Up to 850 women in England and Wales could benefit from a targeted pill that treats ovarian cancer after it was approved for use on the NHS through the Cancer Drugs Fund.
The National Institute for Health and Care Excellence (Nice) said niraparib will be made available to adults with relapsed, high-grade serous epithelial ovarian, fallopian tube or primary peritoneal cancer who have had two or more courses of platinum-based chemotherapy.
Ovarian cancer is one of the most common types of cancer in women. In 2015, 6,198 people were diagnosed with the disease in England.
UK rates are among the highest in Europe but the country has one of the lowest survival rates.
The charity Target Ovarian Cancer described the move as a "game changer".
Clinical trial results showed that niraparib delayed cancer growth by around six to 15.5 months more than a placebo, depending on a woman's genetic profile.
However the final results on overall survival were not available so it was not clear whether niraparib increases the length of time people live.
Niraparib, a once-a-day pill, works by inhibiting two proteins involved in DNA repair to prevent cancer growth.
Rebecca Rennison, director of public affairs and services at Target Ovarian Cancer, said: "Today's announcement is a game changer in ovarian cancer.
"While we have seen some new treatments in recent years, these have been for highly restricted groups.
"With niraparib, we're taking the fight to ovarian cancer. We know that with the right investment in new treatments, more women can and will survive this disease. Today is a critical first step in making that a reality."
Ovarian cancer patient Jane Howarth, 54, from Manchester, has been taking niraparib for nine months.
She said: "When I was first diagnosed with ovarian cancer in 2015, my first words were, 'But I've got children!'
"They were 11 and 14 at the time. I am now told that the cancer is advanced and incurable, but last September I started taking niraparib - and now I am at home, stable and well.
"I am there for my older daughter as she goes through her A-levels. I am there for my younger daughter as she navigates adolescence. We can make plans, and that is invaluable. I believe all women living with this disease should have that, too."
Meindert Boysen, director of the centre for health technology evaluation at Nice, said: "The outcome for women with ovarian cancer is generally poor, with less than 35% surviving for five years after diagnosis.
"We are pleased to see the inclusion of niraparib in the Cancer Drugs Fund as it will give women early access to this treatment while uncertainties in the clinical evidence can be addressed through the collection of additional data."