In 2001, McMillan was forced to interrupt what seemed to be a very promising career to have a malignant tumor removed from his brain. He refused to give up playing, however: he recorded a CD the following year, and in 2003 he was able to give a recital in the Sydney Opera House concert hall. In 2004 he gave a second recital at the Opera House, an all-Australian program.
By 2005 he could no longer play, but he did organize a third concert at the landmark venue featuring five colleagues.
McMillan was featured twice on the Australian Broadcasting Corporation's television magazine Australian Story, and his perseverance and spirit in the face of debilitating illness became an inspiration to many of his compatriots.
More recently, he turned his hospice room into a miniature recording center, assembling a nine-CD set of his various concert and studio recordings which was released last month.