International Journal of Radiation Oncology * Biology * Physics
Volume 64, Issue 2 , Pages 396-401, 1 February 2006

Outcomes of visual acuity in carbon ion radiotherapy: Analysis of dose–volume histograms and prognostic factors

  • Azusa Hasegawa, D.D.S., Ph.D.

      Affiliations

    • Hospital, Charged Particle Research Center, National Institute of Radiological Sciences, Chiba, Japan
    • Corresponding Author InformationReprint requests to: Azusa Hasegawa, D.D.S., Ph.D., Hospital, Charged Particle Research Center, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-8555, Japan. Tel: (+81) 43-251-2111; Fax: (+81) 43-256-6506
    • ,
  • Jun-etsu Mizoe, M.D., Ph.D.

      Affiliations

    • Hospital, Charged Particle Research Center, National Institute of Radiological Sciences, Chiba, Japan
    • ,
  • Atsushi Mizota, M.D., Ph.D.

      Affiliations

    • Department of Ophthalmology, Juntendo University Urayasu Hospital, Chiba, Japan
    • ,
  • Hirohiko Tsujii, M.D., Ph.D.

      Affiliations

    • Hospital, Charged Particle Research Center, National Institute of Radiological Sciences, Chiba, Japan

Received 7 June 2005; received in revised form 8 July 2005; accepted 8 July 2005. published online 26 September 2005.

Purpose: To analyze the tolerance dose for retention of visual acuity in patients with head-and-neck tumors treated with carbon ion radiotherapy.

Methods and Materials: From June 1994 to March 2000, 163 patients with tumors in the head and neck or skull base region were treated with carbon ion radiotherapy. Analysis was performed on 54 optic nerves (ONs) corresponding to 30 patients whose ONs had been included in the irradiated volume. These patients showed no evidence of visual impairment due to other factors and had a follow-up period of >4 years. All patients had been informed of the possibility of visual impairment before treatment. We evaluated the dose–complication probability and the prognostic factors for the retention of visual acuity in carbon ion radiotherapy, using dose–volume histograms and multivariate analysis.

Results: The median age of 30 patients (14 men, 16 women) was 57.2 years. Median prescribed total dose was 56.0 gray equivalents (GyE) at 3.0–4.0 GyE per fraction per day (range, 48–64 GyE; 16–18 fractions; 4–6 weeks). Of 54 ONs that were analyzed, 35 had been irradiated with <57 GyE (maximum dose [Dmax]) resulting in no visual loss. Conversely, 11 of the 19 ONs (58%) irradiated with >57 GyE (Dmax) suffered a decrease of visual acuity. In all of these cases, the ONs had been involved in the tumor before carbon ion radiotherapy. In the multivariate analysis, a dose of 20% of the volume of the ON (D20) was significantly associated with visual loss.

Conclusions: The occurrence of visual loss seems to be correlated with a delivery of >60 GyE to 20% of the volume of the ON.

Keywords:  Carbon ion radiotherapy , Optic nerve , Head-and-neck tumor , Late morbidity , Dose–complication probability model

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PII: S0360-3016(05)01170-3

doi:10.1016/j.ijrobp.2005.07.298

International Journal of Radiation Oncology * Biology * Physics
Volume 64, Issue 2 , Pages 396-401, 1 February 2006

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