Abstract
I compliment Geraily et al 1 on their paper related to assessing the risk of secondary cancer induction during trigeminal neuralgia treatment with high-dose, gamma-knife radiosurgery. Secondary-cancer-induction risk related to the out-of-field, gamma-ray exposure was assessed using the National Academies BEIR VII Phase 2 Report methodology (reviewed for low-dose applications and solid cancers by Taylor and Kron 2 ). For solid cancers, the methodology is linked to linear no-threshold (LNT) theory for cancer induction. Time-after-exposure-dependent, excess absolute risk (EAR) and excess relative risk (ERR) are assigned numerical values based on LNT functions of radiation dose. 2
It is important to point out to Geraily and colleagues that LNT theory for cancer induction is now known to not be supported by radiobiological data (reviewed elsewhere 3 ), which supports a > 0 Gy population threshold dose for radiation-caused cancer. Below the threshold, natural defenses (including protective radiation adaptive responses) serve as barriers to cancer. 3 With LNT theory for cancer induction, both EAR and ERR for a gamma-ray dose of 1000 nGy are assigned illogical values 1000 times larger than the assigned > 0 values for a harmless 1 nGy dose. 4
The illogicalness of LNT theory for cancer induction is revealed by the fact that even though we humans reside in a sea of natural background ionizing radiation, we have not perished from Earth, but remain in large numbers. We are exposed to gamma-ray photons (related to cosmic rays 5 and thunderstorms 6 ) and other natural background radiation throughout our lives, including photons with energies 5 > 10 GeV. Unfortunately, some influential epidemiologists still rely on LNT models for cancer risk assessment. They however employ misinforming procedures in their data analyses that can essentially guarantee apparent LNT results.4,7 It is recommended that cancer risks (EAR, ERR) associated with out-of-field, gamma-ray exposure, related to gamma-knife radiosurgery, not be assigned based on BEIR VII LNT models. This is because for low radiation doses (e.g., < 0.1 Gy), the assigned values for EAR and ERR are likely to be unreliable and promote secondary-cancer-related, radiation phobia among patients that undergo radiosurgery. 3
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
