Fedoruk was recruited by Dr. Harold E. Johns to be the radiation physicist at Saskatoon Cancer Clinic. She became the chief medical physicist at the Saskatoon Cancer Clinic and director of physics services at the Saskatchewan Cancer Clinic. She was a professor of oncology and associate member in physics at the University of Saskatchewan. She was involved in the development of the world's first cobalt-60 unit and one of the first nuclear medicine scanning machines. The cobalt-60 beam therapy unit, or the "cobalt bomb" as it was known, was the first of its kind to successfully use targeted radiation to treat cancer in a patient. The machine's collimated beam of radiation could be adjusted to the size of the tumor to irradiate the growth. Fedoruk's masters work on depth-dose measurements for radiation treatment were essential in the success of the beam therapy unit.