There will be a record 2.5 million people living with a cancer diagnosis in the UK in 2015, an analysis by Macmillan Cancer Support predicts.
The charity says the surge will create a crisis of "unmanageable proportions", despite improvements in survival and diagnosis being partly behind the rise.
It says political parties need to take urgent action.
Department of Health officials say survival rates are now at their highest ever in England.
The report says the growing older population has contributed to the rise - an increase of almost half a million people "living with cancer" in the last five years.
The figure includes people who are undergoing treatment and those who have been given the all-clear.
Lynda Thomas of Macmillan Cancer Support says: "While it is great news that more people are surviving cancer or living longer with it, progress is a double-edged sword.
"As numbers surge, the NHS will soon be unable to cope with the huge increase in demand for health services.
"As we are threatened by a cancer crisis of unmanageable proportions, all political parties must step up and make a real commitment to supporting people with cancer."
The charity estimates around a quarter of people treated for cancer in the UK continue to need NHS care after being clear of the disease.
John Pearson, 47, who was diagnosed with bowel cancer in 2006, said: "Eight years on from my diagnosis I'm still suffering fatigue and permanent nerve damage to my legs, hips and arms from the chemotherapy.
"I try to stay positive as I've survived cancer but I'm living with the long-term side-effects of treatment.
"I wish I could do without the health services but I can't - I see my GP for help with pain control, and have to visit the hospital for colonoscopies, neurology, and physiotherapy."
Cancer Research UK's head of statistical information, Nick Ormiston-Smith, said: "Cancer is mainly a disease of old age so as we live longer, more people will develop the disease.
"This means the number of cases will increase as the UK population ages. Research has also led to improvements in survival so more people are living longer following a cancer diagnosis.
"It's essential that the next government increases investment in the NHS, particularly in diagnostics and treatments, so our cancer services are fit to deal with the increasing demand of an ageing population and can ensure the best possible results for patients."
A Department of Health spokesperson said: "It is hugely welcome news that over the last five years 500,000 more people are able to live with cancer - part of the fact that cancer survival rates are increasing from a relatively poor performance by European standards to their highest ever level in England.
"The NHS is rising to the challenge this presents and is seeing 51% more patients with suspected cancer than 2010, offering cutting-edge drugs through the cancer drugs fund, focusing on high quality compassionate care as never before, and working to introduce a personalised recovery care package for every patient."
Macmillan Cancer Support's analysis includes projections of future cases based on research published in the British Journal of Cancer in 2012.