This Week in History


A "Bomb" in the Fight Against Cancer!

For the week of Monday October 21, 2002

On October 27, 1951, at the London Regional Cancer Centre in London, Ontario, cobalt-60 radiation therapy was first used on a cancer patient. The development of this new treatment by Canadian scientists was an important step in the battle against cancer.

Model demonstrating cobalt-60<br>teletherapy unit

Model demonstrating cobalt-60"
teletherapy unit

© LAC / PA111543

At the end of the 1940s, with cancer rates increasing worldwide, two teams of Canadian researchers, one in Saskatoon, Saskatchewan, and the other in London, Ontario, set out to develop a new treatment for the disease. The current technology used gamma rays from the naturally radioactive element radium to kill tumours, but radium was very expensive, worked best on small, superficial tumors and required long treatments to be effective.

Cobalt-60, a radioactive isotope of the metal cobalt, was proposed as an alternative to radium, since it was cheaper and more powerful. Canada’s nuclear laboratory at Chalk River, Ontario, was one of the few places worldwide capable of producing large quantities of cobalt-60. However, before it could be used to treat cancer, a machine was needed to contain the highly radioactive material and focus its rays precisely on tumours deep within the body.

The task of the Saskatoon and London teams was to develop such a device. Working separately, yet co-operatively, the teams exchanged ideas on problems, performance requirements and design aspects. On August 18, 1951, the Saskatoon team, led by physicist Harold E. Johns and composed of physics graduate students from the University of Saskatchewan, completed the first cobalt-60 teletherapy unit. Two months later, the London team of engineers from the Eldorado Mining and Refining Company, doctors from London’s Victoria General Hospital and researchers from the University of Western Ontario, became the first to treat a cancer patient. While slightly different, both teams’ designs were successful.

A plant worker is putting on shoes to protect<br>against radioactivity, Chalk River, Ont<

A plant worker is putting on shoes to protect
against radioactivity, Chalk River, Ont.

© LAC / PA-111377

Misleadingly nicknamed the “cobalt bomb” because of its positive medical use of atomic energy as compared to the atomic bomb, the cobalt-60 teletherapy unit improved cancer treatment worldwide. These units were not only more compact and more effective at treating deep-seated tumours than previous radiotherapy devices, but they were also 6000 times cheaper! Between 1951 and 1971, Atomic Energy of Canada Ltd. sold 965 cobalt-60 machines to 53 countries.

New technologies largely replaced cobalt-60 teletherapy units after 1965, but some countries still use them today. The Development of the Cobalt-60 Beam Therapy Unit in Canada is recognized as an event of national historic significance.

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