Influence Factors And Prognostic Value Of Tumor Regression After Intensity-modulated Radiotherapy In Limited-stage Small Cell Lung Cancer

Purpose:1.To investigate the tumor regression of limited-stage small cell lung cancer (LS-SCLC) after intensity-modulated radiation therapy(IMRT) and analyze possible factors that influence the tumor regression after radiotherapy.2.To evaluate the effect of tumor regression on the overall survival rate of LS-SCLC after intensity-modulated radiation therapy.Methods and Materials: Patients with LS-SCLC treated with IMRT in the author’s hospital between August2009and September2013were enrolled in this study. All of the patients had a ECOG score of0-2and received no operation. Clinical data including chest computed tomography (CT) images were collected before and after radiotherapy retrospectively and tumor volume was measured using Treatment Planning System(TPS) and Image J. Logistic regression was used to analyze the effect of age, pre-radiotherapy volume, number of chemotherapy cycles before radiotherapy and radiotherapy dose on tumor regression. As for survival analysis, survival rate calculations were performed by Kaplan-Meier method. Log-rank method was used in the univariate analysis of age, major classification, T staging, pre-radiotherapy volume, number of chemotherapy cycles before radiotherapy, radiotherapy dose and tumor regression rate. Cox proportional hazards regression was used in the multivariate analysis of age, pre-radiotherapy volume, number of chemotherapy cycles before radiotherapy, radiotherapy dose and tumor regression rate.Results:25cases were adopted in our study with a pre-radiotherapy volume of37.2±42.6cm3and a post-radiotherapy volume of22.5±27.2cm3, the volume reduction rate(VRR) being37.37±24.07%. Among them,7cases had a VRR≥50%,18cases had a VRR <50%. Multiple logistic regression analysis suggested that there was no significant difference in factors that may influence the tumor regression after radiotherapy. The median survival time (MST) for the25cases was20months and the1-and2-year overall survival rates(OS) were 59.6%and45.0%respectively. We also found that the effect of age(P=0.044), radiotherapy dose(P=0.008) and VRR(P=0.013) on total survival had significant difference based on Cox survival analysis. The1-year OS for patients less than60years old and more than60years old were72.0%and44.9%respectively. The1-year OS for patients with a radiotherapy dose＜50Gy and>50Gy were27.8%and69.7%respectively. The1-year OS for patients with a tumor regression <50%and≥50%were65.3%and32.1%respectively.Conclusion: No single factor influencing the tumor regression of LS-SCLC after radiotherapy was found in our study. Age, radiotherapy dose and VRR were independent prognostic factors of LS-SCLC. Older age, lower radiotherapy dose and higher VRR indicated poor prognosis.