Letter to the Editor: Steroid use in anterior cervical discectomy and fusion

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  • Oregon Health & Science University, Portland, OR
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TO THE EDITOR: I read with interest the article by Jeyamohan et al.5 (Jeyamohan SB, Kenning TJ, Petronis KA, et al: Effect of steroid use in anterior cervical discectomy and fusion: a randomized controlled trial. J Neurosurg Spine 23:137–143, August 2015). The study was well conducted, and the conclusions were of interest to many. However, I am concerned about a protocol that required 3 fine-cut CT scans of the cervical spine at 6, 12, and 24 months after surgery for fusion assessment in a group of patients averaging 54 years of age. Computed tomography scanning has long been considered the gold standard in assessing the results of arthrodesis (see, for example, Siambanes and Mather, 19989); however, recent data on the potential harm from CT-related ionizing radiation has added an element of caution to the routine use of CT imaging, especially in children (see Table 2 and Fig. 2 in Hikino and Yamamoto, 20154).2,6,7 The Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation promulgated a significant linear, no-threshold dose-response relationship between ionizing radiation dose and the development of cancer in humans, based in part on data from Japanese atomic bomb survivors.3 It has been estimated that 29,000 future cancers might be attributed to CT scans performed in the United States in 2007.2

A cervical spine CT is estimated to expose a patient to 4 mSv of radiation.10 According to one assessment, a routine neck CT in a 40-year-old patient would cause 1 radiation-induced cancer in 4430 female or 6058 male patients (see Table 4 in Smith-Bindman et al., 200910). In those 60 years of age, the estimated risk was reduced to 1 case in 6700 female or 8030 male patients. Accordingly, 3 cervical CT scans would raise the risk for any cancer to 1477 females or 2019 males at 40 years of age. Some have questioned even the routine use of postoperative radiographs in post–anterior cervical fusion patients whose clinical course is unremarkable.1 To spare patients unnecessary radiation exposure, CT or flexion-extension radiographs have been utilized only if clinical symptoms or radiographs were suggestive of pseudarthrosis.

As regards cervical spine CT in children, one report8 described a risk of excess thyroid cancers ranging from 1 to 33 cases per 10,000 CT scans in females or 1 to 6 cases for 10,000 CT scans in males. In another recent report,4 the thyroid cancer estimate was as high as 100 cancer cases in males or 700 cancer cases in females per 100,000 scans. At the high end of the estimate in the article by Schonfeld et al.,8 3 cervical CT scans might increase the incidence of thyroid cancer in younger patients to 100 cases per 10,000 scans. This would imply that 1 or more of the 112 patients in the study by Jeyamohan et al.5 might suffer a thyroid cancer as a result of participating in that study. In the Hikino et al. report,4 there could be as many as 2 new cases per 100 female patients undergoing 3 cervical CT studies. These authors asserted that “limiting neck CT scanning to a higher-risk group would increase the gap between benefit and harm, whereas performing CT routinely on low-risk cases approaches a point where its harm equals or exceeds its benefit.” This statement probably applies to adult patients as well.

Radiation doses, visceral exposures, and potential lifetime cancer risks are much higher for abdominal CTs and therefore, presumably, for lumbar CTs.10 These data suggest that performing CT in every spinal fusion patient should no longer be the gold standard to ascertain whether bony fusion has occurred. Such scanning should be reserved for those patients with clinical problems suggesting that pseudarthrosis may be present and requires attention. The continuing insistence of clinical studies and article peer reviewers that CT scans are needed to prove arthrodesis should be relaxed to spare patients unnecessary radiation exposure.

