SU-F-T-112: Long-Term Follow-Up of NSCLC Patients Treated with Lung SBRT Using the Modified Conformal Arc (MDCA) Planning Technique.

PURPOSE: To assess long-term toxicity and primary tumor changes for Stage I/II non-small cell lung carcinoma (NSCLC) patients after treatment with lung SBRT using the modified dynamic conformal arc (MDCA) planning technique.

METHODS: Clinical and radiograph data from electronic health records of 15 NSCLC patients treated with lung SBRT utilizing the MDCA technique between October 2011 and July 2014 were retrospectively reviewed. MDCA uses a coplanar beam arrangement, patient body center for the beam isocenter, and six partial rotation conformal arcs to target the tumor. Radiation Therapy Oncology Group (RTOG) guidelines for treatment parameters were followed. Most patients received 5 radiation fractions (Range: 3 to 7 fractions) with 48 hours between each fraction. Median total dose was 60 Gy (range: 45 to 70 Gy).

RESULTS: Median follow-up was 18 months (range: 6-51 months). Median age was 72.5 years (range: 48-90 years). Post-treatment findings included fatigue (n = 5) and chronic chest wall pain (n=1). Seven patients reported respiratory symptoms, which included: cough (n = 4), dyspnea (n = 5), and hemoptysis (n = 1). No patients deaths or grade ≥4 toxicity were recorded. Radiographic scarring was seen on computed tomography (CT) imaging in 6 patients. Local control rate was 93.3% (n = 14) and 1 patient had local recurrence.

CONCLUSION: Our results were very similar to RTOG 0236 findings reported by Timmerman et al. - our local control rate was 93.3% compared to their 3-year primary tumor control rate of 97.6%. Toxicity rates were also similar - RTOG 0236 constitutional symptoms and pulmonary/upper respiratory symptoms rates were 36.4% and 60.0%, respectively, while ours were 33.3% and 46.7%, respectively. We were limited by a small sample size and relatively short follow-up but our findings support the use of the MDCA technique for lung SBRT treatment of Stage I/II NSCLC.