Steep dose-response relationship for stage I non-small cell lung cancer using hypo-fractionated high-dose irradiation by real-time tumor-tracking radiotherapy (RTRT)

Purpose: To investigate the clinical outcomes of patients with pathologically proven, peripherally located, stage I non-small cell lung cancer (NSCLC) who received stereotactic body radiotherapy (SBRT) using real-time tumor tracking radiotherapy (RTRT) during the developmental period. Materials and Methods: Forty-one patients were admitted (T1, 25; T2, 16) from February 2000 to June 2005. A 5 mm lanning target volume (PTV) margin was added to the clinical target volume determined with computed tomography at the end of expiratory phase. The gating window ranged from ± 2 to 3 mm. The dose fractionation schedule was 40 or 48 Gy in 4 fractions within 7 days. The dose was prescribed at the center of the PTV, giving more than an 80% dose at the PTV periphery. Results: For 28 patients treated with 48 Gy in 4 fractions, the overall actuarial survival (OAS) at 3 years was 82% for stage IA and 32% for stage IB. For patients treated with 40Gy/4Fr/1wk, OAS at 3 years was 50% for stage IA and 0% for stage IB. There was a significant difference in local control between 40 and 48 Gy in stage IB (p=0.0015) but not in stage IA (p=0.5811). No serious radiation morbidity was observed in either dose schedule. Conclusion: Forty-eight Gy in 4 fractions in one week was found to be a safe and effective treatment for peripherally located, stage IA NSCLC. A steep dose-response curve between 40 and 48 Gy using a daily dose of 12 Gy delivered in one week was identified for stage IB NSCLC in SBRT using RTRT.