Nancy Carter-Bradley, 44, from Hampshire, said the health secretary should ring-fence cancer treatment.
She said her treatment at a London hospital had paused as it was at full capacity and oncologists were helping with the response to coronavirus.
Imperial College Healthcare NHS Trust said it was “exploring use of private healthcare facilities”.
Mrs Carter-Bradley, from Penwood, said she had been dealing with “unbelievable stress” since she was informed her chemotherapy at Charing Cross Hospital for stage three brain cancer would be paused.
Chemotherapy is a cancer treatment in which medicine is used to kill cancer cells. It stops the cells from reproducing, which prevents them from growing and spreading in the body.
Mrs Carter-Bradley said: “With a matter of urgency there needs to be some sort of reassurance with regards to how our treatment can carry on, even if there are delays, rather than a complete stop.”
She said she knew of several other cancer patients who had also had their treatment held.
“To have my treatment stopped without doubt is going to shorten my life span, I don’t know to what degree,” she added.
Source: BBC