Cancer Management and Research (Jan 2018)

Radiation-induced secondary malignancies for nasopharyngeal carcinoma: a pilot study of patients treated via IMRT or VMAT

  • Lee HF,
  • Lan JH,
  • Chao PJ,
  • Ting HM,
  • Chen HC,
  • Hsu HC,
  • Lee TF

Journal volume & issue
Vol. Volume 10
pp. 131 – 141

Abstract

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Hsiao-Fei Lee,1,2 Jen-Hong Lan,1,2 Pei-Ju Chao,1,2 Hui-Min Ting,1,2 Hui-Chun Chen,2 Hsuan-Chih Hsu,2 Tsair-Fwu Lee1–4 1Medical Physics and Informatics Laboratory of Electronics Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan, Republic of China; 2Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan, Republic of China; 3Graduate Institute of Clinical Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan, Republic of China; 4Department of Radiation Oncology, Kaohsiung Yuan’s General Hospital, Kaohsiung, Taiwan, Republic of China Background: Patients treated with radiotherapy are at risk of developing a second cancer during their lifetime, which can directly impact treatment decision-making and patient management. The aim of this study was to qualify and compare the secondary cancer risk (SCR) after intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in nasopharyngeal carcinoma (NPC) patients. Patients and methods: We analyzed the treatment plans of a cohort of 10 NPC patients originally treated with IMRT or VMAT. Dose distributions in these plans were used to calculate the organ equivalent dose (OED) with Schneider’s full model. Analyses were applied to the brain stem, spinal cord, oral cavity, pharynx, parotid glands, lung, mandible, healthy tissue, and planning target volume. Results: We observed that the OED-based risks of SCR were slightly higher for the oral cavity and mandible when VMAT was used. No significant difference was found in terms of the doses to other organs, including the brain stem, parotids, pharynx, submandibular gland, lung, spinal cord, and healthy tissue. In the NPC cohort, the lungs were the organs that were most sensitive to radiation-induced cancer. Conclusion: VMAT afforded superior results in terms of organ-at-risk-sparing compared with IMRT. Most OED-based second cancer risks for various organs were similar when VMAT and IMRT were employed, but the risks for the oral cavity and mandible were slightly higher when VMAT was used. Keywords: second cancer risk, organ equivalent dose, excess absolute risk, lifetime attributable risk, intensity modulated radiation therapy, volumetric modulated arc therapy

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