Scientists in the UK are investigating a possible link between women's menstrual periods and ovarian cancer.

Often called the "silent killer," the disease has few symptoms in the early stages, meaning that many cases are diagnosed when the cancer is too advanced to be cured. Worldwide, an estimated 125,000 women die of ovarian cancer each year, but its causes are still unknown.

A current theory suggests that the constant injury and repair caused by ovulation may play an important role in causing cancer of the ovaries. During ovulation an egg is released from the ovary, which involves a 'wound' in the layer of tissue overlying the egg. It is thought that in some women this repeated injury and healing eventually causes the cells in the tissue which lines the ovarian surface to change and become cancerous.

Further evidence that supports this hypothesis is the fact that reducing the number of ovulations a woman has during her lifetime -- for example, through the use of oral contraceptives -- decreases their risk of ovarian cancer.

Dr Tanya Shaw and her team at St George's, University of London, are using funding from the Association for International Cancer Research (AICR) to investigate the damage caused to ovarian tissue when an egg is released and how it is then repaired.

Said Dr. Shaw: "By looking at pre-cancerous lesions and ovarian tumours, we hope to improve our understanding of the relationship between the injury, the healing process and ovarian cancer."

Dr Mark Matfield of AICR said: "Often, its only by backing research into new theories about cancer that we will really change our understanding of how different types of cancer are caused -- and how we can treat or prevent them."