Dr. Sean Cleary was a gifted surgical oncologist and generous educator, but what made him uniquely brilliant was his extraordinary ability to make people feel valued, cared for and inspired.Michelle Siu/The Canadian Press
A few years ago in Cincinnati, two cancer surgeons were watching a video of a minimally invasive liver surgery. The doctor who performed the operation, Adnan Alseidi, always welcomed feedback from his friend and surgical colleague Sean Cleary, a world-renowned expert in their field.
Dr. Cleary’s insightful comments left Dr. Alseidi feeling buoyant. It was only later that it dawned on Dr. Alseidi what had actually happened; he had just been schooled.
“I remember feeling really good after his comments. But then I realized that he was actually telling me about something that I could’ve done much better,” Dr. Alseidi, an associate dean with the University of California San Francisco, recalled with a chuckle.
“One thing that was really amazing about him was how he could make you feel good, even if he was actually telling you that you did something wrong.
“I’ve never done that [error] again in my life.”
For Dr. Alseidi, this encounter was classic Dr. Cleary. He was a gifted surgical oncologist and generous educator, but what made him uniquely brilliant was his extraordinary ability to make people feel valued, cared for and inspired – even while he was critiquing them or pushing them to be better.
This constellation of talents made Dr. Cleary a beloved and effective leader, as well as a global star in hepatopancreatobiliary (HPB) surgery, a highly specialized field that treats cancers and other conditions involving the pancreas, liver and bile ducts. He has held leadership roles at major surgical societies – including being president of both the Canadian Association of General Surgeons and Americas Hepato-Pancreato-Biliary Association – and was a prolific researcher, with more than 190 papers bearing his name.
Dr. Cleary spent much of his childhood abroad and worked for seven years in the United States, but Canada was always his home. In 2023, he returned from the U.S. to accept an appointment with the University of Toronto as the Langer Chair of the Division of General Surgery, supporting some 165 surgeons across nine hospitals. At the University Health Network, he was building one of Canada’s largest and most advanced robotic surgery programs.
Despite his unfathomably busy schedule, Dr. Cleary made time for everyone in his expansive orbit but was a family man above all, fiercely devoted to his wife and two sons. At Toronto General Hospital, where he worked as a surgical oncologist, he was known to his peers as a “surgeon’s surgeon,” technically brilliant and unflappable. But he was widely adored; by everyone from the nurses, who became intimately acquainted with his boisterous laugh and love for the Tragically Hip, to the operating room attendants, who appreciated Dr. Cleary as the rare surgeon who always remembered their names.
Dr. Sean Cleary, second from right, while performing a surgical procedure to remove part of a patient’s liver, using a stereoscopic laparoscopy system.UNIVERSITY HEALTH NETWORK
And for thousands of patients, Dr. Cleary was the source of profound comfort, even as they battled some of the deadliest cancers and conditions. “Dr. Cleary, an extremely busy man, gave me more time than any doctor I have ever met,” George Emerson, a former patient who has a rare genetic disorder, wrote in an online essay. “He gave us scientific insights, practical advice and hope. He even made us laugh.”
Mr. Emerson felt reassured that if anyone could save his life, it would be Dr. Cleary. But he never got a chance to try; on Aug. 10, just days after their first meeting, Dr. Cleary died after being pulled from the waters of Kempenfelt Bay in Barrie, Ont., where he was competing in a triathlon.
He was 52. Dr. Cleary leaves behind his wife, Janice Clugston; beloved sons, Owen and Christian; parents, Eleanor and Michael Cleary; and sisters, Lisa Reid and Stephanie Cleary.
Sean Patrick Cleary’s life began on Nov. 1, 1972 in Toronto. His father worked for Proctor and Gamble, a career that uprooted the Cleary family every few years to far-flung European locales like England, Vienna and Brussels.
Despite his itinerant childhood, Sean was a consistent straight-A student. His parents recalled how at the age of 10 or 11, they caught their son staying up late, reading textbooks under his covers with a flashlight.
Even as a boy, he had an “endless desire to learn” and applied his technical mind to every pursuit, said his sister Ms. Reid. As a result, he excelled at everything he tried, including sports (especially tennis, skiing and hockey, his greatest love), music (singing, flute and piano) and theatre (Ms. Reid once watched her brother play Dr. Frank-N-Furter in a high school performance of The Rocky Horror Show).
For Ms. Reid and her sister, their big brother was a best friend, protector and trusted confidant.
“You could be sitting in the midst of a loud restaurant with lots going on, and feel like you’re the only person with his attention,” Ms. Reid said. “He really had the ability to listen, without judgment.”
Medical school was a natural progression for the teenager who excelled at math and science, and after attending Queen’s University, he studied medicine at Western University, where he also met his wife.
He did his surgical residency and HPB fellowship at the University of Toronto, quickly proving himself to be a rising star.
“He always was on a higher level,” recalls Carol Swallow, the RS McLaughlin Professor and chair of the Department of Surgery at U of T, who knew Dr. Cleary since he was a resident. “He had a great ability to perceive where the problems were, what the solutions could be and then negotiate and get things done.”
In 2016, Dr. Cleary was recruited to the prestigious Mayo Clinic in Rochester, Minn., where he gained experience with robotic surgery.Andrew Jeffrey/UNIVERSITY HEALTH NETWORK
As a new hire at Princess Margaret Hospital, Dr. Cleary developed his own research program in cancer epidemiology. He also became keenly interested in minimally invasive surgery, which was still novel at the time. In a 2022 podcast interview, he remembered asking his superiors about pursuing this new approach for liver surgery. “Their response was kind of like, okay, that’s nice, Sean. Good luck with that,” he recalled.
So together with a few close friends, Dr. Cleary effectively taught himself to perform minimally invasive surgery by watching videos, seeking out weekend courses internationally, and practising on pigs before finally attempting it on human patients. “We were some of the first in Canada to do this stuff, and we did it together,” said Alice Wei, a longtime friend and fellow HPB surgical oncologist. “I think we really built a powerhouse in Toronto.”
In 2016, Dr. Cleary was recruited to the prestigious Mayo Clinic in Rochester, Minn., where he gained experience with robotic surgery, an area where Canada is woefully lagging. Together with Dr. Alseidi, he built a registry for minimally invasive liver resections in the Americas – a powerful resource that’s grown to become the largest of its kind worldwide, according to Dr. Alseidi.
His time in the U.S. also gave him a deeper appreciation for the Canadian health care system, he told Toronto Life magazine in April, 2025. After six years at Mayo, Dr. Cleary and his family decided to move home in 2023, amid a political climate that was increasingly anti-science and poised to re-elect Donald Trump as U.S. president.
“I took my car to get serviced in Rochester, and Fox News was playing on TV,” he told Toronto Life, recalling the moment that crystallized his decision to repatriate. “I tried to ignore it, but I just couldn’t sit there. I ended up grabbing a cab rather than waiting any longer.”
At a UHN memorial for Dr. Cleary in late August, a room packed with devastated friends and colleagues grappled with the loss of someone who had been an “anchor.”
Timothy Jackson, UHN’s division head of general surgery, implored his colleagues to honour Dr. Cleary’s legacy by “living out the same spirit of excellence, humility and compassion that he showed us every day.”
“In moments when we doubted ourselves, he poured belief into us,” he said. “That is why no matter who you are – whether you trained Sean or Sean trained you – he will always be remembered as a true mentor and role model for all of us.”
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