Healthcare workers caring for cancer sufferers must encourage them to be more physically active, a charity said after it emerged that the majority of medics do not tell their patients to exercise.
Four in five cancer patients said their GPs, oncologists and clinical nurse specialists did not speak to them about the importance of being physically active, according to Macmillan Cancer Support research.
The poll of 1,098 cancer patients also found that 37% are not physically active at all.
The charity said being active during and after treatment can minimise the side effects and could help prevent recurrence and dying from the disease.
Ciaran Devane, chief executive of Macmillan Cancer Support, said: "This new research shows that the message is still not being passed on to cancer patients about just how important it is for them to keep active.
"We know that people going through gruelling cancer treatment tend to feel out of control and it can be a very frightening time. Knowing what you can do to help yourself and your recovery is both encouraging and helpful.
"It is crucial that health professionals encourage people living with cancer to stay physically active and Macmillan will continue to work with and support them to ensure that this happens."
Clinical oncologist Jane Maher, chief medical officer at the charity, added: "As a cancer specialist it's hard to encourage people to think about fitness during and after gruelling cancer treatment. It's easier to tell people to rest.
"But increasingly, many patients will need our help to bust the myth that resting up is always the right thing to do, so they do not miss out on the wonder drug of exercise, which can make all the difference to recovery."