The Effects of Ultra-High Dose Rate Proton Irradiation on Growth Delay in the Treatment of Human Tumor Xenografts in Nude Mice

Human papillomavirus status and the relative biological effectiveness of proton radiotherapy in head and neck cancer cells

“…We observed that more 53BP1 foci were present at 24 hours after a 4-Gy proton dose in the HPV-positive UMSCC-47 cells than in the HPV-negative HN5 cells, and the HPVpositive UMSCC-47 cells showed greater tail moment in the neutral comet assay, suggesting that persistence of double-strand breaks may be one explanation for the greater sensitivity of HPV-positive cells to proton therapy compared with HPV-negative cells. 22 6 0.19) or continuous (1.10 6 0.18) 46 ; however, other factors that potentially influence the RBE of HNSCC need to be addressed. [39][40][41][42] Currently, clinical use of proton therapy is based largely on experience with XRT-based therapy.…”

Report of the AAPM TG‐256 on the relative biological effectiveness of proton beams in radiation therapy

“…The proton RBE for tumor growth delay of NFSa (fibrosarcoma) in mice found a proton RBE of ~0.8 (at ~30 Gy relative to 180 kVp x rays; note that relative to 60 Co the RBE would be ~1.0) . The study of tumor growth delay of human hypopharyngeal squamous cell carcinoma cells in mice resulted in an RBE between 1.1 and 1.2 at ~20 Gy relative to 6 MV photons using a 23‐MeV proton beam . A study on the recurrence of mouse mammary carcinoma in mice resulted in an RBE of ~1.1 (at ~50 Gy relative to 60 Co) .…”

“…The local dose rate also differs between scanned beam delivery and passively scattered delivery. Whether ultra‐high dose rates in excess of 20 Gy/s show differential responses between murine normal and tumor tissues in vivo is controversial, effects of ultra‐high dose rates on biological response have not been found in vitro.…”

The radiobiology of laser-driven particle beams: focus on sub-lethal responses of normal human cells

“…Of fundamental importance to gain insights into laser-driven particle biological effectiveness is, of course, in vivo work. From these studies, mainly limited to tumour growth delay as endpoint of clinical relevance and still too scarce for firm conclusions to be drawn, no enhancing effects have emerged for both protons and electrons [38][39][40].…”