JCCA 2006;50 (3):172–181. Oakley P, Harrison DD, Harrison DE, Haas J. A Rebuttal to Chiropractic Radiologists’ View of the 50 year old, Linear-No-Threshold Radiation Risk Model (Commentary).

To the Editor:

Potential harmful effects versus clinical benefits of radiography remain a significant concern and topic of debate in the chiropractic profession.¹ Oakley et al.² proposed the chiropractic profession review radiography standards and regulations implying there may be more good than harm from diagnostic ionizing radiation exposure. However, the preponderance of evidence does not support abandoning current standards and regulations as explained in our recent commentary.³ This letter is in response to Oakley P, Harrison DD, Harrison DE, Haas J. A Rebuttal to Chiropractic Radiologists’ View of the 50 year old, Linear-No-Threshold Radiation Risk Model (J Can Chiropr Assoc 2006, 50 (3): 172–181).⁴

Unfortunately, further attempts by Oakley P, Harrison DD, Harrison DE, Haas J. to justify their position has not helped further the discussion.⁴ The critiques presented by Tubiana, Aurengo^5,6 to the microdosimetric arguments that support linear no-threshold do not seem to be valid.⁷ Furthermore, there is no convincing evidence to support the suggestion that immune surveillance will differentially decrease cancer risks at very low doses, and there is some evidence to the contrary. According to Brenner and Sachs,⁷ proposed data summarized in the both the French Academy report⁵ and US National Academy BEIR VII report,⁸ suggest that we currently know little of the magnitude of inter-cellular communication effects on radiation carcinogenesis in vivo. «It seems therefore premature to use arguments about inter-cellular interactions to justify replacing linearity in cancer risk at very low doses with any non-linear dose – response relationship».⁷

It is essential to emphasize that routine use of conventional radiography is simply not acceptable by any health care profession. As previously stated in our commentary,³ one of the three basic principles of radiation protection that is most applicable is:

«No practice involving exposure to radiation should be adopted unless it produces sufficient benefit to the exposed individual or to society to offset the radiation detriment it causes».

The only clinical trial Oakley¹ could propose indicating a clinical benefit related to conventional radiography is the recent article by Khorshid et al.⁹ published in a non peer review journal. Well designed large randomized clinical trials are needed before concluding routine use of radiography has any demonstrable clinical benefits, either in children with autism treated by upper cervical spine care, or for any of the common conditions treated by chiropractors.

In conclusion, we stand by our commentary. However interesting the radiation hormesis theory may appear on the surface, it remains speculative and untestable. Until new standards in radiographic protection are established by international, national, and state organizations – an unlikely occurrence – routine use of conventional radiography should not be advocated or tolerated in any profession, including chiropractic, even if patients appear more satisfied or because a particular technique system advocates it.

The first and most important duty of health care professionals is to serve the best interests of patients. This entire debate brought forward by Oakley et al. may stem from the natural fear by practitioners of seeing their individual practices limited by adopting sound clinical guidelines based on appropriate and recognized indications for imaging studies. Evidence-based clinical and diagnostic imaging guidelines are intended to improve patient health outcome and quality of care, reduce unnecessary radiation exposure and practice variation, and encourage more efficient use of resources. In all cases, guidelines are intended to be used in conjunction with sound clinical judgement and experience. Such clinical indications for imaging studies are being developed by and for the chiropractic profession (available on online at: http://www.uqtr.ca/imagingchiroguidelines). Chiropractors world wide are invited to visit this site.