Initial Clinical Outcomes of Stereotactic Body Radiotherapy (SBRT) Treatment of Multiple Synchronous Lung Lesions

Abstract

Stereotactic body radiotherapy (SBRT) treatment of early-stage inoperable non-small-cell lung cancer (NSCLC) patients has shown greater than 90% local control rates at 3 years. However, patients with significant co-morbidities who present with multiple synchronous lung masses may benefit from treatment of multiple lesions synchronously by either single isocenter volumetric modulated arc therapy (VMAT) flattening filter free (FFF) or a 3DCRT and IMRT system plans. The goal is to reduce treatment time and improve patient compliance. We report our initial clinical outcomes of cancer patients with multiple (<5) lung lesions synchronously treated with lung SBRT. Thirty patients with multiple peripherally located lung masses (two n = 27, three n = 2, five n = 1, total 65 lesions) were treated synchronously with either single isocenter non-coplanar VMAT-SBRT (23 patients) or Tomotherapy (7 patients). Respiratory control of target movement was accomplished with abdominal compression. Dose and fractionation varied but the most common prescriptions were 54 Gy/3 fractions and 50 Gy/5 fractions prescribed to 80% isodose line covering the planning target volume. Patients were treated every other day with a daily cone beam-CT/MVCT guided imaging. Average treatment time was less than 10 min /fraction for VMAT and 20 min/fraction for Tomotherapy. Outcomes evaluated include local control rates, radiation pneumonitis and rib toxicity. Median follow-up interval was 8 months (range, 2 to 21 months). The median age of patients treated was 75 years. 20 patients had primary lung disease and 10 patients had metastatic disease to the lung. All plans met RTOG compliance criteria for target coverage and dose to organs at risk and all patients tolerated SBRT treatment. Mean V20Gy was 7.8 ± 4% (range, 3.2-15.7%). Maximal and 1 cc of rib doses were 40 Gy and 31.5 Gy, respectively. Four patients died before follow up and two were lost to follow up. Three patients have initial post-treatment imaging pending. Of twenty-one patients, all achieved complete response to treatment with only one lesion of one patient progressing. However, 10 patients developed distant metastases. During the follow-up period, no patients had adverse pulmonary side effects, developed grade 2+ pneumonitis, chest wall pain or rib fracture. However, 50% of the patients developed radiographic changes that were asymptomatic in nature. Synchronous lung SBRT treatment using a single-isocenter VMAT plan or Tomotherapy to multiple lung lesions was fast, safe and highly effective, with promising initial clinical results in terms of local control rates and no adverse treatment related side effects to lung or ribs. Although ten patients developed either further distant metastases, the local control achieved of treated lesions could preserve the patient’s quality of life or delay systemic therapy. Longer clinical follow up of these patients is needed.