But in the last decade, the surgical oncologist at Sunnybrook Health Sciences Centre saw his waiting room undergo a troubling change: A growing number of patients in their 30s and 40s were getting diagnosed with colorectal cancer.

“I knew what to do with the cancer,” said Ashamalla, an expert in minimally invasive surgery at Sunnybrook’s Odette Cancer Centre. “What I didn’t have answers for were questions like: How do I tell my kids? Who’s going to look after them during radiation? What happens to my fertility?

“‘What do I tell my 10-year-old?’ I had to come up with a canned response for that.”

Ashamalla initially wondered if the striking shift in demographics was unique to his waiting room. It soon became clear his clinic was part of a wider trend.

“The studies started coming out showing these steep, dramatic increases of people under 50 with cancer,” he said. “It was exactly what we were seeing.”

Around the world, scientists are tracking a startling surge in cancer cases among young adults. The alarming rise was first seen in colorectal cancer, but cases of early-onset breast cancer, kidney cancer, pancreatic cancer and testicular cancer are also up in people under 50. That healthy young adults are getting diagnosed at disproportionally high rates has put Canadian scientists on alert and racing for answers.

“This started with people born in the late 1980s and early ’90s — the millennials,” said Miranda Fidler-Benaoudia, a research scientist at Cancer Care Alberta’s Department of Cancer Epidemiology and Prevention Research. “But now, we’re seeing increases even among those born more recently.”

Andrew MacDonald was blindsided by his cancer diagnosis.

The former NHL player was 37, active and seemingly healthy, hitting the gym and helping coach his young son’s hockey team.

But in the spring of 2024, MacDonald went to his local hospital’s emergency department with crippling abdominal pain and struggling to urinate and have bowel movements.

Doctors initially believed MacDonald had a missed case of appendicitis and said an abscess on his appendix was pushing against his bladder and causing inflammation. He went home after a few days, a surgery to remove the abscess scheduled for later in the year.

As the weeks passed, MacDonald unexpectedly began to lose weight.

“I started to notice my clothes getting baggy,” he said. “It was painful to urinate, just this odd combination of things.”

In July, MacDonald’s family doctor sent him to specialists, who recommended further diagnostic tests.

“A long story short, they came to the conclusion that it was a tumour, and that it had been growing for quite some time,” he said.

MacDonald, who lives in Oakville, was diagnosed with advanced colon cancer that had spread to adjacent tissue but had not yet metastasized to other organs. Ashamalla, his surgical oncologist, recommended immediate treatment, starting with an ileostomy, quickly followed by 12 weeks of chemotherapy. An ileostomy is a surgical procedure that creates a new way for stool to exit the body; it bypasses the colon and is instead collected in an external pouch.   

With no notable history of cancer in his family, MacDonald said he and his wife, Hali, were shocked by the diagnosis. At the time, their son was nine, their daughter just five.

“They knew that I’d be going to the hospital a lot, and that I wouldn’t be feeling good for a while,” he recalled. “We tried to keep things as normal as possible but it was challenging, for sure.”

Since the 1990s, cancer rates among people under 50 have increased by around 50 to 100 per cent, depending on the study, according to Dr. Lincoln Stein, acting scientific director and head of adaptive oncology at the Ontario Institute for Cancer Research.

For example, a 2023 study in BMJ Oncology found the global incidence of early-onset cancer grew by a staggering 79 per cent between 1990 and 2019. Early-onset cancer deaths also surged by nearly 28 per cent in the same period, with breast, tracheal, lung, stomach and colorectal cancers leading the pack.

“Some of the increase is due to better diagnosis, earlier diagnosis, (and improvements in detecting) small tumours that would have gone unnoticed in a younger individual,” Stein said. “But a good portion of it appears to be real.”

The same trend is happening in Canada, although it appears milder than what scientists are seeing globally. The Star analyzed data from the Canadian Cancer Registry and found the average incidence of all cancers in Canadians under 50 increased by more than 18 per cent from 1992 to 2019, excluding Quebec.

The largest increase was seen in the 20-34 age group, whose incidence rate rose by more than 25 per cent in those 27 years. In contrast, the cancer incidence among Canadians aged 50 and above has remained relatively flat; people age 50-69 even experienced a minor decrease.

That’s despite seniors 65 and older making up the majority — some 66 per cent — of all cancer cases in Canada, according to the Canadian Cancer Society.

“I want to emphasize that cancer still is overwhelmingly a disease of older individuals,” Stein said. “Although it’s rising in younger people, it’s still quite rare.”

In the span of less than five years, Robby Spring and three of her close family members were diagnosed. “None of my immediate family members had cancer before,” said Spring, a 38-year-old Toronto-based patient advocate.

It began with her mom, who was diagnosed at 67 and began her treatments for breast cancer at the end of 2018. Then, at the start of 2023, Spring’s 43-year-old sister was also diagnosed with breast cancer. Two months later, a biopsy revealed a 1.5-centimetre tumour in Spring’s own breast. She was 35.

“I burst out in tears right away, on the table when the radiologist was there,” Spring said. “The first thing that I thought was, ‘I can’t tell my mom. I’m gonna break her heart.’

“One child going through cancer is enough, but then having two daughters at the same time is terrifying,” she said.

