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Abstract

INTRODUCTION:
The purpose of this study was to assess the effect of dose escalation of stereotactic ablative radiotherapy (SABR) by investigating the long-term clinical outcomes of SABR for stage I non-small-cell lung cancer (NSCLC).

METHODS:
A retrospective analysis was performed on a total of 169 patients with 178 lesions of stage I NSCLC treated with SABR at a single institution from June 2000 to May 2015. The standard dose scheme for SABR was 48 Gy in 4 fractions during the early period of the analysis, but it was escalated to 60 Gy in 4 fractions from June 2009. All failures were recorded over the follow-up period.

RESULTS:
Median follow-up time was 32 months. The 5-year overall survival rate was 46.7%, and the actuarial local control rate was 79.3%. Tumor size was an independent prognostic factor for survival. No relapse occurred in tumors ≤ 2 cm irrespective of SABR dose. Escalated doses of approximately 60 Gy in 4 fractions (biologically effective dose [BED] = 150 Gy10) achieved higher local control compared with 48 Gy in 4 fractions (BED = 106 Gy10) (76.2% vs. 60.6%) at 5-year follow-up (P = .022) in tumors > 2 cm. There were no differences in treatment-related toxicities between the dose groups. Major failures consisted of distant metastasis to another lung parenchyma.

CONCLUSION:
SABR provides satisfactory long-term local control and high overall survival in medically inoperable stage I NSCLC. Tumors ≤ 2 cm had no local recurrence regardless of dose; whereas for tumors > 2 cm, an escalated BED of approximately 150 Gy10 provided significantly higher local tumor control.

Author information

Lee S1, Song SY2, Kim SS1, Choi W3, Je HU4, Back GM5, Cho B1, Jeong SY6, Choi EK7.

1 Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2 Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. Electronic address: siyeol.song@gmail.com.
3 Department of Radiation Oncology, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea.
4 Department of Radiation Oncology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea.
5 Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea; Department of Medical Health Science, Kangwon National University Graduate School, Chuncheon, Korea.
6 Asan Institute for Life Science, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
7 Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. Electronic address: ekchoi@amc.seoul.kr.