Women with incurable breast cancer are receiving poor care due to a lack of specialist nurses, according to a new report.
A study for Breast Cancer Care found that just a fifth of NHS organisations have one or more clinical nurse specialists dedicated to women whose cancer has come back and spread.
Advanced cancer occurs when breast cancer cells spread from the breast to other parts of the body, such as the bones, liver, lungs and brain.
It is incurable but some women can live for several years with treatment.
There are an estimated 36,000 people living with this type of secondary breast cancer in the UK and each year around 11,600 die from the disease.
It has been mandatory since 2013 for NHS trusts to collect data on how many women have advanced breast cancer, but only a third do so.
The new study of NHS hospitals and health boards across England, Scotland and Wales, found that 76% agree there is not enough specialist nursing care for people with incurable breast cancer.
Some 95% of women first diagnosed with breast cancer are given access to a named clinical nurse specialist.
But only 21% of NHS organisations had a specialist nurse dedicated to those whose cancer has advanced and is incurable.
A further 33% had a nurse who looked after patients both with incurable cancer and those who were newly-diagnosed.
Some 40% had nurses whose main job involved newly-diagnosed patients but who also did some work with patients who had advanced cancer.
Overall, 47% of trusts said their nurses spent less than a quarter of their time with people who had incurable breast cancer.
Samia al Qadhi, chief executive of Breast Cancer Care, said: "These findings highlight the worrying truth - care for people with incurable secondary breast cancer is not good enough.
"Our survey revealed nurses often lack crucial training to coordinate the complex care and treatment, help people manage often debilitating pain or have conversations about dying.
"And it is outrageous that even though specialist nursing can dramatically improve quality of life for women and men with incurable breast cancer, so many do not have a nurse they can count on for essential support."
"We are calling on NHS clinical commissioning groups and health boards to ensure specialist nursing care is available for all patients with incurable breast cancer and that the right breast cancer services are in place in their hospitals to meet patient needs.
"Only then will everyone living with incurable breast cancer get the care and support they need."
Patient Laura Ashurst, 49, from North Yorkshire, has had incurable advanced cancer for a decade.
She said: "When I had primary breast cancer there were two nurses and I was given a phone number for anything I needed at all. With my secondary breast cancer diagnosis this support is just not there. There's no one person with all the specialist skills to help me through.
"Being told I had incurable secondary breast cancer felt like going into the abyss. It is hugely isolating.
"I've had to find my own way through the dark days."
An NHS England spokeswoman said: "Evidence shows that access to a cancer nurse specialist or other key worker supports a positive patient experience.
"We are working closely with others across the NHS to agree the best way to widen access to specialist support for all people living with cancer, including those living with secondary breast cancer, as part of our plans to transform cancer services across the board."