References

  • 1

    Bartels RHMA, , Beems T, , Schutte PJ, & Verbeek ALM: The rationale of postoperative radiographs after cervical anterior discectomy with stand-alone cage for radicular pain. J Neurosurg Spine 12:275279, 2010

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  • 2

    Berrington de González A: Projected cancer risks from computed tomographic scans performed in the United States in 2007. Arch Intern Med 169:20712077, 2009

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  • 3

    Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation: Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2(2006) Washington, DC, The National Academies Press, 2006

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  • 4

    Hikino K, & Yamamoto LG: The benefit of neck computed tomography compared with its harm (risk of cancer). J Trauma Acute Care Surg 78:126131, 2015

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  • 5

    Jeyamohan SB, , Kenning TJ, , Petronis KA, , Feustel PJ, , Drazin D, & DiRisio DJ: Effect of steroid use in anterior cervical discectomy and fusion: a randomized controlled trial. J Neurosurg Spine 23:137143, 2015

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  • 6

    Mazonakis M, , Tzedakis A, , Damilakis J, & Gourtsoyiannis N: Thyroid dose from common head and neck CT examinations in children: is there an excess risk for thyroid cancer induction?. Eur Radiol 17:13521357, 2007

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  • 7

    Muchow RD, , Egan KR, , Peppler WW, & Anderson PA: Theoretical increase of thyroid cancer induction from cervical spine multidetector computed tomography in pediatric trauma patients. J Trauma Acute Care Surg 72:403409, 2012

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  • 8

    Schonfeld SJ, , Lee C, & Berrington de González A: Medical exposure to radiation and thyroid cancer. Clin Oncol (R Coll Radiol) 23:244250, 2011

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  • 9

    Siambanes D, & Mather S: Comparison of plain radiographs and CT scans in instrumented posterior lumbar interbody fusion. Orthopedics 21:165167, 1998

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  • 10

    Smith-Bindman R, , Lipson J, , Marcus R, , Kim KP, , Mahesh M, & Gould R, : Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch Intern Med 169:20782086, 2009

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Disclosures

The author reports no conflict of interest.

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  • Albany Medical College, Albany, NY
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Response

We very much appreciate the concern with regard to obtaining 3 postoperative CT scans and the increased risk of radiation-induced cancers in the study population. The effects of gamma radiation have been studied in large populations (Hiroshima, Chernobyl), and the link to certain cancers has been well established. Though the chromosomal damage caused by beta radiation (CT scanners and radiographs) may be greater than that by gamma radiation, the method of administration to small regions of the body, with lower doses separated by greater periods of time, probably mitigates some of these risks.1 In fact, no direct data link radiographs to cancer in the adult population, probably because of the impracticality of performing such a study. An indirect analysis by Smith-Bindman et al. revealed that performing CT scanning of the head and neck will induce 1 additional cancer in 4430 females in the 40-year-old age group;3 however, this finding is based on multiple assumptions. The authors readily acknowledge some of the weaknesses of their study: the radiation dosages varied significantly; they were unaware of actual absorbed radiation; and they could have improperly estimated the lifespan of the study population, which would have a significant statistical effect in predicting cancer rates.

We acknowledge that we subjected our patients to risks when obtaining CT scans, but we do object to the statement that we may have caused 1 or 2 cancers by conducting the study. This prediction was based on a study by Schonfeld et al., who looked at cancer rates in the pediatric population.2 It is well known that CT scanning in infants carries a greater risk of causing cancers later in life. With regard to thyroid cancer specifically, there is an inverse relationship between age and radiation-related cancer risk. We had no pediatric patients in our study. Therefore, the statement that we caused 1 or 2 cancers simply has no foundation.

Studies are performed to answer questions and to change our practice patterns for the good of our patients. Most medical studies have risks, and many times those risks are not completely understood at the time of study inception. Some risks may be quite significant, and for that reason, we have institutional review boards and an extensive consent process for the protection of patients. Would the study have been accepted for presentation and/or publication without the CT data? I do not know, but I doubt it since we were wondering if fusion rates were altered by dexamethasone administration. Certainly, we hope that the publication of our study will help many, with no harm to our study subjects.

