Duration of Twice-Daily Thoracic Radiotherapy and Time From the Start of Any Treatment to the End of Chest Irradiation as Significant Predictors of Outcomes in Limited-Disease Small-Cell Lung Cancer

BACKGROUND:The hypothesis of this retrospective study was that the duration of twice-daily (BID) thoracic radiotherapy (TRT) and time from the start of any treatment to the end of chest irradiation (SER) would predict outcomes in limited-disease small-cell lung cancer. MATERIALS AND METHODS:All 81 patients received 45 Gy in 30 fractions BID with a ≥ 6-hour interval and concurrent chemotherapy of platinum and etoposide. RESULTS:The median radiotherapy duration was 25 days (range, 21-38 days). The 5-year overall survival rates were 26.2% (95% confidence interval [CI], 14.3%-38.0%), and the median survival time was 30 months (95% CI, 15.5-44.5 months). Using multivariate regression analysis, the significant predictors of survival were the sum of the diameters of the primary tumor and metastatic lymph nodes, male gender, age ≥ 60 years, and the duration of BID-TRT (hazard ratio [HR], 1.15; 95% CI, 1.06-1.25; HR, 2.38; 95% CI, 1.13-5.02; HR, 2.38; 95% CI, 1.10-5.17; and HR, 1.08; 95% CI, 1.01-1.15, respectively). A total of 70 of 81 patients (86%) received radiotherapy during the first chemotherapy cycle. The median SER was 29 days (range, 21-109 days). The 5-year local control rate was 48.7% (95% CI, 33.9%-63.6%). The significant predictors of local control were the sum of the diameters of the primary tumor and metastatic lymph nodes, age ≥ 60 years, and SER (HR, 1.18; 95% CI, 1.06-1.31; HR, 4.18; 95% CI, 1.23-14.24; and HR, 1.02; 95% CI, 1-1.04, respectively). CONCLUSIONS:The duration of BID-TRT and SER were identified as one of the significant predictors of survival and local control in limited-disease small-cell lung cancer treated with concurrent chemoradiotherapy at 45 Gy in 30 fractions, respectively.