Does the Cancer Act 1939 really block new cancer treatments?

Claims that doctors, scientists, institutions or companies are hiding the truth are presented without sufficient evidence.

Even though the Cancer Act 1939 came into force long before the internet existed, it still sits at the centre of conspiracy theories on social media.

Posts claim that the law makes it illegal to talk about any cancer treatment other than chemotherapy, radiotherapy or surgery. Some go further and argue that the law prevents new treatments from being developed.

Yet the text of the law tells a very different story. We looked at what the Cancer Act 1939 actually says.

So what does the Cancer Act 1939 actually do?

In the mid-1930s, a cancer diagnosis in the UK meant facing a far bleaker outlook than it does today. Treatment options were limited, and chemotherapy did not yet exist.

In that climate, false and unsupported claims about supposed cancer cures could spread quickly from person to person. The Cancer Act 1939 was introduced in part to protect patients from people who sought to exploit their hope.

The law was passed in 1939, around a decade before the UK created the National Health Service, or NHS. For that reason, it also contained rules about how local authorities should provide treatment and other health services to people with cancer.

When the Act was first published, it had eight sections. It also covered legal questions such as the scope of the Act, how it should be interpreted, and which parts of the UK it applied to.

Today, every section apart from section 4 has either been repealed or incorporated into other legislation. Section 4 restricts the advertising of cancer treatments.

The law targets advertising, not cancer research

In its current form, the main purpose of the Cancer Act is to protect cancer patients and the wider public from a flood of advertisements for cancer treatments, regardless of who is behind them. The rules can apply to health professionals, pharmaceutical companies, alternative treatment practitioners and other individuals.

The word “advertisement” here involves a financial interest. In other words, the rule applies when a person or company sells a product, method or advice that they claim can treat cancer.

The law does not make a distinction based on who is selling the treatment. A pharmaceutical company, for example, cannot advertise a new cancer drug to the public in newspapers or on television. The law can also be used against websites that claim to treat tumours with “miracle cures.”

The Act contains some exemptions. Material that is intended for members of Parliament, local authorities, doctors, nurses, pharmacists and people who are training in those professions is not treated in the same way as advertising to the general public.

Technical publications for those groups can also fall outside the restriction. The same applies in some cases to notices from local authorities, voluntary hospitals or material that has approval from the Minister of Health.

It does not block new cancer treatments

One claim says the Cancer Act blocks potential cancer treatments that could be developed today.

But the law says nothing of the sort.

Nothing in the Act, which anyone can read online, prevents researchers from developing a new cancer treatment. Its purpose is to restrict cancer treatment advertising to the public, not cancer research itself.

Whether a treatment has been proven does not change that rule. Advertising chemotherapy, which is an established cancer treatment, to the public is also restricted.

Scientists continue to search for more effective cancer treatments, and international data show that survival has improved for many types of cancer in recent decades.

In the United States, the five-year survival rate across all cancers rose from 49 percent in the mid-1970s to 70 percent between 2015 and 2021.

A similar change can be seen in the United Kingdom. In the early 1970s, around one in four people with cancer survived for at least 10 years. Today, the figure is around one in two.

Those figures alone make it hard to argue that the Cancer Act 1939 has stopped progress in cancer research.

The UK government has made the same point in its responses to petitions that called for the law to be repealed:

“The 1939 Cancer Act does not prevent doctors offering any treatment option which is backed by robust evidence. The only surviving operative provision of the Act is Section 4, which is essentially a prohibition on taking part in “the publication of advertisements containing an offer to treat any person for cancer, or to prescribe any remedy thereof, or to give any advice in connection with the treatment thereof”. It is not directly relevant to this petition, since the provision doesn’t prohibit doctors from offering or advising on alternatives to chemotherapy. There appears to have been an incorrect interpretation. This provision prohibits advertising to the general public (except in situations outlined in sections 4(4) and 4(5) of the Act).”

Why these advertising rules exist

Cancer is a disease that can touch any of us. When someone you love is ill, you want to believe there is a treatment somewhere that might help.

In moments like that, it can be hard to weigh what is true and what is not. Even the smallest chance that something might work can feel like enough. You start thinking, what is the worst that could happen?

That vulnerability is exactly what people who sell fake treatments or remedies with no proven benefit can exploit.

Unproven treatment claims can put a patient’s health at risk. They can also cost patients time, motivation, and money.

One purpose of the UK Cancer Act is to reduce that risk.

And what about Turkey?

The picture in Turkey is a little more complicated.

Turkey does not have a separate law that regulates cancer advertising in the same way as the UK. However, a regulation that was revised in November 2025 prohibits direct and indirect advertising in health services.

Even health professionals cannot claim that practices with no scientific or clinical proof, or methods that have not become part of established medical practice, can treat a disease or help with treatment.

Turkey’s Advertising Board at the Ministry of Trade also takes action against product advertisements that make cancer-related health claims.

In 2025, for example, claims that a product was beneficial “in the prevention and treatment of cancer” were found to be scientifically unproven health claims that presented the product as if it were a medicine. The company received a monetary fine and was ordered to stop the advertisements.

In the same year, regulators also acted against content that featured a user who said a supplement had helped them “stop chemotherapy early.” The content was ordered to be removed, with access blocking as the next step if it remained online.

Having rules on the books does not mean that these claims disappear.

The Turkish Medical Association says that effective rules depend on continuous and transparent oversight.

Products and methods that still appear on social media with claims that they “cure cancer” are a reminder that enforcement matters just as much as the rules themselves.