It appears a primary excuse used for the introduction of the The Cancer Act of 1939 in the United Kingdom was to ‘Protect the public from Quackery and Charlatans,’ but hindsight tells a different story. Taking into consideration what truths have come to light we see not one reason for this action but two.
One; was to ensure that all types of cancers were to be treated by the "Radium-Based" methods (Cancer Inducing Radiation) and,
Second; it was necessary to introduce such an act to protect the profits of Pharmaceutical companies.
The following 2 links will provide you with the Cancer Act of 1939 for your own review.
What has now been proven is:
"But nobody today can say that one does not know what cancer and its prime cause be. On the contrary, there is no disease whose prime cause is better known, so that today ignorance is no longer an excuse that one cannot do more about prevention. That prevention of cancer will come there is no doubt, for man wishes to survive. But how long prevention will be avoided depends on how long the prophets of agnosticism will succeed in inhibiting the application of scientific knowledge in the cancer field. In the meantime, millions of men must die of cancer unnecessarily." ~ Nobel Prize Winner Otto Warburg in a meeting of Nobel Laureates, June 30, 1966