"The population we serve here in Northland is a huge rural under-served area, and we are desperately in need of a better space," he said.
"The new facility will see us into the foreseeable future and will give the people of Northland a new, well-designed, attractive and comfortable space for patients with these serious illnesses and their treatments and consultations."
Northland DHB chief executive Dr Nick Chamberlain said having Dr Beatty working as the region's first full-time resident oncologist had been "fantastic".
"This has allowed Northland to start to build our capability and capacity as we look forward to the new cancer treatment centre next year," he said.
"Peter has allowed patients to be cared for by the same oncologist. This continuity is one of the main reasons we want to have our own resident specialists - it's better for our patients."
Dr Beatty described the oncologist's role as to attempt to help cancer patients by treating them in a humane and respectful way to improve their quality of life, and hopefully to extend their lives. His observations over the last two years were that cancer rates for Maori were higher than those of Pakeha, which he put down to a combination of genetics, cultural and social factors. Gastric (stomach) cancer, in particular, was a big issue for Maori.
There also seemed to be a slightly higher rate in breast cancer and asbestos- and sun-related cancers.
And despite being in the field for more than 30 years, he still had cases that pulled on his heart strings.
"I have a number of people right now who are sweet, kind, and have done nothing to deserve this. I have a 20-year-old woman who has got a rare cancer, and her family pay $8000 a month for treatment. It's incurable, and that's hard," he said.
He was no stranger himself to the suffering cancer patients endured on a personal level, having lost his wife to breast cancer in 2002, and subsequently raising three children.
"It was a struggle for me to be her husband and being a doctor. It was a humbling experience to go through," he added.
Perhaps as a result, he took a pragmatic view of life and death: "I don't know if I'm going to make it home tonight, I can't predict how long people are going to live, but I can focus on making sure people have a good quality of life and making their journey as comfortable as it can be.
"Every week I see a lot of tragedy, but I also have a lot of miracles, and that's a good feeling."
Dr Beatty will return home next year because his son, who has been house sitting for him, is graduating from medical school in May and moving on.
"I will be disappointed to miss the opening of the oncology unit, however these things usually take longer than planned (to come to fruition), and I am pleased I will have had something to do with it," he said.
He did not wish to disclose the amount he had donated.
Meanwhile the Northland Community Foundation is embarking on a final push to raise $1 million by October 31 to reach its Project Promise goal of $3 million for the construction of the cancer treatment unit.
More about Project Promise at www.northlandcommunityfoundation.org.nz.