66. Clinical Study for Proton Beam Therapy

Takashi Nakano, Shinroku Morita, Shigeo Furukawa, Tatsuaki Kanai, Kouichi Shibayama, Takayoshi Ishii, Takeshi Hiraoka, Atsuko Abe, Tatsuya Ohono and Hirohiko Tsujii

Keywords: proton beam therapy, ocular melanoma

A marker ring made of titanium was modified for responsibility of positioning in proton beam therapy. We developed a eye melanoma simulation without marker ring operation and applied this method for one patient with small ocular melanoma. Instead of marker operation, a read particle was placed on the sclera with a sticky anesthetic drug. Position of the read particle was determined according to the vessel of conjunctiva bulba. CT image was taken for the eye with the read particle and treatment planning was done with reference to its position. Patient setup was done succcessfully with the read reference. This method is rather reliable and not expensive.

This year, 11 patients with ocular melanomas were treated with proton beam therapy. By March 1999, 74 patients with ocular melanoma had been treated with protons. Of these 73 were treated to a radical intent; 60 % of them were located contiguous to or involved in the optic disk or macula which are critical organs relating to complications. The 5-and 10-year survival rates were 95% and 89%, respectively. Both 5-and 10-year local control rates were 88%. The 5-year cumulative retention rate of the involved eye after treatment was 70 %. These results suggested that proton beam therapy for ocular melanoma is one of the better treatment modalities.

Preliminary experiment for carbon ion treatment for eye disease was started with rats this year. 60 rat eyes were exposed with 4Gy and 16Gy. Normal tissue response of the eye to carbon beams will be obtained by next year.

Two groups of 30 female Wister Rats (8 weeks old) were irradiated on their eyes with a single irradiation of carbon beams of 4 Gy and 16Gy. Carbon beams of SOBP of 2cm were used. The diameter of the beams was 13mm to encompass the entire eye. The end points for this study are as following;

Examination will be performed at 3 months, 6 months, and 1 year after irradiation.

Retina Early and late reactions
      Histological finding (H&E), Electron microscopy, Electron Retino Graphy
Cornea Early and late reactions
      Histological finding (H&E), Electron microscopy
Lens  cataract
      Slit lamp examination
Disk  Early and late reactions
      Histological finding (H&E), Electron microscopy

So far the 3 month examination after irradiation has been performed. At 3 months Apparent changes of Electron Retino Graphy were observed for eyes irradiated with 16 Gy. Slight changes of ERG were observed for eyes irradiated with 4Gy.