ESTRO 2021 Abstract Book

S984

ESTRO 2021

PO-1186 Treatment outcomes of stereotactic body radiotherapy for lung cancer according to tumor appearances Y. Hamamoto 1 , K. Makita 1 , H. Kanzaki 1 , K. Nagasaki 1 1 Shikoku Cancer Center, Radiotherapy, Matsuyama-city, Japan Purpose or Objective Lung cancer mainly with a ground glass appearance (GGA tumors) often progresses slowly, and usefulness of aggressive stereotactic body radiotherapy (SBRT) for these tumors has not been clarified. Treatment outcomes of SBRT for GGA tumors were assessed with comparing to those of lung cancer with mainly solid component (solid tumors). Materials and Methods Ninety-eight patients (age, 49-90; median, 79) received SBRT for primary lung cancer. Among these patients, 21 patients had GGA tumors and 77 patients had solid tumors. The principle prescribed dose of SBRT was 48 Gy in four fractions at the isocenter. Results Median follow-up time was 52 months for all patients and 82 months for patients alive at the last follow-up. For GGA tumors, the 5-year local control (LC) rate was 100%. For solid tumors, the 3-year and 5-year LC rates were 84% and 71%, respectively. The differences of LC rates were statistically significant (p=0.0389). The 3- year and 5-year overall survival (OS) rates were 85% and 65% respectively for GGA tumors, and 59% and 40% respectively for solid tumors (p=0.0335). Conclusion For both GGA tumors and solid tumors, there were significant discrepancy between LC rates and OS rates. High LC rates of GGA tumors did not necessarily lead to high OS rates. Because of slow growing of GGA tumors,