Real-time 4-D radiotherapy for lung cancer

Hiroki Shirato, Rikiya Onimaru, Masayori Ishikawa, Jun Ichi Kaneko, Tsuguhide Takeshima, Kenta Mochizuki, Shinichi Shimizu, Kikuo Umegaki

Research output: Contribution to journalReview articlepeer-review

41 Scopus citations


Respiratory motion considerably influences dose distribution, and thus clinical outcomes in radiotherapy for lung cancer. Breath holding, breath coaching, respiratory gating with external surrogates, and mathematical predicting models all have inevitable uncertainty due to the unpredictable variations of internal tumor motion. The amplitude of the same tumor can vary with standard deviations >5mm occurring in 23% of T1-2N0M0 non-small cell lung cancers. Residual motion varied 1-6mm (95th percentile) for the 40% duty cycle of respiratory gating with external surrogates. The 4-D computed tomography is vulnerable to problems relating to the external surrogates. Real-time 4-D radiotherapy (4DRT), where the temporal changes in anatomy during the delivery of radiotherapy are explicitly considered in real time, is emerging as a new method to reduce these known sources of uncertainty. Fluoroscopic, real-time tumor-tracking technology using internal fiducial markers near the tumor has ±2mm accuracy, and has achieved promising clinical results when used with X-ray therapy. Instantaneous irradiation based on real-time verification of internal fiducial markers is considered the minimal requisite for real-time 4DRT of lung cancers at present. Real-time tracking radiotherapy using gamma rays from positron emitters in tumors is in the preclinical research stage, but has been successful in experiments in small animals. Real-time tumor tracking via spot-scanning proton beam therapy has the capability to cure large lung cancers in motion, and is expected to be the next-generation real-time 4DRT.

Original languageEnglish (US)
Pages (from-to)1-6
Number of pages6
JournalCancer Science
Issue number1
StatePublished - Jan 2012

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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