A global drive to tackle the causes of cancer linked to lifestyle, such as alcohol abuse, sugar consumption and obesity, has been urged on Monday by the World Health Organisation as it predicted the number of new cases could soar 70% to nearly 25 million a year over the next 20 years.

Half of these cases are preventable, says the UN's public health arm in its World Cancer Report, because they are linked to lifestyle. It is implausible to think we can treat our way out of the disease, say the authors, arguing that the focus must now be on preventing new cases.

Even the richest countries will struggle to cope with the spiralling costs of treatment and care for patients, and the lower income countries, where numbers are expected to be highest, are ill-equipped for the burden to come.

The incidence of cancer globally has increased from 12.7m new cases in 2008 to 14.1m in 2012, when there were 8.2m deaths. By 2032, it is expected to hit almost 25m a year – a 70% increase.

The biggest burden will be in low- and middle-income countries, where the population is increasing and living longer. They are hit by two types of cancers – first, those triggered by infections, such as cervical cancers, which are still very prevalent in poorer countries that do not have screening, let alone the HPV vaccine.

Second, there are increasingly cancers associated with the lifestyles of more affluent countries "with increasing use of tobacco, consumption of alcohol and highly processed foods and lack of physical activity", writes Margaret Chan, WHO director general, in an introduction to the report.

Dr Christopher Wild, director of the International Agency for Research on Cancer (IARC) and joint author of the report, said when people know his job, they asked whether a cure for cancer had been found, yet few think about preventing the disease in the first place.

"Despite exciting advances, the report shows that we cannot treat our way out of the cancer problem. More commitment to prevention and early detection is desperately needed in order to complement improved treatments and address the alarming rise in the cancer burden globally."

His co-author, Dr Bernard Stewart from the University of New South Wales, talked of "the crucial role of prevention in combating the tidal wave of cancer" and called for discussion on how to encourage people to change their lifestyles, including a tax on sugared drinks, which could be one possible brake on cancers caused by obesity and lack of physical exercise.

The world had moved on from what Stewart called a "naive approach" to smoking, which causes lung and other cancers, and once was limited to handing out leaflets and haranguing people to give up. He cited the WHO global tobacco control treaty, which incentivises governments to pass laws banning smoking in public places.

The World Cancer Report, an 800-page volume on the state of cancer knowledge, which is the first for five years, must open up the debate, said Stewart.

"In relation to alcohol, for instance, we are all aware of the effects of being intoxicated but there is a burden of disease not talked about because it is not recognised," he said.

The report shows that alcohol-attributable cancers were responsible for a total of 337,400 deaths worldwide in 2010, mostly among men.

The majority were liver cancer deaths, but drinking alcohol is also a risk for cancers of the mouth, oesophagus, bowel, stomach, pancreas, breast and others.

"Labelling, availability and the price of alcohol should all be on the agenda," said Stewart.

So should taxation of sugar-sweetened drinks, he said. The report says efforts to reduce the percentage of fizzy drinks that contain substantial amounts of added sugar should become a high priority.

Stewart said that while obesity was a greater risk for diabetes than cancer, the the risk of the latter disease was likely to put more pressure on politicians to act because of the greater awareness of it in our communities.

About half of Britons do not recognise the importance of diet in protecting them against cancer, according to a poll carried out by the World Cancer Research Fund. Eating a lot of red meat – especially processed – increases the risk of bowel cancer.

Eating fruit and vegetables may protect against some forms of cancer, although the World Cancer Report says it "does not appear to be as strongly protective against cancer as initially believed". However, IARC says it is definitely protective against diabetes and heart disease.

The survey also found that 59% of people did not know that putting on weight increased cancer risk.

Lung cancer is the most commonly diagnosed form of the disease among men (16.7% of cases) and the biggest killer (23.6% of deaths), says the IARC report. Breast cancer is the most common diagnosis in women (25.2%) and caused 14.7% of deaths, which is a drop and now only just exceeds lung cancer deaths in women (13.8%). Bowel, prostate and stomach cancer are the other most common diagnoses.

Jean King, Cancer Research UK's director of tobacco control, said: "People can cut their risk of cancer by making healthy lifestyle choices, but it's important to remember that the government and society are also responsible for creating an environment that supports healthy lifestyles. It's clear that if we don't act now to curb the number of people getting cancer, we will be at the heart of a global crisis in cancer care within the next two decades."