Cancer became the top killer of Canadians in 2011, yet people are often living longer after being diagnosed.

Curing cancer often leads the most hoped-for list when you ask people what medical breakthroughs they would like to see.

But trying to answer the question of whether the war on cancer is being won means stepping into a contradictory tangle of statistics, anecdotes, hopes and fears.

In 1971, U.S. President Richard Nixon declared the 'war on cancer' in the annual state of the union address.

Measuring progress in the fight depends on who you ask and how success is measured.

There has been remarkable progress against some childhood cancers but very little change in mortality rates for some other forms.

Clifton Leaf, author of an article in Fortune magazine called "Why We're Losing the War On Cancer," is one of the beneficiaries of the success against certain cancers affecting children. Leaf had Hodgkin's disease, a cancer of the lymph system, in the 1970s — a decade when he said most of the total survival gains against cancer occurred.

Leaf focuses on actual death rates, which haven't budged much in decades for the diseases that tend to be the hardest to treat: lung cancer, pancreatic cancer, liver cancer.

The number of people getting cancer and dying of it keeps going up, says childhood cancer survivor Clifton Leaf. (Courtesy Clifton Leaf) "That's why I look at the raw numbers, because it keeps us honest," said Leaf. "If we keep looking at the number of people getting this disease and dying of it, we will see that those numbers keep going up."

"I hate to say that I don't think there will be a cure, considering I'm sitting here, cured of cancer," Leaf said.

Leaf added "there will not be one cancer magic bullet."

That's partly because there are 200 or more forms of cancer.

"We shouldn't neglect the fact that cancer is a very complicated and complex disease," said Dr. Ben Neel, director of the Ontario Cancer Institute at Toronto's Princess Margaret Hospital.

"Even lung cancer is probably 10 different types of molecular disease."

For Neel, it's not realistic to expect to wake up one morning and read newspaper headlines proclaiming "Cancer Cured."

"I often say that cancer will not end with a bang but with a whimper."

Dr. Ben Neel believes cancer will end with a whimper not a bang. (CBC) Neel predicted there will be continued progress against subsets of disease, such as HER-2 positive breast cancer or chronic myelogenous leukemia or CML — two existing success stories.

The biological basis of cancer also makes a single silver bullet less likely to work.

"The first factor of risk to develop cancer is aging," said Mario Chevrette, who studies prostate and kidney cancer at McGill University in Montreal.

"Sooner or later, we will have cancers in our body."

And when we do, the mutated genes in each person's type of cancer will differ. And even when a cancer treatment works, in many cases cancer cells adapt and develop resistance.

Prevention to cut cancer rates in half

Both Leaf and Neel stressed that to win the war against cancer, it needs to be fought on all fronts, including prevention.

"If the public were just to adopt what we already know, cancer rates should be halved," Neel noted.

He said cancer incidence rates could be cut in half through these preventive steps:

Quitting smoking: 25 per cent to 30 per cent of cancers are caused by smoking, but a quarter of the population still smokes.

Avoiding drinking alcohol in excess.

Tackling obesity.

Increasing physical activity.

Fighting infectious agents: HPV causes some vaccine-preventable forms of cervical cancer, H. pylori bacteria cause stomach cancer and hepatitis B virus is a major cause of liver cancer that can be prevented with vaccination.

An area of cancer research that didn't deliver the expected short-term results now seems more promising — using the body's own immune system to do the fighting.

Tumour-fighting soldiers

Immunotherapy was hyped by the media in the1970s and then largely forgotten by the public. Researchers studying ways to use the body's own immune system to fight cancer have continued their work.

Scientist Pamela Ohashi at Princess Margaret Hospital in Toronto is one of them. This spring, Ohashi said she and her colleagues hope to start a study on patients. It would be a first in Canada that uses some of the immune system's T-cells to fight cancer.

T-cells are a type of white blood cells that have the ability to specifically recognize a target, such as a flu virus.

In Ohashi's study, the T-cells, called tumour specific lymphocytes, come from a patient's own tumour. The experimental approach first treats patients with drugs to deplete their blood cells to give the tumour specific T-cells more room and nutrients to do their job.

Then the patient's own T-cells are reinjected.

"It's almost like a war," Ohashi said. "In a sense, these T-cells are like the soldiers. You just need a lot of them to go on and fight the tumour."

Pamela Ohashi said she's tempted to call an experimental immune therapy against melanoma a cure. (CBC) When the approach was tried in the U.S. against deadly melanoma, the results were remarkable, Ohashi said.

"I think everybody's scared to use this cure word," she said. "There are patients living six, seven years still disease-free that should not have lived for six years. I would be tempted to call that a cure. We'll see."

As a palliative care physician at Toronto General Hospital, Dr. James Downar isn't as focused on trying to extend the life of people with cancer. Instead, Downar works on making that person's quality of life as high as possible.

Unrealistic hope

"Unfortunately, our success in reducing the mortality from cancer over the past 60 years has been very, very modest," said Downar. "So I don't think, as I say, that it's realistic or even necessary to talk about curing cancer in order to make a big impact."

He sees some downside in promoting unrealistic hope from a cure or positive prognosis for some patients with terminal cancer.

"We know that patients who expect to have a good outcome, patients who are expecting to have a long prognosis will request different types of therapies than patients who are expecting a poorer outcome."

Patients may request more aggressive therapies that may not actually be helping them, Downar said.

"We have seen over the past decade that more and more patients with cancer are dying in the ICU than dying while receiving chemotherapy, going to the emergency room and spending hours and hours on a stretcher in the final month in their life."

These are choices thousands of Canadians face each year, with an estimated 177,800 new cases of cancer expected to be diagnosed annually.

This week CBC News reports on the search for cures for aging, Type 1 diabetes, the common cold, obesity and cancer on CBC Radio One, CBC News Network, The National and at cbc.ca/news/health/.