Stereotactic Body Radiotherapy of Central Lung Malignancies Using A simultaneous Integrated Protection Approach : A prospective Observational Study

Aim: It is recognized that stereotactic body radiotherapy (SBRT) for centrally located lung metastases is affected by higher rates of severe toxicity. In the present study, we report the clinical outcomes following a novel intensity-modulated radiotherapy prescription dose, termed simultaneous integrated protection (SIP), for nearby organs at risk (OARs).

Materials And Methods: The prescribed total doses of SBRT were 70 Gy in 10 fractions and 60 Gy in 8 fractions. For ultra-centrally located lesions, a dose of 60 Gy in 10 fractions was delivered. The main planning instructions were: (1) to remain within the limits of the given dose constraints for an OAR; (2) to make use of the maximum possible dose to the OARs to minimize dose inhomogeneity for the Planning Target Volume (PTV). SBRT-related toxicity was prospectively assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) v4.0. The primary clinical endpoint was the SBRT-related toxicity. Secondary endpoint was local control.

Results: Forty patients affected by a single central malignancy were analyzed. The median follow-up was 20 months (range, 6-58 months). Acute and late clinical pulmonary toxicity ≥grade 2 was recorded in 2 out of 40 patients (5%) and 3 out of 40 patients (7%), respectively. No patient experienced cardiac toxicity. No narrowing or stenosis of any airway or vessel was registered. One-year local control rate was 91%. The median time to local progression was 13 months (range, 6-46 months).

Conclusion: SBRT using a PTV-SIP approach for single central lung metastases achieved low SBRT-related toxicity with acceptable local control.