Survival And Prognosis Analysis Of Modern Radiation Therapy In Completely Resected Thymoma

Objectives To investigate the role of postoperative radiotherapy under modern radiotherapy techniques in Masaoka-Koga stage Ⅱ and Ⅲ thymoma after complete resection.Methods From January 2000 to December 2017,patients with Masaoka-Koga stage Ⅱand Ⅲ thymoma who underwent complete resection with or without modern technique radiotherapy were included and analyzed.Clinical,pathological,therapeutic and follow-up information was collected.A total of 244 patients met the selection criteria,and 51(20.9%)had myasthenia gravis.172(70.5%)patients with stage Ⅱ thymoma,72 patients(29.5%)with stage Ⅲ.Of these,102(41.9%)were surgery alone,142(58.1%)were treated with postoperative radiotherapy(PORT).A total of 6 patients(2.5%)received chemotherapy,and 2(1.4%)were treated with both radiotherapy and chemotherapy.The Kaplan-Meier method was used to analyze overall survival(OS),disease-specific survival(DSS),disease-free survival(DFS)and local recurrence free survival(LRFS),and a multivariate Cox model was created to identify factors associated with OS and DSS.Results The median follow-up was 76 months,the 5-year and 10-year OS was 93.8%,83.6%and 95.4%,86.9%in the surgery and PORT groups(p=0.34),while the DSS was 93.8%,86.3%and 99.0%,93.9%(p=0.038),with no significant difference on DFS of 85.0%,75.9%and 76.9%,65.5%(p=0.65),respectively.Subgroup analysis showed that stage Ⅲ patients had OS and DSS benefited from PORT,with 5-year and 10-year OS of 95.8%and 81.4%in the PORT group and 83.0%and 54.4%in the surgery alone group,respectively(p=0.038);5-year and 10-year DSS of 97.6%and 91.8%in the PORT group and 83.0%and 54.4%in the surgery alone group,respectively(p=0.002).There was a significant benefit in LRFS for PORT(p=0.048),especially for stage Ⅱb(p=0.045)and stage Ⅲ(p=0.021).The failure pattern of local,regional and distant were similar in the surgery alone group,50.1%,56.4%and 50.1%,respectively,with regional and distant dominating the PORT group(64.6%and 74.3%).The pleura was the most common site of regional metastasis at 82.8%and the lung the most common site of distant metastasis at 65.4%.On multivariate analysis,stage Ⅲ and type B2/B3 were associated with poorer OS,stage Ⅱ and PORT were associated with better DSS.Conclusions Postoperative radiotherapy with modern techniques for complete resection thymoma improves not only local control of tumor but also DSS,although no significant benefit has been seen for OS.The benefits are more pronounced in stage Ⅲ,with benefits in both DSS and OS.Regional and distant failure is a major pattern of.postoperative radiotherapy failure,and whether systemic therapy(e.g.,stage Ⅲ)needs to be further explored.It is recommended that postoperative radiotherapy be given after complete resection of stage Ⅲ thymoma and that stage Ⅱb be given selectively for adverse factors such as pathological type B2/B3,and the irradiation field cover the tumor bed only.Look forward to the final results of the multicenter randomized controlled trials that have been carried out.