Lifetime Achievement: Dr. Harold Johns
Dr, Harold Johns
(Illustration by Irma Coucill, courtesy of the Canadian Medical Hall of Fame in London, Ontario)
In previous issues, Portal’s Lifetime Achievement section has featured senior scientists who are still leading figures in Ontario’s cancer research community. Starting in this issue, we turn our attention to earlier generations of cancer researchers. We will continue to profile Ontario’s active researchers through news articles and special features.
In the 1950s, Maclean’s magazine remarked it was ironic that a new Canadian invention designed to treat cancer was being dubbed the “cobalt bomb.” Fifty years later the nickname is still ironic, but there is also a ring of truth to it: by inventing a treatment that is credited with saving millions of lives, Dr. Harold Johns really did drop a bomb – on cancer.
Radiation has been used to treat cancer since the 1890s. However, before Johns’ invention, most radiation was generated by vacuum x-ray tubes that produced relatively low energy x-rays. The energy from these rays was deposited close to the skin, where they can cause serious complications.
Scientists hypothesized that higher-energy x-rays would probably produce better results. If the energy was deposited deeper in the body, it would kill more cancer cells and damage fewer healthy cells. But before Johns, there was little progress on how to generate these high-energy rays.
Johns proposed that a radioactive isotope called cobalt 60 could be used. He worked with Atomic Energy of Canada Limited to produce enough cobalt 60 to generate the rays and collaborated with other Canadian researchers to design a machine that could beam them into patients’ bodies.
Johns was also involved with building a prototype of the machine at the University of Saskatchewan. A second prototype was built in Ottawa using the same technology Johns had proposed. The Ottawa machine was completed first and delivered the first treatment on October 27, 1951. The Saskatchewan machine was operational less than two weeks later, delivering its first treatment on November 8.
For some cancers, the effect of introducing cobalt 60 treatment worldwide really was like dropping a bomb. The percentage of patients who died within five years of being diagnosed with cervical cancer plummeted from over 75 per cent to 25 per cent. Cure rates for many other cancers also improved dramatically.
The revolution in radiation therapy inspired other scientists to make further advances. After 1965 the cobalt 60 treatment was replaced in Canada by newer technologies, but the Canadian design did not become obsolete. Noted for its simplicity and functionality, the design is used in less-developed countries where newer technologies would be difficult to support.
Using physics to solve problems in medicine was Johns’ life work. Born in Chengdu, China in 1915, Johns was educated at McMaster University and the University of Toronto. In 1956, five years after inventing cobalt 60 treatment, Johns re-located to Ontario and became a professor at the University of Toronto.
Johns was influential in the early development of CT scanners and the definition of mammographic imaging. He also did significant work in showing the DNA damage in cells exposed to ultraviolet rays. His book, The Physics of Radiology, is a classic text of the early era of medical physics.
In Ontario, Johns is remembered as a builder of the province’s medical research community. A founder of the Department of Medical Biophysics at the University of Toronto, Johns recruited and trained some of the most celebrated scientists in Canadian history.
An officer of the Order of Canada, Johns was awarded the Queen’s Jubilee Medal, the Gairdner International Award and the Medal of Honour of the Canadian Medical Association. Each year, the National Cancer Institute of Canada presents the Harold E. Johns Award to a leading Canadian biomedical researcher.
When Johns was inducted into the Canadian Medical Hall of Fame in 1998, his citation noted the “cobalt bomb” had been used to treat seven million patients, and saved many of their lives. In other words, the builder of Canada’s most famous “bomb” has saved more lives than almost any other Canadian, past or present.
