A study by doctors from Singapore General Hospital (SGH) has revealed that an aggressive form of ovarian cancer may be more common in Singaporean women than those from Western countries.

Known as the clear cell cancer, the number of patients diagnosed with the disease in Singapore has more than doubled in the last two decades, rising from 5.2 per cent to 13.4 per cent of the overall ovarian cancers reported. The incidence in Singapore is also higher as compared to other countries such as United States, Italy, Norway and Australia.

The SGH team has also discovered that endometriosis is a common risk factor among women with clear cell ovarian cancer. Out of the 81 patients with clear cell ovarian cancer and 175 patients with other ovarian cancers diagnosed from 2004 to 2009, almost half of the patients with the aggressive form of cancer had endometriosis – a widespread disorder among women in Singapore.

Findings from the study also show that ovarian cancer patients who were never pregnant or delivered are more likely to have the clear cell subtype, compared to other ovarian cancer patients who had at least one pregnancy or delivery.

To determine if an ovarian mass is cancerous or benign, doctors often use the Risk of Malignancy Index, which is a standard scoring system, to help them in their assessment. However, the study has found the index to be an unreliable predictor for clear cell subtype of ovarian cancer.

“Local data on clear cell ovarian cancer is lacking. It is important for us to study and understand the disease to find better diagnosis and treatment methods especially when clear cell ovarian cancer is more common among Singaporean women,” said Associate Professor Tay Sun Kuie, Senior Consultant, Department of Obstetrics & Gynaecology, SGH and lead investigator for the study.

Survival rates for patients with the aggressive clear cell ovarian cancer are generally worse than those who have other ovarian cancer subtypes. Its outcome of treatment is also poorer. Despite treatment with standard chemotherapy, 52 to 86 per cent of patients will experience worsening of the disease over time.

The findings from the study were presented at the 8th Singapore International Congress of Obstetrics and Gynecology in August this year.