A persistence of IR-induced DSBs measured via γH2AX/53BP1 foci was discovered in one report [9], whereas more conclusively γH2AX foci as well as IR-induced DSBs measured directly by neutral comet assays (albeit in only one HPV-positive HNSCC cell line) were shown to persist in HPV-positive versus HPV-negative HNSCC cells [12]. This evidence concerns the gene TP53BP1 and head and neck squamous cell carcinoma.