Gas and electricity prices have risen sharply this year
The Winter Fuel Allowance should be given to all cancer patients in the UK, a charity has said.
Macmillan Cancer Support says 40% of people who come to it for financial aid need help to pay their fuel bills.
The charity says cancer sufferers feel the cold more because of their treatment and often have little or no income because they are unable to work.
The Winter Fuel Allowance entitles pensioners aged 60 to 79 to £250 each year and those over 80 to £400.
Macmillan questioned 789 people living with cancer to see how fuel prices were affecting them.
Some said that to stay warm they had to wear several layers of clothing at home or just go to bed during the day. Others were using up their savings to pay for heating.
The charity says people suffering from cancer are hit harder than most because they have to spend more time at home due to ill health.
Their immune system is also weakened and they may feel the cold more acutely.
Head of policy Mike Hobday told the BBC: "Lots of cancer patients have been coming to Macmillan telling us that they can't afford to pay their fuel bills this winter.
"They often feel the cold more because of the cancer treatment they've had and at the same time, their income has fallen. They're often not at work or just in more difficult circumstances.
"Some of them, Macmillan can give grants to, but everybody is suffering and what we'd like to do is see the government extend the winter fuel payment to cancer patients in the greatest need."
Energy prices have risen sharply this year, with further rises predicted in the months to come.
In July, supplier EDF Energy put up gas prices by 22% and electricity prices by 17%. A few days later, British Gas owner Centrica followed suit with hikes of 35% and 9% respectively.
An estimated two million people in the UK are living with or recovering from some form of cancer.