CBC MARKETPLACE: HEALTH » CANCER
Key cancer questions in the chase for answers
Broadcast: March 5, 2006

What causes cancer?
Cancer occurs when cells are triggered to grow abnormally. Triggers include genetics, radiation, and carcinogens.

Are cancer rates really up, or are they just climbing with our aging population?
Some explain rising cancer rates as a natural outcome of our aging population; rates have increased in some elderly-onset forms of cancer. But the rates are increasing at remarkable rates among other age groups too. For instance, childhood cancers have risen over 20 per cent in 30 years.

Meanwhile, prostate cancer, non-Hodgkin's lymphoma, thyroid and testicular cancers are all increasing. All have links to environmental contaminants.

According to the Canadian Cancer Society, over six million people die of cancer worldwide each year. The problem will be 50 per cent greater by 2020.

Over the next 30 years, the Canadian Strategy for Cancer Control estimates:

• Almost 6 million Canadians will be diagnosed with cancer
• About 3 million will die from cancer
• Direct cancer healthcare costs will be more than $176 billion
• Over $248 billion in tax revenues will be lost because of disability due to cancer

What is a carcinogen?
A carcinogen is a chemical known or believed to cause cancer in humans. The number of proven carcinogens is comparatively small, but many more chemicals are suspected to be carcinogenic.

Why are some products labelled and others not?
The packaging and labelling regulations for consumer chemicals products in Canada is the Consumer Chemical and Container Regulations CCCR (2001), which is found in the Hazardous Products Act.

In November 2006, labels on cosmetic products will have to list their ingredients – something that isn't currently required.

For nearly two years, Mae Burrows, executive director of the Labour Environmental Alliance Society, has been fighting for warning labels about carcinogens on products. Health Canada is now in talks with various stakeholders (including Burrows and product manufacturers) about updating labelling rules.

In the meantime, Burrows would like companies to at least inform consumers when their products contain a possible human carcinogen, something that isn't currently required.

For instance, there is currently no regulation requiring the listing of ingredients, including known carcinogens, on consumer cleaning product labels (although products that include ingredients deemed "hazardous" are required to display the "hazard symbol").

Isn't it proven that a healthy diet prevents cancer?
No. For example, a low-fat diet used to be touted as a cancer-fighter. Recent studies cast that into doubt.

The research found that women who switched to a low-fat diet later in life did not see a reduced risk of breast cancer, colorectal cancer or heart disease.

For eight years, researchers in the U.S. conducted three separate studies of 48,835 women with an average age of 62 who were randomly chosen to adopt either a low-fat diet or keep eating as normal.

Simply cutting the total fat in the diet generally didn't help reduce the risk of cancer or heart disease among these women, according to the studies, which were published in the Feb. 8, 2006, issue of the Journal of the American Medical Association.

Changing diet after age 50 may not work as well as eating healthy foods earlier in life, said Mara Vitolins, a dietician who co-authored one of the papers.

But researchers say older women shouldn't give up trying to eat healthy. They say the focus should be on reducing saturated fats and trans fats found in processed foods, meat and some dairy products.

Participants in the study filled out food questionnaires but the research did not account for types of fat, and the women may not have reduced their intake by enough to see a difference, the researchers added.

Cancer can also take years to develop. While women in the low-fat group did not show a reduction in cancer incidence overall, there was a small decrease in polyps that are precursor to colon cancer.

Meanwhile, the cancer-fighting benefits of a high-fibre diet have also been called into question. A review published in December 2005 found that eating a diet high in fibre does not reduce the risk of colorectal cancer.

The idea that fibre may protect against colon cancer is based on the notion that the foods help keep us regular. By bulking up stool, it was thought that insoluble fibre like wheat bran helps waste move through faster, diluting carcinogens in the bowel.

But proof that dietary fibre from fruits and vegetables, cereals or bran reduces the risk of colon cancer has been elusive, with animal studies, population studies and randomized clinical trials showing inconsistent results.

The latest study, published in the Dec. 14 issue of the Journal of the American Medical Association, analyzed data from 13 international trials involving more than 725,000 men and women who were followed for six to 20 years. During the follow-up, 8,081 colorectal cancer cases were identified.

Researchers concluded that a diet high in fibre did not reduce the risk of colon cancer, after adjusting for age and other factors such as family history, smoking and red meat intake.

Do we all have carcinogens in our blood?
Each of us likely has pollutants in our blood. A recent study analyzing the blood and urine of a small group of Canadians found varying levels of contamination from heavy metals, pesticides and other toxic chemicals (such as PCBs, mercury, lead). A similar study of 500 Canadians found the same results.

The contaminants included known and suspected carcinogens and other chemicals that may cause reproductive disorders, harm the development of children, disrupt hormone systems or are associated with respiratory illnesses.