Our recent data has also shown that the PARP inhibitors olaparib and talazoparib can synergistically act with low-LET photons and protons to radiosensitise HNSCC cells grown as 3D spheroids, and where greater radiosensitisation occurred in HR-deficient compared to HR-proficient cells [40]. Here, PARP1 is linked to head and neck squamous cell carcinoma.