Heavy-Ion-Induced Lung Tumors: Dose- & LET-Dependence

Area of Science:

• Radiation biology
• Space medicine
• Oncology

Background:

• Limited data exists on low-dose, single-exposure charged particle radiation effects on in vivo tumorigenesis.
• Accurate risk assessment for particle radiation is crucial for manned space missions.

Purpose of the Study:

• To investigate the dose-response relationship of lung tumorigenesis after low single doses of various charged particle beams.
• To improve understanding of high linear energy transfer (LET)-dependent radiation-induced lung cancer risk.

Main Methods:

• Female CB6F1 mice were exposed to low single doses (0.03-0.80 Gy) of oxygen, silicon, titanium, or iron ions, and 137Cs gamma rays.
• Dose-averaged LET values ranged from 0.2-193 keV/µm.
• Tumor prevalence was assessed at 16 months post-irradiation, with 398 animals across 5 studies.

Main Results:

• Lung tumor prevalence exhibited a non-linear dose-response relationship.
• Evidence suggests the presence of threshold doses for lung tumorigenesis, dependent on beam LET.
• Predominant tumors were benign bronchioloalveolar adenomas, with some carcinomas and lymphosarcomas observed.

Conclusions:

• Low single doses of charged particle radiation can induce lung tumors in mice.
• The LET of the radiation significantly influences the dose-response and potential threshold for lung tumorigenesis.
• Findings contribute to better risk assessment for astronauts exposed to galactic cosmic rays.