Which term best describes the relationship of cancer risk to radiation exposure?

• A. Deterministic
• B. Random
• C. Unpredictable
• D. Stochastic

Answer: (D)

Cancer risk from radiation is a probabilistic, or random, effect. In radiobiology, effects are categorized as deterministic or stochastic. Deterministic effects have a threshold and become more severe as the dose increases, which isn’t how cancer behaves. Cancer risk isn’t guaranteed at a fixed dose and isn’t about a predictable level of damage that scales in severity with dose. Instead, as exposure increases, the probability that cancer will develop rises, even though not everyone exposed will cancer—this is a probability-based relationship. That combination of dose-dependent likelihood with no fixed threshold is captured by the term stochastic. The other terms are less precise: deterministic implies a threshold and a definite outcome, while random or unpredictable don’t convey the formal probabilistic, dose-response nature used in radiation protection.