Escalated Maximum Dose in the Planning Target Volume Improves Local Control in Stereotactic Body Radiation Therapy for T1-2 Lung Cancer

SIMPLE SUMMARY: Stereotactic body radiotherapy (SBRT) is a treatment option for early-stage lung cancer. The purpose of this study was to investigate the optimal dose distribution and prognostic factors for local control (LC) in 100 patients with lung cancer who underwent SBRT. The 1- and 3-year LC rates were 95.7% and 87.7%, respectively. In summary, we found that squamous cell carcinoma (SQ), T2 tumor stage, and a lower radiotherapy dose were associated with poorer LC in lung cancer. The lower rate of LC in patients with SQ vs. non-SQ was limited to cases with a Dmax below 125 Gy (BED(10)). ABSTRACT: Stereotactic body radiotherapy (SBRT) is a treatment option for early-stage lung cancer. The purpose of this study was to investigate the optimal dose distribution and prognostic factors for local control (LC) after SBRT for lung cancer. A total of 104 lung tumors from 100 patients who underwent SBRT using various treatment regimens were analyzed. Dose distributions were corrected to the biologically effective dose (BED). Clinical and dosimetric factors were tested for association with LC after SBRT. The median follow-up time was 23.8 months (range, 3.4–109.8 months) after SBRT. The 1- and 3-year LC rates were 95.7% and 87.7%, respectively. In univariate and multivariate analyses, pathologically confirmed squamous cell carcinoma (SQ), T2 tumor stage, and a Dmax < 125 Gy (BED(10)) were associated with worse LC. The LC rate was significantly lower in SQ than in non-SQ among tumors that received a Dmax < 125 Gy (BED(10)) (p = 0.016). However, there were no significant differences in LC rate between SQ and non-SQ among tumors receiving a Dmax ≥ 125 Gy (BED(10)) (p = 0.198). To conclude, SQ, T2 stage, and a Dmax < 125 Gy (BED(10)) were associated with poorer LC. LC may be improved by a higher Dmax of the planning target volume.