Dissemination patterns and chronology of distant metastasis affect survival of patients with head and neck squamous cell carcinoma

Objectives: To define metastatic categories based on their prognostic significance. We hypothesized that oligometastasis in patients with head and neck squamous cell carcinoma (HNSCC) is associated with better postdistant metastasis disease specific survival (post-DM DSS) compared to patients with polymetastasis. Furthermore, the impact on survival of synchronous versus metachronous distant metastasis (DM) occurrence was assessed. Materials and methods: Retrospective cohort study in which patients with DM were stratified into three groups: oligometastasis (maximum of 3 metastatic foci in <= 2 anatomic sites), explosive metastasis (>4 metastatic foci at one anatomic site) and explosive-disseminating metastasis (spread to >3 anatomic sites or >3 metastatic foci in 2 anatomic sites). In addition, patients were divided into synchronous versus metachronous DM. Results: Between January 1, 2006 and December 31, 2013, a total of 2687 patients with HNSCC were identified, of which 324 patients developed DM. In this group, 115 (35.5%) patients had oligometastasis, 64 (19.8%) patients had explosive metastasis and 145 (44.8%) patients had explosive-disseminating metastasis. Their median post-DM DSS were 4.7 months, 4.1 months and 1.7 months respectively (p < .001). Synchronous DM was associated with more favorable survival rates in univariable and multivariable analyses than metachronous DM with recurrence of the index tumor (6-month post-DM DSS probability of 0.51 vs 0.17, p < .001). Conclusion: Oligometastasis in HNSCC signifies a better prognosis than a polymetastatic pattern. Metachronous DM occurrence with recurrence of the primary index tumor is associated with an unfavorable prognosis.