Olaparib belongs to a group of cancer treatments called PARP-inhibitors, which work by blocking PARP proteins that are involved in a different DNA repair pathway to the one the BRCA genes affect. This causes an accumulation of DNA repair mistakes leading to the death of cancer cells. An international group of researchers treated women affected by relapsed ovarian cancer with olaparib and followed them up for over five years to measure the impact of the drug on their survival.
The authors concluded that: 'Olaparib provided a median overall survival benefit of 12.9 months compared with placebo in patients with platinum-sensitive, relapsed ovarian cancer and a BRCA1 and 2 mutation. Although statistical significance was not reached, these findings are arguably clinically meaningful and support the use of maintenance olaparib in these patients.'
BRCA1 and 2 gene mutations are inherited, and as BRCA proteins are normally involved in DNA repair and act as tumour suppressors, people with these mutations are more likely to get certain cancers, including breast and ovarian. While just 1.2 percent of women in general can expect to develop ovarian cancer, this number rises to 44 percent for women with certain BRCA1 mutations and 17 percent for some BRCA2 mutation carriers.
In this SOLO2 study published in The Lancet Oncology 295 ovarian cancer patients with suspected inherited BRCA mutation who had relapsed following treatment with platinum-based chemotherapy drugs were either put on 300mg of olaparib twice a day or a placebo. The study took place in 123 medical centres in 16 countries and patients were followed up for over five years.
Women who had taken olaparib had a median survival time of 51.7 months from the end of treatment with platinum-based chemotherapy, compared to 38·8 months for women in the placebo group. Though authors were keen to emphasise that though the finding was not statistically significant, the survival time found was longer than previously reported for ovarian cancer treatment with PARP-inhibitor bevacizumab following platinum-based chemotherapy, where patients were shown to have a median overall survival of between 3 years and 3.5 years from the start of chemotherapy.
Over a quarter (26 percent) of patients who received olaparib experienced serious events as a result of the treatment, and four percent of those patients died as a result of the treatment.