Cancer is becoming an increasing problem as the population ages
Up to 15,000 people aged over 75 may be dying unnecessarily from cancer each year in the UK, according to research.
The North West Cancer Intelligence Service said their lives would be prolonged if UK cancer survival rates matched the best in Europe and the US.
Researchers said delays in diagnosing cancer in the UK and poorer treatment after diagnosis may be to blame.
The government's national cancer director said urgent action was needed over the study's findings.
More invasive cancers
Later diagnosis, either through delays by the patient or the NHS
Patient decision to avoid intensive therapies
Cancer survival rates are calculated on the basis of those who are alive five years after diagnosis.
The researchers, who will present their findings to the National Cancer Intelligence Network, said the number of under-75s dying in the UK was down, but little progress had been made among over-75s and the gap with other countries is growing.
Research into breast cancer survival rates, for example, shows that women aged over 75 have a lower chance of survival than for all ages, a difference which does not appear to be explained by their age alone.
18 MONTHS BEFORE DIAGNOSIS
Maryam Valantin's mother, Mahin Joulaie, was told she had advanced ovarian cancer at the age of 74
"Mum started to have bleeding early in 2007.
She went to the GP, but they just took her off her HRT and sent her to a gynaecologist. He said it was probably just stress.
It was only when she went back to visit family in Iran and saw a doctor there that she was diagnosed.
They did a scan and found a large lump in her fallopian tube.
When she came back to the UK, doctors found the cancer had spread to one of her lymph glands. It was the size of a tennis ball.
She then had a six-week wait before having a hysterectomy and then chemo.
Her treatment was very good, but the diagnosis was abysmal.
If it had been found 18 months earlier, it could have been removed easily and she wouldn't have needed a hysterectomy or chemo."
Dr Tony Moran, lead researcher from the North West Cancer Intelligence Service, said elderly cancer patients did not appear to be benefitting from the improvements in treatments in the last decade.
He calculated that if the UK was performing as well as Western Europe in the age group 75-84, and as well as the US in the 85 and over age group, there would be 15,000 fewer cancer deaths among the elderly every year.
At present, 75,000 over-75s die every year of cancer.
Most worryingly, UK cancer deaths in the over-85s went up by 2% over an eight-year period, while in Western Europe they went down by 16%.
Possible reasons include the UK being more susceptible to certain cancers related to the way we live, but many experts think it unlikely given the similarities in Western lifestyle and diet.
The other possibilities include later diagnosis, and poorer treatment once that diagnosis has been reached.
"The circumstantial evidence does suggest later diagnosis," said Dr Moran. "But there are many stages where these delays may occur - the patient, the GP or the hospital."
There are surveys which indicate a lack of awareness that the chances of developing cancer increase with age, and also the notion that a "stiff upper lip" mentality may prevent some of the older generation seeking advice.
It has also been suggested that some doctors and patients may together conclude that intensive therapy is not the best option given the toxic side-effects.
"The point is we don't know why this is happening," said Dr Moran. "Elderly cancer survival is an area which has been grossly neglected. It is crying out for research."
Professor Mike Richards, national cancer director, said: "This is an important study and urgent action needs to be taken on the findings.
"We need to ensure that cancer patients of all ages are diagnosed as early as possible and receive appropriate treatment.
"The findings have already been shared with the National Cancer Equality Initiative and we will be working with the NHS and other interested parties to tackle any age inequalities."
Michelle Mitchell, charity director for Age Concern and Help the Aged said: "People over 65 are hugely under-represented in trials of cancer drugs, despite the fact that the majority of cancers occur in older people.
"This means that clinicians don't have good information on which drugs are most effective and well-tolerated in older people with cancer.
"If the UK wants to improve its cancer mortality rates among over 75s, it should start by giving older people fairer access to clinical trials and extending the upper age limits for bowel and breast screening services."
Mike Hobday, Head of Policy at Macmillan Cancer Support: "It is appalling that people over 75 are not getting the care they need from the NHS.
"With an ageing population, the numbers of people getting cancer are increasing year on year.
"This country offers some of the finest treatment and support in the world and it is scandalous that not everyone is getting this."
But Professor Alan Maryon-Davis, president of the UK Faculty of Public Health, said: "As usual the people mostly missing out are from our most deprived communities. That's where the real cancer gap is."