New research suggests that the number of older people living with cancer in the UK is set to more than treble over the next three decades.
In 2010, there were 1.3 million cancer sufferers aged 65 and over, but by 2040, it's thought that could increase to 4.1 million.
That means nearly one in four older people would have a cancer diagnosis, according to MacMillan Cancer Support .
The charity says the ageing population, an increased incidence of cancer, and better survival rates are creating a "ticking time bomb" which the NHS must address.
"The care of older cancer patients is the ticking time-bomb for society", says the charity's chief executive Ciaran Devane.
"These stark predictions should act as a warning to the NHS and social care providers of the problems ahead if older cancer patients are not offered the best treatment and support.
"We have a moral duty to give people the best chance of beating cancer, regardless of their age.
"For cancer survival to improve, older people must be given the right treatment at the correct level of intensity, together with the practical support to enable them to take it up.
"The barriers to older people getting treatment must be tackled. If we don't get this right now, many older people will be dying unnecessarily from cancer in the future."
Susan Jenkins, 65, was never denied treatment for her breast cancer, but she feels that because of her age, she was put off having chemotherapy by her oncologist.
"I asked him why he didn't push me to have chemotherapy," explained the retired IT worker from Leamington Spa.
"The response was that I was 60 not 30 and if I was 30 I would have many, many more years in front of me and at 60 potentially I hadn't.
"I was a bit shocked and stunned by it but I didn't say anything."
Having opted for surgery and radiotherapy Susan has had five years clear of the disease.
She now stands up for patients rights, and says while ageism is being addressed there's still plenty to do to raise awareness.
The government says they're working with the charity, and spending £1m to try to improve the situation for the elderly.
A spokesperson from the Department of Health said: "From October 1, 2012, it will be unlawful to discriminate in health and social care on the basis of age.
"Adults of all ages will benefit from better access to services, and for the first time people will have a legal right to redress from the courts if they are unjustifiably discriminated against because of their age."