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1951: Debut of the cobalt bomb

The Story


Cancer is second only to heart disease as a cause of death in Canada. On Oct. 27, 1951, a Canadian invention revolutionizes cancer treatment. CBC Radio describes how it works: a patient in a plaster cast is wheeled into a room in Victoria Hospital in London, Ont. One end of a large metal cylinder is positioned over her body. Everyone leaves the room. Outside, a technician presses a button. A powerful dose of radiation surges deep into the patient's body, destroying cancerous cells. The Canadian cobalt bomb therapy unit has made its world debut.

Medium: Radio
Program: CBC News Roundup
Broadcast Date: Oct. 27, 1951
Reporter: John Trethewey
Duration: 2:19

Did You know?


• Cobalt therapy revolutionized cancer radiation treatment throughout the world but was popularized under the rather unfortunate name, "Cobalt Bomb."

• The London unit wasn't the only one in Canada. Saskatoon's University Hospital treated a patient with a similar machine a few days later, and had actually built theirs first. Canada had two machines; no other country had anything similar.

• The cobalt-60 radioactive isotope was a new and unique Canadian resource. After the Second World War, National Research Council scientists had identified cobalt-60 as a radiation source particularly suitable for cancer therapy. A unique heavy water reactor production facility opened at Chalk River in 1947, providing scientists with ample quantities of the highly radioactive cobalt-60 for testing.

• Cobalt-60 was much cheaper, safer, and more powerful than the radium used in then-conventional therapeutic x-rays. (The cost of the entire unit was $50,000; the amount of radium needed would have been $50 million.) And deep-seated tumours needed to be treated by beaming radiation into the body. Cobalt-60 was well-suited to this method. But what was still needed was a special machine to beam cobalt-60 in a controlled, calibrated way.

• By 1949, two cooperative but independent projects were underway. One was in Ottawa, by Eldorado Mining and Refining. The Saskatchewan Cancer Institute launched another at the University of Saskatchewan in Saskatoon. Both had completed prototypes by summer 1951, and were testing in concrete-shielded rooms in London and Saskatoon. The Eldorado cobalt bomb treated its first patient on Oct. 27, the Saskatchewan machine on Nov. 8.

• The cure rate for cervical cancer soon climbed from 25 per cent to 75 per cent. In the '40s, only one in five patients survived for five years after getting cancer. In 2002, because of improved treatments, one in two lives at least that long.

• The cobalt bomb is the grandfather of all radiation therapy units in modern cancer facilities today. An estimated 7 million people around the world have benefited from cobalt-60 therapy.

• University of Saskatchewan medical physicist Harold Johns (1915-1998), who developed the cobalt-60 cancer therapy unit in Saskatchewan, received honours from the Canadian Science and Engineering Hall of Fame (1998), Canadian Cancer Society (1982) and Canadian Medical Hall of Fame (1998). He was made an Officer of the Order of Canada in 1977 for his contributions to medical science.

• While other cancer treatment technologies replaced cobalt-60 radiotherapy after 1965, the Canadian design is still so simple and trouble-free that it continues to be used in other countries today.


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