[5] After graduating, Hagen pursued a mixed internship in Christchurch, New Zealand, in 1980, gaining valuable international experience in his early medical career.

[6] John Hagen has worked for over 37 years as a staff surgeon at Humber River Regional Hospital (HRH), specializing in laparoscopic surgery and advancing minimally invasive surgical techniques.

[3] In 2014, he was honored with the Mentor of the Year Award - Region 3 (Ontario and Nunavut) by the Royal College of Physicians and Surgeons of Canada.

[10] Hagen has organized and led seven trips to China, where he and a team of North American doctors provided interactive lecture sessions at hospitals across the country.

As part of the exchange program, two minimally invasive fellows from Toronto are sent to China, while two Chinese surgeons visit Humber River Hospital for a period of 6-8 weeks.