Survival comparison was achieved by Kaplan-Meier method and log-rank test.Flow cytometry was used to analyze the changes of CD8+ T cells,CD4+ T cells,MDSCs,DCs and Tregs in orthotopic and distant lesions.Results:1.From SEER database,we finally identified 108,464 NSCLC patients diagnosed from 2010 to 2014.Among the identified group,51,788 patients(47.7%)had DM at diagnosis.Patients with the characteristics of male,black race,higher clinical T stage,positive nodes,higher tumor grade,or adenocarcinoma were more likely to have metastasis.For NSCLC patients,the most common single metastatic site was bone,and the least common was liver.As for multi-site metastases,bone and lung was the most common two-site metastasis,and bone,liver and lung was the most common three-site metastasis.As for NSCLC subtypes,the results showed that the most common single metastatic site was bone for the patients with adenocarcinoma(AD)and adenosquamous carcinoma(ASC),with the percentage of 36.13% and 42.08%,respectively.As for the patients with squamous cell carcinoma(SQCC)and other subtypes,single lung metastasis was the most common,with the percentage of 37.68% and 43.09%,respectively.Interestingly,the most common single metastatic site in patients with large cell carcinoma(LCC)was brain,accounting for 37.57%.The most common two-site metastasis was bone and lung,with the percentage of 28.79% in patients with AD,28.51% in patients with SQCC,27.37% in patients with ASC,and 24.29% in patients with other subtypes,respectively.However,the most common two-site metastasis was bone and liver for LCC patients,accounted for 26.42%.Considering three-site metastasis,bone,liver and lung was the most common combination for all subtypes,with the percentage of 30.77%(AD),38.85%(SQCC),31.94%(ASC),34.86%(LCC),and 37.93%(other subtypes),respectively.An isolated liver metastasis had the worst OS and CSS among single metastasis.Furthermore,for patients with multi-site metastasis,OS and CSS were the worst if liver metastasis occurred.2.Compared with the control,only HDRT,and only PD-L1 antibody groups,HDRT combined with PD-L1 antibody significantly inhibited the growth of orthotopic tumors(P < 0.05),and the growth rate of distant tumors was also significantly inhibited(P < 0.05).Besides,the survival time of the mice in the group with combined treatment was significantly longer than that in the other three groups(P < 0.05).Flow cytometry analysis of immune changes showed that the infiltration of CD4+ T cells and CD8+ T cells of combined treatment group significantly increased in orthotopic and distant lesions(P < 0.05).DCs infiltration was also increased in orthotopic tumors of the combined treatment group(P < 0.05).For immunosuppressive cells,MDSCs infiltration in distant lesions was reduced in the group with combined treatment and HDRT group(P < 0.05).At the same time,the infiltration of Tregs in orthotopic and distant lesions in the group with combined treatment was significantly lower than that in the control group(P < 0.05).Conclusions:1.Our study demonstrated that in NSCLC patients,bone was the most commonly targeted site,both for single-or multi-site metastasis.As for the subtypes of NSCLC,LCC had more specific metastatic features.The most common single metastatic site was brain for LCC patients,and the most common two-site metastasis combination was bone and liver.Importantly,we found that metastasis to the liver alone or in combination with other organs was the worst prognosis factor for metastatic NSCLC patients,while isolated lung metastasis had the best outcomes.2.HDRT combined with PD-L1 antibody therapy could successfully induce the abscopal effects,which showed that the growth of orthotopic and distant tumors was significantly inhibited.The survival time of the group with combined treatment was also significantly prolonged.Analysis of the changes of immune microenvironment suggested that combined therapy could effectively improve and enhance the immune status in the orthotopic and distant lesions,which was manifested as increased immune effector cells infiltration and reduced immunosuppressive cells infiltration.Finally,both orthotopic and distant lesions showed strong anti-tumor immunity.