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Outcome of Stereotactic Body Radiotherapy for Patients with Histologically Proven Stage I Non-Small-Cell Lung Cancer

      Purpose/Objective(s)

      Stereotactic body radiotherapy (SBRT) is a definitive local treatment for patients with early-stage non-small-cell lung cancer (NSCLC). The purpose of this study was to analyze our institutional experience using SBRT in patients with early-stage NSCLC.

      Materials/Methods

      From 2009 through 2016, 411 consecutive patients with lung tumor were treated with SBRT at our center in Japan. One-hundred-fifty patients with clinically staged, histologically proven Stage I NSCLC (median age, 80 years; T1aN0M0, n = 53; T1bN0M0, n = 59; T2aN0M0, n = 38) were included in this study. Patients with follow-up of <6 months and with no events of recurrence or death were excluded. The histology was adenocarcinoma in 100 patients, squamous cell carcinoma in 44 patients, and others in 6 patients. SBRT was performed using non-coplanar, static 6-MV photon beams. Prescription dose was 48 Gy in 4 fractions (n = 122), 60 Gy in 8 fractions (n = 19), 60 Gy in 10 fractions (n = 4), and others (n = 5). Data were collected and analyzed retrospectively. The overall survival (OS), the local control (LC), and the relapse-free survival (RFS) after initial radiotherapy were estimated by Kaplan-Meier method.

      Results

      Median durations of observation for all patients and survivors as of the final follow-up were 38.0 (range, 2.8-98.6) and 45.8 (range, 6.0-98.6) months, respectively. The 3-year OS, LC, and RFS were 76.7% (95% confidence interval [CI], 68.4-83.0%), 79.1% (95% CI, 70.1-85.7), and 63.1% (95% CI, 53.9-70.9%), respectively. The 5-year OS, LC, and RFS were 61.2% (95% confidence interval [CI], 50.2-70.4%), 77.6% (95% CI, 68.1-84.5), and 60.4% (95% CI, 50.8-68.7%), respectively. Disease progression was observed in 50 patients. After long-term follow-up, local, nodal, and distant failure occurred in 24, 24, and 31 patients, respectively. Local, nodal, and distant failure occurred at a median 17.1 (range, 6.9-45.6) months, 14.6 (range, 1.2-65.6) months, and 13.0 (range, 3.4-51.2) months, respectively. In 23 patients (95.8%), local failure occurred within 3 years. On univariate analysis, squamous cell carcinoma, tumor size, the history of smoking, and male were associated with an increased risk for OS. But all of them were not associated with an increased risk for LC. Radiation pneumonitis of Grade 5 was observed in 2 patients. Both received SBRT twice.

      Conclusion

      In this study, LC is relatively high. However, local failure is the second reason for recurrence next to distant failure. To prevent local failure, dose escalation should be considered.

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