Long Term Clinical Outcomes of a Cohort of Lung-Only Oligometastatic HNSCC Patients Treated with SBRT

Abstract

Oligometastatic disease in head and neck squamous cell carcinoma (HNSCC) is a rare setting. Local ablative therapies are the most adopted strategies although no evidence-based recommendations are currently published. The aim of our analysis was to update and report on long-term clinical outcomes of a cohort of HNSCC patients treated with stereotactic body radiotherapy (SBRT) for lung-only oligometastatic disease. Eligible patients had 1 to 5 lung metastases. The oligometastatic pattern was classified as "de novo" (suitable for SBRT only) or "oligoprogressive" (after first line of systemic therapy). We evaluated time to progression (TTP) as the time from the last day of SBRT to disease progression or death from any cause. Predictive factors of better clinical outcome and survival analysis were performed by Cox regression and Kaplan Meier methods, respectively. A cohort of 46 patients and 47 metastases were retrospectively evaluated. The median age was 67 years (range 37-86) and 87% of patients had a ECOG PS 0-1. HPV negative status (77%) and "de novo" oligometastatic pattern (78%) were reported by the majority of patients. After a median follow up of 28 months (range 2-88), median TTP and overall survival (OS) were 18 months (95% CI 4.8 - 31.2) and 62 months (95% CI 10,8 - 113.2), respectively. The median volume of planning target volume (PTV) was 20.4 cc (range 7.1-55.3). At univariate analysis, patients aged > 70 years reported a better TTP (p 0.013). No statistically significant correlation was observed in respect with gender (p 0.23), ECOG PS (p 0.34), oligometastatic pattern (p 0.13) and p16/HPV status (p 0.22). Out of 26 histologically proven metastases, we collected only 2 patients reporting concordance between p16/HPV positive status of primary tumor and lung metastases. Overall, 6 patients reported grade (G) 1-2 acute toxicity and no acute G3 adverse events were observed. Our findings suggested that SBRT may improve clinical outcome prolonging time to progression and to systemic treatments in a properly selected cohort of HNSCC patients with lung-only oligometastatic disease. Distant metastases from HPV-related primary HNSCC should be tested for p16/HPV status given the clinical implications of HPV positivity for diagnosis and treatment.