Dr Brennan, who has spent his entire career in the United States, will today give a graduation address in Dunedin. He has another link to the South, because son Sean is a Gibbston winemaker, a fact Dr Brennan finds remarkable, given his son grew up in the US.
Dr Brennan bluntly admits that a ''big ego'' came with being a high-profile surgeon.
He performed his last operation only a few months ago, joking yesterday he was determined to stop two years before someone told him to. He now has to reinvent himself - there is no plan to retire, or at least, he ''will not let retirement interfere with work''.
He is vice-president and international programmes director at the Bobst International Centre in New York.
He is also forthright about the US health system: ''It's broken, completely broken''. It was a situation in which everyone - patients, doctors, hospitals, insurers - were ''villains''.
Patients had unrealistic expectations, yet the main failure was of the US as a wealthy country not providing a universal healthcare system.
The very poor were looked after by the existing system, he said, and it remained to be seen how successfully President Barack Obama's reforms plugged more of the gaps.
He is grateful for the free education he received as a student in the 1960s, but said New Zealand students should still be pleased higher education is cheaper here than in the US. Originally from Auckland, the former student union president and Otago rugby representative said his Dunedin education set him up for his high-flying career.
He did not want to sound boastful, insisting he was ''not the smartest guy in the class''. Hard work propelled him to the top of his profession, a feat most people could achieve if they put the hours in. In the early days of his surgical career, he worked 100 hours a week, and then 80 hours a week for about 30 years.
''I did it because I played the game. I wanted to do it.''
He said his son's achievements - winning a top international wine award in London this year - had outstripped his own. Dr Brennan founded an Otago alumni association in the US about 10 years ago, and it has since raised about $2 million for the university.
He was chairman of the department of surgery at Memorial Sloan-Kettering Cancer Centre, from 1985 until mid-2006.
He has also served as director of the American Board of Surgery, chairman of the American College of Surgeons Commission on Cancer, president of the Society of Surgical Oncology, vice-president of the American College of Surgeons, and president of the American Surgical Association. He has received the American College of Surgeons' highest award, the Distinguished Service Award.
