Stereotactic Body Radiotherapy (SBRT) for Multiple Synchronous Oligometastases (< 5) Lung Lesions: Early Clinical Outcomes

Abstract

Lung cancer patients with multiple oligometastases (< 5) lesions with associated co-morbidities may not retain their treatment position for the extended Stereotactic Body Radiotherapy (SBRT) treatment times with individual isocenters for each lesion due to distress or shortness of breath. SBRT of multiple lung lesions synchronously (in one course) using a single-isocenter volumetric arc therapy (VMAT) plan with flattening filter free (FFF) beam or tomotherapy will shorten treatment courses, improve patient comfort by reducing treatment time, and improve clinic efficiency. We report our early clinical results of treating oligometastatic lung disease with synchronous single-course lung SBRT.Fifty-six patients with multiple oligometastatic lung lesions (two n = 51, three n = 4, five n = 1, total 119 lesions) were treated synchronously with either highly conformal single-isocenter non-coplanar VMAT-SBRT (49 patients) or tomotherapy (7 patients). The most common prescriptions were 50-55 Gy/5 fractions or 54 Gy/3 fractions prescribed to 70-80% isodose line. The VMAT-SBRT plans were calculated with an advanced dose calculation algorithm for 6 MV-FFF beam and tomotherapy used superposition/convolution algorithm (with 6MV) for heterogeneity corrections. All plans were evaluated with RTOG-0618/0813 criteria. Treatments were delivered every other day with daily cone beam-CT/MVCT guidance. Highly conformal SBRT treatments were delivered in less than 10 min per fraction, on average. Local control rates, radiation-induced pneumonitis and rib toxicity were determined. Mean follow up interval was 11.4 months (range, 2.1 to 35.3 months).All plans met RTOG-0618/0813 requirements for target(s) coverage, dose to organs at risk including lung and ribs and all patients tolerated SBRT. Six patients died before follow up and five were lost to follow up. Five patients have initial post-treatment imaging pending. Of forty evaluable patients, all achieved complete response to SBRT in all lesions. However, 18 patients developed distant metastases. During the follow-up interval, almost 50% of the patients developed radiographic changes that were asymptomatic in nature, however no patient developed grade+2 (or higher) pneumonitis, had rib fracture or developed chest wall pain.A single course of lung SBRT to synchronous multiple lung lesions using a single-isocenter VMAT plan or tomotherapy is feasible, fast, safe and highly effective, with promising early local control rates and no adverse pulmonary side effects or rib toxicity. Although 18 patients developed distant metastases, the local control achieved in the treated lesions could preserve the patient's quality of life or delay systemic therapy even in these patients. Longer clinical follow up is warranted and planned.L. Downes: None. D. Pokhrel: None. L. Critchfield: None. M.E. Bernard: None. M.E. Randall: None. R.C. McGarry: None.