CORR Insights®: Is the Lifetime Malignancy Risk in United States Military Personnel Sustaining Combat-related Trauma Increased Because of Radiation Exposure From Diagnostic Imaging?

Where Are We Now?

Medical devices represent the largest source of manufactured radiation exposure. Decreasing the adverse health effects of radiation exposure has been a focus for decades. These efforts have included decreasing the number of radiographs taken in standard series [2], using low-dose CT scan protocols [9], electronic exchange of images between transferring facilities [12], protective lead-rubber shields [6], and radiation safety training [5]. Despite the evidence of decreased radiation exposure associated with these interventions and changes, none of these is universally used.

The effect of multiple imaging studies on carcinogenesis has gained recent attention. Howard et al. [8] estimated the lifetime fatal carcinogenesis risk in patients with polytrauma as a function of radiation exposure in the first year after injury. It is understood that the risk of carcinogenesis is not associated with a scanner’s radiation output but the effective dose, which is a factor of the organ-specific dose. The risk of carcinogenesis is believed to be increased with dose exposure greater than 50 mSv [11]. Associations between radiation dose and carcinogenesis have been made primarily from atomic bomb survivors, occupational exposure research, and environmental radiation studies [4].

In a study of 3708 patients from a trauma registry in this month’s Clinical Orthopaedics and Related Research®, the authors of “Is the Lifetime Malignancy Risk in United States Military Personnel Sustaining Combat-related Trauma Increased Because of Radiation Exposure From Diagnostic Imaging?” [1] agreed that limiting radiation exposure in patients sustaining trauma is preferrable. Based on the results of this study, surgeons need to recognize the cumulative exposure to iatrogenic radiation in patients with multitrauma. The potential for carcinogenesis is higher than anticipated.

Where Do We Need To Go?

Much like the study by Howard et al. [8], who reported a single institution’s 10-year experience, the current study [1] reported the cumulative radiation exposure of servicemembers sustaining combat- and noncombat-related trauma over a 13-year period. The results here were equally concerning. One-year radiation exposure exceeded levels predictive of carcinogenesis for a substantial portion of study participants. Although the current study draws increased attention to this key point, there are several questions worthy of further investigation.

For example: What is the contribution of radiation exposure by specific radiographic study type? What is the level of exposure sustained by body region (upper extremity, lower extremity, spine, and pelvis), and how does this relate to the organ-specific dose? What are the actual incidences of radiation-induced carcinogenesis compared with rates predicted by current models? What is the incidence of adverse effects for conditions other than carcinogenesis, such as cataracts and thyroid disease? What proportion of exposure occurs during successive timepoints through the first year (preoperative workup, intraoperative period, immediate postoperative period, and subsequent follow-up)?

How Do We Get There?

A secondary analysis of the raw data from the current study [1] seems likely to be able to answer several of the questions I’ve raised, and I would encourage the authors to see whether that is so. The contribution of each imaging modality to overall radiation exposure can be determined. Organ-specific exposure might be calculated by factoring in which body parts were specifically imaged. Finally, the time course of this exposure could be described. Alternatively, a single-center pilot study could prospectively gather these data. Study participants could be monitored longitudinally to determine whether actual cancer rates follow that predicted by current modeling.

From this point, a study could be conducted to measure the effectiveness of exposure-reducing techniques. For example, appropriate imaging protocols could be developed to reduce the number of images obtained in a standard series postoperatively. Oblique views may not be necessary when two orthogonal views could determine the degree of fracture healing. For the distal extremities, fluoroscopic imaging could be used to monitor for implant failure and loss of alignment. Alternative modalities for fracture surveillance could be used; for example, musculoskeletal ultrasound has been shown to be useful in the evaluation of long bone fractures of the distal extremities [3, 7, 10]. Relative decreases in exposure could be calculated while monitoring for adverse effects on postoperative complications and missed diagnoses.

A prospective, multicenter study could then be designed in which study participants who are matched for injury type, BMI, and other appropriate demographics are randomized between the current standard of care and alternative study protocols of interest. Total-body and organ-specific radiation exposures could be calculated and compared.

Although we do not look forward to another conflict in which our servicemembers sustain such high-energy trauma, we know it will happen. If that occurs, or when it does, it would be worth trying to repeat the current study after implementing lessons learned from these efforts.