Cancer treatment costs have been described as "a tax on illness" after it was found almost half of patients are cutting back on food and heating so they can afford their prescriptions.
Patients are also going without family outings and holidays due to the mounting cost of prescriptions over a long period of time, a survey for Macmillan Cancer Support found.
The side-effects of treatment, including nausea, fatigue, severe mouth ulcers and diarrhoea, can leave cancer patients needing multiple prescriptions. The cost of which can run into hundreds of pounds every year, the charity said.
Prescriptions are free for everyone in Wales and will be free in Scotland from 2011.
In England, the cost of a prescription is £7.10 per item and Health Secretary Alan Johnson has said there are no plans to abolish the current system.
The Macmillan survey of 477 cancer patients found 44% had cut back on essential items like food or heating to pay for the cost of their prescriptions.
Almost two-thirds (59%) had also cut back on entertainment and leisure activities, including evenings out, family outings and holidays.
A spokesman for the Department of Health said: "People who do pay for their prescriptions can manage the cost by purchasing a three-month or 12-month prescription prepayment certificate (PPC), which allows them to get all the prescription items they need for less than £2 a week."