RESEARCHERS have hailed the biggest breakthrough in advanced ovarian cancer for a decade after a new treatment was found to dramatically shrink tumours.

Experts said the results of the early-phase study were "exciting" and "promising" after patients who had exhausted all other treatment options showed an impressive response.

The drug, known as ONX-0801 in the phase one clinical trial, was tested in 15 women with advanced ovarian cancer as part of a wider trial run by the Institute of Cancer Research (ICR) and the Royal Marsden NHS Foundation Trust in London.

The aim was to test its safety, but the results were so good that researchers are keen to move the drug to the next stage of research as soon as possible.

In the trial, which is still ongoing, ONX-0801 significantly shrank tumours in seven of the 15 ovarian cancer patients. In those patients whose tumours had the particular molecular target for the drug, the results were even more impressive, with seven out of 10 women responding.

ONX-0801 is the first in a new class of drugs discovered at the ICR which attacks ovarian cancer by mimicking folic acid to enter and then kill the cancer cells.

Ovarian cancer cells have an abnormally large number of receptors for folic acid, making them particularly vulnerable to the treatment. However, healthy cells are not affected, meaning patients do not suffer the side effects associated with chemotherapy.

Dr Udai Banerji, deputy director of the drug development unit at the ICR and the Royal Marsden, who led the study, said much more research was needed but the results were exciting.

He said: "As this is a completely new mechanism of action it should add upward of six months to patients' lives with minimal side-effects in extremely late phase ovarian cancer.

"This is much more than anything that has been achieved in the last 10 years."

He said if clinical trials proved the drug's effectiveness, it could potentially be used in early-stage disease where "the impact on survival may be better".

The results to date will be presented today [Sat] at the American Society of Clinical Oncology meeting in Chicago.

Although the incidence of ovarian cancer has been steadily falling, in 2015 there were 570 diagnoses of ovarian cancer in Scotland and the disease claimed 362 lives.

Symptoms can include bloating, abdominal pain or swelling, feeling full, or going to the toilet more often, constipation or irregular bleeding. However, diagnosis is often delayed as the signs are mistaken for more common conditions such as irritable bowel syndrome, and around six in 10 cases are identified at a later stage. One in five women are diagnosed at a stage when the cancer has spread and is incurable.

Marianne Heath, 68, a patient who took part in the trial, said: "I had no other treatment choices so felt this was my only option. I had quite a bit of chemotherapy, and now some radiotherapy. There’s nothing left but trials now.

“I do like being on a trial as I feel part of something and just want to feel I am doing something to get better. I feel very well looked after and the Drug Development team at The Royal Marsden are wonderful.

“It gives me and my family a buzz when we are told my scans look better. I just want to keep going so I can keep the tumours at a level where I can enjoy my life.”

Annwen Jones, chief executive of the charity Target Ovarian Cancer, said: "This study shows promising results, although it is a small sample and at a very early stage of research.

"With very few effective treatment options for ovarian cancer, an approach that develops new ways of targeting ovarian cancer cells more effectively, and with fewer side effects, is to be welcomed."