The cancer specialists today have criticized the "disappointing" decision of the health watchdog to not recommend a drug for ovarian cancer.
The National Institute for Health and Care Excellence (Nice) stated that olaparib is not considered economically effective.
The "pioneering" drug is available on the NHS for women with ovarian cancer who have inherited mutations in BRCA genes.
Studies have shown that more women could also benefit from the drug. But Nice says it will not expand its use in draft guidelines.
In 2016, 6,430 people were diagnosed with ovarian cancer in England and over 4,000 women die each year in the United Kingdom.
Health leaders have decided not to recommend a drug called olaparib (pictured) that could help thousands of women fight advanced ovarian cancer
The United Kingdom has the worst five-year survival rate for ovarian cancer in Europe, with six out of 10 cases in England diagnosed at an advanced stage.
Between 5-15 percent of ovarian tumors are caused by defective genes, called BRCA, that can be identified through genetic testing.
Nice said the results of the clinical trials showed that olaparib, which is also called Lynparza, lengthens the time until the tumor gets worse compared to placebo (about 8.4 months with olaparib and 4.8 months with placebo).
He said that this benefit is greater in the BRCA mutation positive subgroup, for which Nice has already recommended olaparib as a third-line treatment.
How Olaparib works
Olaprabic, or Lynparza, was developed by researchers from the Francis Crick Institute in London and the University of Oxford.
Scientists have discovered a weakness in cancer defense.
Cancer grows when a defect in normal DNA prevents it from repairing itself.
But cancer cells also need DNA repair mechanisms to survive, so they use a "spare" repair process – a protein called Pol-theta – which usually healthy cells do not need.
This dependence on Pol-theta leaves cancer vulnerable to attack because if scientists can block its only way of survival, cancer can not recover after being detonated with radiation.
Olaprabico, takes as a capsule, blocks the ability of cancer cells to repair themselves.
They hope this means a lower dose of radiation that can be used, saving healthy tissue while having a greater effect on cancer.
It is the first of a group of drugs called PARP inhibitors.
Like any medication, it has side effects, including headaches, nausea, skin reactions and dizziness.
The drug has now been approved for women with ovarian carcinoma and hereditary mutations to BRCA breast cancer genes and clinical trials continue in other patient groups.
Olaparib, carried out by British universities, was found to extend the lives of seriously ill women with this type of ovarian cancer in a 2013 study.
Two thirds of patients treated with the drug had no relapses within three years, compared to a third among those given a placebo.
The results have been described as "exciting" by the doctors.
But because of the cost of £ 4,635 for the innovative 28-day cycle tablets, Nice does not recommend it as a maintenance treatment for adults with ovarian cancer, fallopian tube and relapsed peritoneal tumor, sensitive to platinum.
Professor Paul Workman, executive director of the Institute of Cancer Research (ICR) in London, said the decision was "disappointing for women with advanced ovarian cancer and for their doctors".
"The use of olaparib in women without BRCA mutations would be more clearly cost-effective if we could learn more about which women benefit from and have had a better test to select them for treatment," Prof Workman added.
"We would like to see the olaparib available on the NHS for a larger group of women, to provide them with an important new treatment option."
Alex Holden, of the Target Ovarian Cancer Association, said: "Any reduction in treatments is a disappointment and a blow to women with ovarian cancer in the UK.
"This is a disease that needs more treatments, not less, and more investment in ovarian cancer research is desperately needed to find tomorrow's treatments."
Approximately 27% of all cancer patients receive radiotherapy, with more than 130,000 people in England receiving treatment each year.
Treatment is very effective but can have long-term side effects because healthy tissues are also irradiated.
Olaparib reduces this impact by "sensitizing" cancer cells to radiotherapy and reduces the amount of radiation required.
The draft guidance is open to public consultation until 30 November and the final orientation should be published in April 2019.