A woman with brain cancer has been told her chemotherapy has stopped because of the coronavirus outbreak.
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.
'Shorten my life'
The mother-of-two, who was diagnosed with brain cancer in 2005, was in remission until October of last year.
When her cancer returned she was put on a course of chemotherapy for a year.
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.
The trust said cancer clinicians were reviewing treatment plans for their patients.
A spokeswoman said: "Drawing on national guidance, they are working through the timing of any surgery or planned treatment in relation to risk. All essential surgery is going ahead.
"We are also taking into account the increase in demand we're expecting across our hospitals over the next few days and weeks."
The NHS has issued guidance to hospitals that cancer treatment should continue unaffected.
A spokeswoman said: "Decisions about treatment are rightly being taken by expert clinicians who will be carrying out as much cancer treatment as possible, while clearly needing to balance this against the risk to individuals posed by coronavirus."
Cancer Research UK said it was not clear how cancer care would be affected and over what timeframe.
Professor Charles Swanton, the charity's chief clinician, said: "As the virus becomes more common in the UK, it will undoubtedly add more pressure to the NHS, bed and ITU availability and hence service delivery.
"We also know that patients suffering from cancer are at higher risk of complications from viral infections such as flu, and Covid-19 is likely to be no different."
The Department of Health and Social Care has been contacted for comment.