A major milestone in eye cancer treatment was reached recently at TRIUMF. In the week of the 10th anniversary of treating its very first eye cancer patient, the TRIUMF cancer therapy facility treated its 100th patient on August 29. The only facility of its kind in Canada, the Proton Eye Treatment Facility was established in 1995 with a grant from the Mr. & Mrs. P.A. Woodward Foundation, and is operated in conjunction with the BC Cancer Agency, UBC Dept. of Ophthalmology and the Eye Care Centre at Vancouver General Hospital.
The facility treats a cancerous growth on the back of the eye called choroidal melanoma. Before proton treatment became available, the most common procedure was removal of the eye, or for smaller tumours, implanting a radioactive disk on the retinal wall under the tumour for a number of days.
“Proton therapy for eye tumours has allowed us to treat patients who would otherwise have required removal of the eye,” says UBC ophthalmologist Dr. Katherine Paton. “Frequently this preserves reasonable vision and function, and for patients with only one working eye this has been most gratifying.”
The treatment uses a low intensity beam of 74 MeV protons extracted from the TRIUMF cyclotron. The beam is modified by range modulation and collimation to provide a uniform dose over the volume of the tumour while sparing, if possible, the critical structures such as the lens and optic nerve. The tumour location is defined by tantalum clips that can be seen on an X-ray for beam alignment. The patient sits in a special treatment chair with the head immobilized in a mask and bite block and gazes at a blinking light during treatment. Because the beam of protons deposits its energy so predictably, it can successfully destroy a tumour while better preserving the other nearby parts of the eye. The painless treatment lasts about 90 seconds and patients are treated once a day for four consecutive days. Patients are referred to the facility from western Canada and prepared for treatment by specialists working at the Eye Care Centre at VGH in collaboration with oncologists and medical physicists from the BC Cancer Agency.
TRIUMF proton therapy coordinator, Ewart Blackmore observed that although TRIUMF is a basic research facility it has an enviable record in practical applications of its beams, particularly in the medical field.
The first patient treated was Mr. Lorne Scott of Campbell River, BC on August 21, 1995.