Stereotactic Ablative Radiation Therapy (CyberKnife) for Lung Oligometastases from Head and Neck Squamous Cell Carcinoma (HNSCC): Bi-Institutional Study

Abstract

The aim of this study was to assess clinical benefit of Stereotactic Ablative Body Radiation (SABR) for lung oligometastases from head and neck squamous cell carcinoma (HNSCC). Outcomes of patients with HNSCC with controlled primary tumor and presenting up to two evolutive lung metastases (<5cm) treated with SABR (CyberKnife) were retrospectively reviewed from our two French institutions. Lung metastases could have been screened by CT or PET- CT only and histological proof was not mandatory. Multidisciplinary tumor board was required to validate the indication of curative intent SABR in all cases. Between November 2007 and February 2018, 57 patients were identified in our database. Median age was 67 (50-83). Median time from treatment of the primary HNSCC to development of lung metastases was 18 months (0-93). Most had metachronous metastases (93%) rather than synchronous. The majority of patients received 60Gy in 3 fractions. 45 patients (79%) presented a solitary lung metastasis while 12 patients (21%) had 2 lung secondary lesions. With a median follow-up of 25.3 months, crude local and metastatic recurrences rates were 27.3 % and 61.8% respectively. 1 year and 2-year progression free survival (PFS) were 52.3% and 28% respectively. Median PFS was 14 months. 1 year and 2-year Overall Survival (OS) 87% and 66.8%. The median OS was 48.3 months. The treatment was well tolerated with only one patient who reported ≥ grade 3 toxicity (1.7%). In patients with a controlled primary tumor and limited number of metastases, a radical approach with SABR can be considered as an effective treatment. Prospective studies are needed to identify which patients benefit for such strategy.