Technology Transfer Bulletin, Vol 2, Issue 3 (May 1999)

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Technology Transfer Bulletin, Vol 2, Issue 3 (May 1999)

TRIUMF

Canada’s National Meson Facility

Technology Transfer Bulletin

MAY 1999

CANCER TREATMENT AT TRIUMF

For the past 4 years, TRIUMF has been the site of Canada’s only proton therapy unit that treats cancerous growths within the eye,

called ocular melanomas. There are about a dozen other similar facilities worldwide, and the cancer treatment program at TRIUMF

was made possible through a collaboration between the BC Cancer Agency, the University of British Columbia’s Eye Care Centre

and TRIUMF. The Mr. & Mrs. P.A. Woodward’s Foundation provided funds to construct the patient treatment chair and the proton

beam line equipment.

Before proton treatment became available at TRIUMF, the usual course of action for Canadian patients with large tumours or ones

at the back of the eye near the optic nerve was to remove the eye entirely. For smaller tumours, the preferred treatment is still

to implant a radioactive disk for a few days. Occasionally it is possible to remove small tumours surgically, but this can be

difficult. Any of these alternatives could damage other sensitive parts of the eye and result in some loss of vision. Proton therapy

offers the possibility of having the tumours stabilized, the eyes preserved, and depending on the

patient, the vision intact.

Eye Melanoma

Normal cells in the body divide and form new cells in an orderly and controlled manner throughout life

to replace worn out tissue, heal wounds and maintain healthy organs. When cells grow out of control,

they can form a mass known as a tumour. Benign tumours are those that grow and enlarge only at

the site where they begin. They do not spread to other parts of the body. Malignant tumours (cancer),

on the other hand, not only enlarge locally but also tend to invade and damage the nearby tissue and

organs, and spread to other parts of the body. This is called metastasis.

An ocular melanoma is a malignant tumour originating in the pigment-forming cells of the eye. The most common site is the

choroid layer, which is located between the sclera (white fibrous tissue of the outside of the eye) and retina (innermost layer).

Hence, the proper name is Choroidal or Uveal Melanoma. The outlook for local cure depends strongly on the size and growth

rate of the tumour. The 5-year local control rate (where the tumour is sterilized and incapable of further growth) is 95%, and the

5-year survival expectation is approximately 80%,

irrespective of the type of treatment received.

The Equipment and Treatment

Before treatment, a surgeon attaches three or four very small

metal disks to the eyeball, around the edges of the tumour.

These make the tumour edges visible in an X-ray picture

(taken just before the treatment, when the patient is already

positioned in the chair). This allows exact alignment of the

proton beam. The treatment team (a radiation oncologist, a

physicist and an ophthalmologist) calculates the best angle

of entry of the proton beam, to ensure maximum damage to

the tumour and minimum damage to the optic nerve and the

lens of the eye. The patient’s head is held still with a mask

and a bite block, both custom made. However, the eye itself

is not immobilized. To help the patient, the room lights are

turned off and the patient is asked to stare at a small flashing

light, which is positioned so that the protons enter the eye from the planned direction. The eye position is monitored using a TV

camera with large magnification. If motion is detected, the operator can quickly turn off the beam.


Following the development of a treatment plan, technicians test the treatment system to make sure that everything works properly.

The patient is now ready for treatment. He/she is aligned each day using the X-rays, and the proton beam is turned on for about

2 minutes. After four daily treatments, the tumour is incapable of further growth and will slowly regress.

TRIUMF’s main cyclotron can accelerate protons to speeds up to 3/4 the velocity of light and up to energies of 520 MeV. Proton

therapy, however, requires a slower-moving beam of protons to penetrate the depth of the eye. The optimum beam energy for eye

melanomas is found to be between 70 and 75 MeV.

Why Protons instead of Other Radiation?

Radiotherapy has been used for many years, but most of the treatments have been done with

X-rays (photons). X-rays are successful in destroying tumours but they also destroy healthy

tissue around the tumour. This is because the penetrating power of X-rays decreases

exponentially with increasing depth. This means that X-rays deposit most of their energy near

the surface of the body. If the tumour is deep-seated, this presents a problem.

Protons are particles that form part of the nucleus of every atom. Being particles, they are able

to slow down much faster than X-rays. Their power, however, does not decrease exponentially

like X-rays. Instead, they deposit more energy as they slow down, culminating in a peak. The

depth at which the peak occurs can be controlled by the amount of energy the protons are given

by the accelerator. They are also massive enough to stay on their directed path as they

penetrate into the eye, without being scattered into surrounding tissue. The proton beam can

be “modulated” so that it contains protons with a range of velocities. This means they will

deposit their tumour-destroying (kinetic) energy at different depths inside the tumour, since the

faster protons will penetrate a little deeper. Thus the entire tumour gets a uniform dose of

radiation, with a sharp fall-off at the edges and at the “downstream” end, and is sterilized with

minimal damage to other nearby parts of the eye.

Since 1977, proton

therapy has been used

successfully in other

countries. It is well

tested, and is the

preferred treatment for

medium sized tumours.

The first ever treatment

that was performed at

TRIUMF occurred in

August, 1995. Since

then, we have treated 50

patients. Before this,

Canadian patients had to

go abroad for proton

treatment. Now they can

receive it here at home,

and at a much lower cost.

CONFERENCES

TRIUMF hosts and organizes a number of conferences every year, usually between the Spring and Fall seasons. They are all

scientific or technical in nature but range from undergraduate to post-doctoral levels. Participants at these conferences come from

all over the world and the number of attendees range from 15 to over 1200 per conference. The number of attendee days for the

past year totalled 7724. It is through these conferences that TRIUMF has another impact on the economy of British Columbia,

and allows for one-on-one exchange of the latest ideas with scientists from around the globe, furthering the quality of Canadian

research as a whole.

VISITORS

On May 28, TRIUMF was pleased to host the French Ambassador from Ottawa, Mr. Denis Beauchard. He was accompanied by

the French Consul, Mr. Dejaeger and the French Scientific Attaché, Mr. Blamengin, both from Vancouver.

Mr. Ross Fitzpatrick, a B.C. federal Senator, accompanied by Ms. Pam McDonald from the Prime Minister’s Office and Ms.

Audrey Sojonky from B.C. minister, Mr. David Anderson’s office, also visited TRIUMF.

A NOTE OF THANKS

TJM Technical Centre, the research arm of MacMillan Bloedel, has recently donated various microwave equipment to TRIUMF.

TRIUMF staff have been working with TJM staff for many years, providing them with solutions to electronic and microwave issues.


We would like to take this opportunity to thank TJM for their generous contribution.

Technology Transfer at TRIUMF is funded by NRC and NSERC.

Technology Transfer Contacts: Philip L. Gardner Division Head, Technology Transfer, (604) 222-7436,

gardner@triumf.ca

Ann W. Fong

Questions and comments regarding this newsletter can be addressed to either of the above.

Technology Transfer Officer, (604) 222-7471, awoon@triumf.ca

For information on how to become part of TRIUMF’s supplier base please contact Andy Decsenyi, (604) 222-7416,

andyd@triumf.ca.

TRIUMF is operated as a joint venture of: Associate Members: TRIUMF

University of British Columbia University of Manitoba Carleton University 4004 Wesbrook

Mall

University of Victoria Université de Montréal Queen’s University Vancouver, BC

Simon Fraser University University of Regina V6T 2A3

University of Alberta University of Toronto Canada

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