TUCSON, Ariz., Dec. 14, 2017 /PRNewswire-USNewswire/ -- According to the linear no-threshold theory, any dose of ionizing radiation greater than zero increases cancer risk. Evidence of actual excess cancers attributed to low doses is, however, generally restricted to thyroid cancer, write Jerry Cuttler, D.Sc., et al., in the winter issue of the Journal of American Physicians and Surgeons. The authors examine common pitfalls in studies that claim to show evidence of radiation-induced cancer, based on mass population screening for thyroid cancer.
Screening leads to enormous overdiagnosis, they write. "Excess" cancers identified by screening are limited to the papillary type, the most indolent type. "The natural history of thyroid cancer strongly suggests the existence of self-limiting cancers, which are truly malignant but do not progress to lethal cancers, a first-time observation in the history of medicine." The "early detection" of a self-limiting cancer, they note, can lead to unnecessary treatment such as thyroidectomy, with attendant harms.
Screening after a low-dose radiation exposure may lead to a spurious increase because such cancers are likely present but undetected in an unexposed but unscreened population.
The fear of cancer has led to the ALARA (as low as reasonably achievable) policy for radiation protection. This is not benign and prudent insurance, the authors argue. Costly measures, themselves quite harmful, may be implemented, such as unnecessary evacuations, or restrictions in the use of beneficial nuclear technology for medical diagnosis and treatment or energy production.
Radioiodine has been employed to treat hyperthyroidism for more than 70 years, and we have data on accidental high-dose exposures and atomic bomb survivors. The authors suggest a threshold level of at least 500 mSv, below which exposure in children is safe. Low-dose exposure is not only safe, they suggest, but actually beneficial because it stimulates adaptive protection systems that also protect against spontaneous cancers.
"DNA mutations overwhelmingly result from attack by reactive oxygen species, which are produced abundantly and constantly by aerobic metabolism," Cuttler et al. write. "All organisms have powerful protection systems, which prevent, repair, and remove damaged cells. The rate of mutation induction by low-level radiation is negligible when compared with the rate of endogenously induced mutations."
The Journal of American Physicians and Surgeons is published by the Association of American Physicians and Surgeons (AAPS), a national organization representing physicians in all specialties since 1943.
SOURCE Association of American Physicians and Surgeons (AAPS)