Pilot Study of the Safety and Efficacy of Dose Escalation in Stereotactic Body Radiotherapy for Peripheral Lung Tumors.

BACKGROUND: This pilot study aimed to evaluate the safety and efficacy of a dose escalation method for the treatment of peripheral lung tumors by administrating steep dose gradients in the target volumes via stereotactic body radiotherapy (SBRT).

PATIENTS AND METHODS: Patients with peripheral lung tumors were enrolled onto this study and treated with SBRT using a total dose of 70 Gy in 4 fractions at target isocenter, covering the planning target volume surface with 70% of the isodose. The primary end point was the rate of grade 2 or higher radiation pneumonitis (RP) within 1 year.

RESULTS: A total of 35 patients were enrolled onto this study between September 2014 and January 2016. Thirty-two patients with primary lung cancers and 3 patients with lung metastases were treated with SBRT. Grade 2 RP was observed in 4 patients within 1 year. No severe RP (grade 3 or higher) was observed within the follow-up period. The median follow-up period was 21.2 months (range, 4.2-31.7 months). Local recurrence was observed in a single patient with lung metastasis. No local recurrence was observed within the follow-up period in the 32 patients with primary lung cancer. The local control and overall survival rates at 2 years were 95.7% (95% confidence interval, 72.9-99.4) and 85.2% (95% confidence interval, 67.8-93.6), respectively.

CONCLUSION: This dose escalation method with steep dose gradients using SBRT for peripheral lung tumors was safe in the subacute phases. These results also suggest that this method can obtain excellent local control rates.