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

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. 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. 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). PTS may impact the response to nivolumab in HNSCC patients.