The effect of bioequivalent radiation dose on survival of patients with limited-stage small-cell lung cancer

BACKGROUND To investigate the biological radiation dose-response for patients of limited-stage small-cell lung cancer (LS-SCLC) treated with high radiation dose. METHODS Two hundred and five patients of LS-SCLC treated with sequential chemotherapy and thoracic radiotherapy with involved-field between 1997 and 2006 were reviewed retrospectively. Biologically effective dose (BED) was calculated for dose homogenization and was corrected with the factor of overall radiation time. Patients were divided into low BED group (n = 70) and high BED group (n = 135) with a cut-off of BED 57 Gy (equivalent to 60 Gy in 30 fractions over 40 days). Outcomes of the two groups were compared. RESULTS Median follow-up was 20.7 months for all analyzable patients and 50.8 months for surviving patients. Considering all patients, median survival was 22.9 months (95% confidence interval, 20.6-25.2 months); 2- and 5-year survival rates were 47.2% and 22.3%, respectively. Patients in high BED group had a significantly better local control (p = 0.024), progression-free survival (p = 0.006) and overall survival (p = 0.005), with a trend toward improved distant-metastasis free survival (p = 0.196). Multivariable Cox regression demonstrated that age (p = 0.003), KPS (p = 0.009), weight loss (p = 0.023), and BED (p = 0.004) were significant predictors of overall survival. CONCLUSIONS Our data showed that a high BED was significantly associated with favourable outcomes in the Chinese LS-SCLC population, indicating that a positive BED-response relationship still existed even in a relatively high radiation dose range.