2192 - Conditional Survival and Hazard Rates of Patients with LS-SCLC Underwent IMRT in the First-Line Chemoradiotherapy Era: Influence of Prognostics Factors over Time

T. Zhan¹, W. Wang¹, L. Deng¹, T. Zhang¹, X. Wang¹, J. Wang², W. Liu Jr¹, F. Qinfu¹, Y. Zhai³, J. LV¹, Z. Xiao³, N. Bi¹, Z. Zhou³, and Y. X. Li³; ¹Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China, ²Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China, ³Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China

Purpose/Objective(s): We aim to evaluate dynamic survival of limited-stage small cell lung cancer (LS-SCLC) treated with intensity-modulate radiation therapy (IMRT) in the first-line chemoradiotherapy (CRT) era. Materials/

Methods: This retrospective cohort study reviewed 821 LS-SCLC patients who underwent chemoradiotherapy with IMRT. Conditional survival and annual hazard rates were used to evaluate the dynamic survival. The clinical prognostic factors were estimated by Cox regression proportional analysis. The corresponding conditional survival of each factor was calculated, with IPTW used to balance other confounding factors. The differences of conditional survival were evaluated by standardized differences (D value). Sensitivity analysis was also conducted.
Results: The median follow-up of the entire cohort was 66 months (95% CI:62.20-69.80). 3-year survival rates raised from 45.47% (95%CI: 42.1%-48.9%) at diagnosis to 93.01% (95%CI: 88.4%-97.7%) at year five for conditional overall survival and from 30.31% (95%CI: 27.2%-33.5%) to 90.71% (95%CI:83.9%-97.5%) at year five for conditional progression-free survival. The annual hazard rates for patients reach the highest point between year 1 to year 2 for death and drop continuously for progression. Supraclavicular metastasis, smoking history, sequence of chemoradiotherapy were clinical prognostic factors at diagnosis, while the difference remained or disappeared in the follow-up for OS and PFS. Results in subgroup of patients achieved CR and PR was consistent.
Conclusion: In the first-line chemoradiotherapy era, the survival probability for LS-SCLC increased and progression probability decreased over time. The influence of prognostic factors at initial diagnosis may change in the long-term follow-up.