Timing And Prognosis Of Thoracic Radiotherapy For Limited Disease Small Cell Lung Cancer

Objective: To explore the timing of thoracic radiotherapy intervention in the treatment of limited disease small cell lung cancer,and analyze re l-ated prognostic factors.Methods: The clinical data of 53 patients with limited disease small cell lung cancer who were treated with 3D-CRT or IMRT after induction chemotherapy at the Affiliated Tumor Hospital of Guangxi Medical Univer-sity from January 1,2009 to October 31,2018 were collected and reviewed.They all had complete medical records and follow-up data.The data was statistically analyzed by SPSS 24.0 software.Survival rates were cal-culated by Kaplan-Meier analysis.Comparing survival differences between different groups was analyzed by Log-rank.The prognosis was analyzed by Cox proportional hazard model.Results: The median overall survival time(MST)was 20.0 months;the 1-year and 2-year overall survival(OS)rates were 80.3% and 38.7%, respectively.The median progression-free survival(PFS)time was 12.0months;the 1-year and 2-year PFS were 49.6% and 20.7%,respectively.The median OS of patients in the early intervention radiotherapy group was 23.0 months,while the median OS of patients in the late intervention radiotherapy was 19.0 months(P=0.012).The median PFS of the two gr-oups of patients was 13.0 months and 12.0 months,respectively(P=0.748).After the patient underwent thoracic radiotherapy,the incidence of leukopenia above grade 3 in the early intervention radiotherapy group was si-gnificantly higher than that in the late intervention radiotherapy group(P=0.016).In terms of radiation pneumonitis,the probability of early interve-ntion radiotherapy patients with above grade 3 radiation pneumonia was4.5%,which was lower than 19.4% of the late intervention radiotherapy g-roup,but the difference between the two groups was not statistically significant(P=0.143).There was no significant difference in the incidence of radiation esophagitis,thrombocytopenia and hemoglobin reduction in the t-wo groups.Univariate analysis showed that the group of the early interv e-ntion radiotherapy had better survival than the group of that the late int e-rvention radiotherapy(P=0.012),while the patients with non-prophylactic c-ranial irradiation were in poor survival.(P=0.009).Combine with multiv a-riate analysis,received Early interventional thoracic radiotherapy(P=0.045)and prophylactic cranial irradiation(P=0.036)were independent prognos ti-c factors for overall survival in limited disease small cell lung cancer p atients.The Gross target volume high dose group had better Locoregional recurrence free survival and Distant metastasis-free survival than the low i-rradiation group(P<0.05).Conclusion: Early intervention in thoracic radiotherapy can bring surv-ival benefits to patients with limited disease small cell lung cancer(withi-n 3 cycles of induction chemotherapy)Prophylactic cranial irradiation is an influential factor for the prognosis of limited disease small cell lung cancer.Gross target volume irradiation dose>60Gy may improve locoregion-al recurrence free survival and distant metastasis-free survival.