The three stars shared those heartbreaking stories on Wednesday as they helped announce a Canadian component to the popular Stand Up To Cancer (SU2C) broadcast fundraiser in the U.S.
"The statistics are staggering: two out of five Canadians are expected to develop cancer in their lifetimes," Aykroyd told a news conference. "Every hour of every day, 22 Canadians will be diagnosed with some type of cancer — nine of these people will die from the disease. It is the leading cause of death in Canada."
"In my own life, cancer has taken my neighbour ... (as well as) my great friend Barbara Orbison, Gilda Radner, of course, my writing partner Tom Davis — and two days ago my business manager of 30 years, Barbara Bryson," added the Oscar-nominated "Saturday Night Live" alum, who was born in Ottawa.
All four of Canada's English-language network broadcasters — CBC, City, CTV and Global — plan to join dozens of U.S. channels in simultaneously airing the live, one-hour SU2C telethon commercial-free on Sept. 5 at 8 p.m. ET/PT.
Several SU2C specials have already aired across the U.S. from Hollywood (in 2008, 2010 and 2012), with celebrities including Michael Douglas, Tom Hanks and Gwyneth Paltrow, who is a co-executive producer for this year's U.S. telecast.
But this is the first time Canada is participating in the event, which raises money to support education and awareness programs as well as "Dream Teams" of collaborating cancer scientists and clinicians.
"We need to wait for the telecast, but what I expect at the end of this will be very ambitious research programs — as the types that we've seen in the U.S. — are going to be possible here in Canada," said Dr. Tom Hudson, president and scientific director of the Ontario Institute for Cancer Research.
Organizers say more than $260 million has been pledged to the SU2C initiative since it was founded in the U.S. in 2008.
This year's special will see celebrities rallying for the cause both from Hollywood and Toronto. Viewers in Canada will have the opportunity to donate via the web and a Canadian-specific toll-free number.
Ferguson, who plays Mitch on "Modern Family," is a Stand Up To Cancer Canada (SU2C Canada) celebrity ambassador along with Aykroyd and MacLachlan. He said the cause hits close to home because of husband Justin Mikita, a lawyer who was diagnosed with Hodgkin lymphoma at age 13.
"He has been cancer-free for 15 years now, but I think when you are a survivor of cancer, that's something that you carry with you for your entire life," said Ferguson. "It's a badge of honour, in a lot of ways, and there's always that fear of it coming back.
"So every year he goes in for his checkups and he's really aware of his body in a way that I'm not necessarily with mine, having never had cancer. He's always telling me to get things checked up on my body, like if I have a weird mole or something.
"So it's with him for the rest of his life and then, in turn, it's with me as well."
MacLachlan, star of "Twin Peaks" and "Sex and the City," said his mother died of ovarian cancer in 1986 after battling it for five years. She was 51.
"She had a large growth in her ovaries. They said it was the size of a pineapple, and ovarian cancer is insidious because it's very, very difficult to detect."
His father later died after surgery for colon cancer took a toll on his health.
"Both of them had very difficult battles," he said. "It was hard to watch and if anything can come out of that, it's this sort of galvanization of wanting to do something to affect these diseases and be a spokesperson and use whatever celebrity I have to sort of focus attention on this organization in particular."
SU2C Canada is a program of the charity EIF Canada.