The run of misfortune wouldn’t end there. Near the end of 2023, an MRI found evidence that Spring’s 72-year-old father had prostate cancer.

Spring, her mother and her sister’s cancers are now in remission, she said. Her father’s situation is still under surveillance.

“If my sister didn’t have it, mine wouldn’t have been found, and if my mom didn’t have it, my sister’s wouldn’t have been found,” Spring said. She never would have suspected she had breast cancer, given her young age: “In a way, it’s like our mom’s (cancer) saved both of us.”

It’s not just Spring. Breast cancer has been skewing younger and younger, especially in the last decade.

“I was seeing many, many more women in their 20s and 30s than I had seen in the last 20 years,” said Dr. Jean Seely, who heads the breast imaging section of the Ottawa Hospital and is a professor of radiology at the University of Ottawa.

“It started to really register around the time of COVID,” she said. Seely recalled one day when every patient she saw was under 45: “It just felt like an epidemic and I felt nobody was paying this the attention it deserved.”

She analyzed historical data to check whether her experience reflected reality. The results were startling — breast cancer rates rose for all ages over the last four decades, but especially for women in their twenties. In this age group, rates surged by more than 56 per cent since 2001, according to Seely’s 2024 paper.

The increase was made worse by the barriers young people often face in getting diagnosed and accessing cancer care.

“There were so many delays in the diagnosis for breast cancer in these young women that contributed to their poor outcome,” Seely said. “Many of the referring clinicians thought, ‘Well, they’re too young to get breast cancer’ — so they wouldn’t refer them for diagnostic imaging.”

That’s the big question. But scientists are searching for answers.

“It’s actually completely unclear,” said Dr. Keith Stewart, director of Toronto’s Princess Margaret Cancer Centre. “There’s hypotheses, but that’s really all they are. It may be dietary. The younger population (may be getting) less exercise, less fresh fruit and vegetables and more processed foods.”

Emerging evidence suggests our ever-increasing consumption of ultraprocessed foods — salt, fat and sugar-laden ready-to-eat meals and snacks, whose spike in popularity has coincided with a similar surge in early-onset cancer cases — could be a culprit.

Fidler-Benaoudia, the Calgary cancer epidemiologist, said there are few clear links to what causes cancer at young ages, some of which scientists believe will be genetic. But they do want to pinpoint any environmental or other modifiable factors, even though she said it will take decades to unravel.

She said much of the research is in its early stages, and is considered exploratory, rather than definitive. For example, researchers are looking into antibiotic exposure in childhood, which increased in the 1990s, as a potential trigger for early-onset cancer.

Her Alberta research team recently launched a study asking 700 newly diagnosed young adults to think back on their lives and report on a long list of potential cancer exposures. These include everything from diet and physical activity to sexually transmitted infections to tattoos and severe sunburns.

“While the increases in cases are happening quickly, understanding what’s causing them will not be quick,” Fidler-Benaoudia said.

Colorectal cancer has seen some of the largest surges among younger people in recent years; between 2001 and 2021, the incidence rate of those age 35 to 39 increased by 3.7 per cent every year, a 2024 study found. It’s reached the point where colorectal cancer is now the leading cause of cancer mortality in people under 50, according to a JAMA study published in January.

In his clinic, Ashamalla said most young patients have no clear risk factors, and he is careful not to assign blame.

Once he shares the diagnosis, Ashamalla said he focuses on providing his patients with a treatment plan, which he believes counteracts the chaos they often feel after being told they have cancer.

“The gravity — the ripple effect — is profoundly different when you’re dealing with people in their 20s and 30s who have no business being diagnosed with cancer, let alone dying from it,” said Ashamalla.

By December 2024, MacDonald had completed 12 weeks of chemotherapy and five weeks of radiation treatment. The goal had been to shrink the cancer as much as possible in preparation for surgery, and doctors were pleased by the results.

Over the next two months, MacDonald worked to regain his strength. The back-to-back treatments, along with side effects from the ileostomy he had earlier received, had taken a toll.

“When I was playing hockey, I was about 185, 190 pounds,” said MacDonald, who is six-foot-one, and played 10 years in the NHL, first for the New York Islanders, then for the Philadelphia Flyers. “Post-radiation, there was one point when I got on the scale and I was down in the 120s. That was a scary moment.”

MacDonald had cancer surgery in February 2025. During the nine-hour operation, Ashamalla removed large portions of MacDonald’s bowel, along with a portion of his small intestine and most of his bladder. He said that he had Tragically Hip playing through the OR speakers through much of the operation, a nod to MacDonald, who loves the band’s music.

Though recovery was rough — MacDonald said much more painful than any broken bones he suffered in the NHL — the surgery was deemed a success. 

“We got everything out; there was no evidence of cancer in the body after the surgery,” Ashamalla said. “He was rewarded for all the suffering he went through.”

One year later, MacDonald is happy to be on the other side of his gruelling treatment. He said he’s grateful for his medical care and for the constant support of his family, but also that his professional hockey career meant he didn’t have the same financial worries as most young adults diagnosed with cancer. 

“I know there’s people who have a much more difficult road, who have it much worse. I always tried to keep that in mind.”