Cell survival and DNA damage in normal prostate cells irradiated out-of-field

Area of Science:

• Radiation Oncology
• Cell Biology
• Radiobiology

Background:

• Volumetric Modulated Arc Therapy (VMAT) increases out-of-field radiation exposure to normal tissues.
• The biological impact of low-dose, out-of-field radiation, including bystander effects and energy spectrum changes, is not fully understood.
• New radiotherapy techniques necessitate understanding their effects on normal tissue radiobiology.

Purpose of the Study:

• To investigate the effects of out-of-field radiation on normal prostate cell survival and DNA damage.
• To examine the influence of radiation-induced bystander factors on normal cells exposed to out-of-field radiation.
• To assess the impact of altered energy spectra on cells receiving out-of-field radiation.

Main Methods:

• Normal prostate cells (PNT1A) were exposed to out-of-field radiation during VMAT delivery to prostate cancer cells (LNCaP).
• Clonogenic and γ-H2AX assays were used to measure cell survival and DNA damage.
• Experiments included transfer of bystander factors and irradiation with different energy spectra.

Main Results:

• An average out-of-field dose of 10.8 cGy significantly reduced colony volume and increased DNA damage (γ-H2AX foci) in PNT1A cells.
• An adaptive response was observed in PNT1A cells pre-exposed to low-dose out-of-field radiation followed by bystander factor transfer.
• No significant difference in cell survival or colony volume was found between in-field and out-of-field irradiation, despite increased DNA damage in the latter.

Conclusions:

• Out-of-field radiation, even at low doses, can impair normal prostate cell proliferation.
• The transfer of bystander factors following low-dose out-of-field exposure can induce a protective adaptive response.
• Further research is needed to fully elucidate the long-term radiobiological consequences of VMAT on normal tissues.