Prognostic impact of average iodine density assessed by dual-energy spectral imaging for predicting lung tumor recurrence after stereotactic body radiotherapy

J Radiat Res. 2016 Jul;57(4):381-6. doi: 10.1093/jrr/rrv100. Epub 2016 Jan 28.

Abstract

The purpose of this study was to investigate the prognostic significance of average iodine density as assessed by dual-energy computed tomography (DE-CT) for lung tumors treated with stereotactic body radiotherapy (SBRT). From March 2011 to August 2014, 93 medically inoperable patients with 74 primary lung cancers and 19 lung metastases underwent DE-CT prior to SBRT of a total dose of 45-60 Gy in 5-10 fractions. Of these 93 patients, nine patients had two lung tumors. Thus, 102 lung tumors were included in this study. DE-CT was performed for pretreatment evaluation. Regions of interest were set for the entire tumor, and average iodine density was obtained using a dedicated imaging software and evaluated with regard to local control. The median follow-up period was 23.4 months (range, 1.5-54.5 months). The median value of the average iodine density was 1.86 mg/cm(3) (range, 0.40-9.27 mg/cm(3)). Two-year local control rates for the high and low average iodine density groups divided by the median value of the average iodine density were 96.9% and 75.7% (P = 0.006), respectively. Tumors with lower average iodine density showed a worse prognosis, possibly reflecting a hypoxic cell population in the tumor. The average iodine density exhibited a significant impact on local control. Our preliminary results indicate that iodine density evaluated using dual-energy spectral CT may be a useful, noninvasive and quantitative assessment of radio-resistance caused by presumably hypoxic cell populations in tumors.

Keywords: dual-energy CT; iodine density; lung cancer; oligometastases; stereotactic body radiotherapy.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Female
  • Humans
  • Iodine / chemistry*
  • Kaplan-Meier Estimate
  • Lung Neoplasms / diagnostic imaging*
  • Lung Neoplasms / radiotherapy*
  • Male
  • Middle Aged
  • Neoplasm Recurrence, Local / diagnosis*
  • Neoplasm Recurrence, Local / diagnostic imaging
  • Prognosis
  • Radiography, Dual-Energy Scanned Projection*
  • Radiosurgery*
  • Tomography, X-Ray Computed
  • Treatment Outcome

Substances

  • Iodine