Trial treatment provides hope for better ovarian cancer outcomes

An international clinical trial has identified a promising new treatment for the most common type of ovarian cancer.

The international phase II clinical trial of olaparib, a new medication called a PARP inhibitor, was run at 82 sites in 16 countries. Dr Clare Scott, head of the ovarian cancer research laboratory at the Walter and Eliza Hall Institute, a medical oncologist at The Royal Melbourne Hospital (RMH) and an honorary medical oncologist at the Royal Women's Hospital, ran the trial at the RMH site.

The trial results were presented at the 2011 American Society of Clinical Oncology annual meeting in Chicago.

The trial centre at The Royal Melbourne Hospital involved ovarian cancer patients recruited from the Royal Women's Hospital and elsewhere in Victoria. The trial was run concurrently at Melbourne's Mercy Hospital for Women, Sydney's Prince of Wales Hospital as well hospitals in Australia, Europe, Israel and the US.

Around 1100 Australian women are diagnosed with ovarian cancer each year. It is the sixth most common cause of cancer-related death in Australian women, causing more than 800 deaths annually. Unlike some other cancers, there is no reliable way to detect early stage ovarian cancer and recurrence is common, Dr Scott said.

"Most ovarian cancer patients are treated with surgery to remove as much cancer as possible, followed by chemotherapy to kill the remaining cancer cells" she said. "In four out of five patients, this chemotherapy will initially make the cancer shrink, but for many of these patients the response is brief, the cancer regrows and cannot be effectively treated."

The clinical trial tested whether olaparib could serve as a 'maintenance therapy' that would prevent the re-growth of ovarian cancer by extending the remission phase after successful chemotherapy treatment. "We found that patients who received olaparib stayed in remission for more than eight months on average, which was almost four months longer than for those who received an inactive placebo," Dr Scott said.

Olaparib blocks the action of poly ADP-ribose polymerase (PARP), which helps to repair damaged DNA. Some cancers have defects in the ability to repair DNA damage and it is thought that olaparib may make these cancers more vulnerable to cell damage and ultimately cell death. PARP inhibitors are also under investigation in treating some types of breast cancer.

Dr Scott said the study could be an important breakthrough for treating ovarian cancer. "This is the first time a PARP inhibitor treatment used as a maintenance therapy has shown a substantial benefit in delaying disease progression for patients with the most resistant type of ovarian cancer, high-grade serous ovarian cancer."

Dr Scott is separately studying ovarian cancer samples from patients enrolled in the Australian Ovarian Cancer Study to determine which patients and which ovarian cancers may be most suitable for particular treatments. "My laboratory is hoping to narrow down the features which will identify ovarian cancer patients who will respond best to future treatments including PARP inhibitors. If we can do this, we would hope to see even better treatment outcomes for patients. Many ovarian cancer specialists are excited by the outcome of this trial, and are hoping that a large world-wide confirmatory trial will be started in the near future."

(Source: Walter and Eliza Hall Institute: 2011 American Society of Clinical Oncology annual meeting)