Pre-treatment tumor size impacts on response to nivolumab in head and neck squamous cell carcinoma.

OBJECTIVE: Baseline tumor size has been reported to be predictive of immune checkpoint inhibitor efficacy in melanoma and lung cancer. We investigated whether pre-treatment tumor size (PTS) is predictive of progression-free survival (PFS) and tumor shrinkage in head and neck squamous cell carcinoma (HNSCC) patients treated with nivolumab. METHODS: We retrospectively assessed 37 patients who had measurable tumor lesions. PTS and post-treatment tumor size were defined as the sum of the size in all measurable lesions. RESULTS: In univariate analysis, PTS below 42 mm, history of radiation therapy, and no use of cetuximab were significantly associated with longer PFS. Among them, small-PTS was an independent predictive factor for PFS in multivariate analysis (hazard ratio: 0.33, p = 0.022). In addition, significantly greater tumor shrinkage was observed for small-PTS than large-PTS (median: -10.0% vs. 23.1%, p = 0.033). CONCLUSION: PTS may impact the response to nivolumab in HNSCC patients.