The union representing medical physicists says extra pay will be needed to encourage more of them to stay in the country.
New Zealand has about 50 medical physicists, who operate the machines that deliver radiotherapy to more than 8000 patients a year.
A recent Health Ministry report says 10 percent of those workers are lost each year, usually because they go overseas.
It says with the rising demand for radiation therapy, swift increases in training numbers and improved retention are needed.
The union, Apex, says that will have to include pay rises, but district health boards will not discuss them until next year.
A patient undergoing radiotherapy. Photo: SCIENCE PHOTO LIBRARY