'We should pay attention': N.S. oncologist explains link between alcohol and cancer

Canada's new guidance on alcohol that warns about the risks between drinking and cancer is being welcomed by a leading Nova Scotia oncologist.

The report, released in January, delivered the message that more than two drinks a week increases the risk of several types of cancer.

That the risk rises with every additional drink of alcohol.

"It is a carcinogen and something that we should pay attention to," said Dr. Bruce Colwell, a medical oncologist who is also in charge of systemic therapies with Nova Scotia's cancer care program and an associate professor at Dalhousie University in Halifax.

While the links between alcohol and cancer have been known for decades, the most recent report by the Canadian Centre on Substance Use and Addiction makes it clear there is no safe amount to drink.

"We should look at something that causes cancer and try to avoid it as much as we can," Colwell said.

The report identifies breast and colon cancers as the most common that are connected to drinking, followed by cancers of the rectum, mouth, throat, liver, esophagus and larynx.

There are a number of theories around how that happens.

"There is a breakdown product of alcohol called acetaldehyde and that is a known carcinogen. It will cause damage to DNA and will directly cause cells to become cancerous," Colwell said.

Furthermore, there is evidence alcohol itself causes cancer through a process called oxidation, Colwell said. And alcohol can also increase estrogen levels, he said, which is a risk factor for breast cancer.

Pinpointing the causes of cancer in his own patients is difficult, he acknowledged, where a number of other factors such as a person's diet can also be at play.

He is also not there to judge anyone when he's treating them. 

"It is really hard with alcohol being so prevalent to say that is why you got the cancer but we know through these big studies that people who drink less will have lower incidence of cancer," he said.

Age remains the biggest risk factor for cancer as DNA becomes damaged naturally when people get older, he notes.

Nearly half of Canadians unaware of risks

Cutting down on drinking is one of the key ways people can reduce the risk of cancer, according to the Canadian Cancer Society.

The charity now wants to see action following the report's release, including implementing warning labels on alcohol products.

"Over 40 per cent of Canadians are not aware that alcohol consumption increases these risks and so this is a good opportunity for people to have information to have conversations and to make reflections," said Ciana Van Dusen, advocacy manager of prevention for the Canadian Cancer Society.

Statistics from 2015 linked more than 3,000 new cancer cases across the country to alcohol, Van Dusen said, with a forecast the number could jump to more than 10,000 by 2042.

Similar to previous studies connecting smoking to cancer, Colwell expects it will take some time before there is a big impact from the new guidance.

However, he sees it as a good thing there is now clear information for people to consider.

"There is no one that starts smoking today that doesn't know the harm they're doing," he said. "When they start getting up to drinking more than two drinks a week then you have to start thinking. That is a balance and hopefully they will think about it beforehand."

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