References

  • 1

    Berrington de González A: Projected cancer risks from computed tomographic scans performed in the United States in 2007. Arch Intern Med 169:20712077, 2009

    • Search Google Scholar
    • Export Citation
  • 2

    Schonfeld SJ, , Lee C, & Berrington de González A: Medical exposure to radiation and thyroid cancer. Clin Oncol (R Coll Radiol) 23:244250, 2011

    • Search Google Scholar
    • Export Citation
  • 3

    Smith-Bindman R, , Lipson J, , Marcus R, , Kim K, , Mahesh M, & Gould R, : Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch Intern Med 169:20782086, 2009

    • Search Google Scholar
    • Export Citation

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Contributor Notes

INCLUDE WHEN CITING Published online February 26, 2016; DOI: 10.3171/2015.9.SPINE151052.

  • 1

    Bartels RHMA, , Beems T, , Schutte PJ, & Verbeek ALM: The rationale of postoperative radiographs after cervical anterior discectomy with stand-alone cage for radicular pain. J Neurosurg Spine 12:275279, 2010

    • Search Google Scholar
    • Export Citation
  • 2

    Berrington de González A: Projected cancer risks from computed tomographic scans performed in the United States in 2007. Arch Intern Med 169:20712077, 2009

    • Search Google Scholar
    • Export Citation
  • 3

    Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation: Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2(2006) Washington, DC, The National Academies Press, 2006

    • Search Google Scholar
    • Export Citation
  • 4

    Hikino K, & Yamamoto LG: The benefit of neck computed tomography compared with its harm (risk of cancer). J Trauma Acute Care Surg 78:126131, 2015

    • Search Google Scholar
    • Export Citation
  • 5

    Jeyamohan SB, , Kenning TJ, , Petronis KA, , Feustel PJ, , Drazin D, & DiRisio DJ: Effect of steroid use in anterior cervical discectomy and fusion: a randomized controlled trial. J Neurosurg Spine 23:137143, 2015

    • Search Google Scholar
    • Export Citation
  • 6

    Mazonakis M, , Tzedakis A, , Damilakis J, & Gourtsoyiannis N: Thyroid dose from common head and neck CT examinations in children: is there an excess risk for thyroid cancer induction?. Eur Radiol 17:13521357, 2007

    • Search Google Scholar
    • Export Citation
  • 7

    Muchow RD, , Egan KR, , Peppler WW, & Anderson PA: Theoretical increase of thyroid cancer induction from cervical spine multidetector computed tomography in pediatric trauma patients. J Trauma Acute Care Surg 72:403409, 2012

    • Search Google Scholar
    • Export Citation
  • 8

    Schonfeld SJ, , Lee C, & Berrington de González A: Medical exposure to radiation and thyroid cancer. Clin Oncol (R Coll Radiol) 23:244250, 2011

    • Search Google Scholar
    • Export Citation
  • 9

    Siambanes D, & Mather S: Comparison of plain radiographs and CT scans in instrumented posterior lumbar interbody fusion. Orthopedics 21:165167, 1998

    • Search Google Scholar
    • Export Citation
  • 10

    Smith-Bindman R, , Lipson J, , Marcus R, , Kim KP, , Mahesh M, & Gould R, : Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch Intern Med 169:20782086, 2009

    • Search Google Scholar
    • Export Citation
  • 1

    Berrington de González A: Projected cancer risks from computed tomographic scans performed in the United States in 2007. Arch Intern Med 169:20712077, 2009

    • Search Google Scholar
    • Export Citation
  • 2

    Schonfeld SJ, , Lee C, & Berrington de González A: Medical exposure to radiation and thyroid cancer. Clin Oncol (R Coll Radiol) 23:244250, 2011

    • Search Google Scholar
    • Export Citation
  • 3

    Smith-Bindman R, , Lipson J, , Marcus R, , Kim K, , Mahesh M, & Gould R, : Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch Intern Med 169:20782086, 2009

    • Search Google Scholar
    • Export Citation

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