Radiation therapists will rally at several health sites across Victoria to protest moves to replace senior radiation therapists with lower paid managers.

The statewide protests begin Wednesday afternoon, with their union saying Alfred Health's decision to replace senior radiation therapists with generic managers is a cost-cutting measure that will compromise patient care.

Alfred Health said the issue is being considered by the Fair Work Commission on Wednesday. "There are several inaccuracies in the statement released today by the Victorian Allied Health Professional Association," a spokesman said.

VAHPA secretary, Craig McGregor, said the hospital was pushing the major changes to its radiation oncology department, contrary to recommendations of their own expert report and the view of the state government's health workforce experts.

Mr McGregor said the move means graded therapists would be replaced by generic operations managers not required to have clinical experience in radiation therapy or any knowledge of the physics of ionising radiation, used in high doses by radiation therapists, to treat cancer.

"The idea that a generic manager, without a degree in medical radiations and lacking the necessary clinical expertise, could properly run a radiation oncology department is foolishness born of ignorance," he said.

"We are hugely concerned by the potential health implications of this move."

The rally coincides with the commission's hearing on Wednesday, in which the union is seeking to have the decision reversed.

Protests are expected at the Alfred's campuses, Austin Hospital, Barwon Health and Peter MacCallum Cancer Centre.

Alfred Health said it cannot comment further while the issue was being considered by the Fair Work Commission.