The ovaries of every woman contain their maximum number of eggs or oocytes at a time approximately half way through fetal development. From birth, there is a steady decline in the number and quality of remaining eggs and this continues until the pool is almost entirely depleted and menopause occurs. As a result of this decline in remaining egg number or ovarian reserve, female fertility declines more rapidly after the age of 35 and the years preceding menopause at average age of 51 years are characterised by relative infertility.
Women that undergo treatments for cancer that include surgery, radiotherapy and or chemotherapy may be at risk of premature ovarian insufficiency due to the effect of these treatments in reducing the ovarian reserve. The effect that the treatment has does depend on which treatment is used, over what duration and at what dose. As part of the complete care of women undergoing treatment for cancer should be offered discussion about the likely effects of treatment on future fertility and the potential fertility preservation options.
Options for fertility preservation include hormonal medications (gonadotrophin releasing hormone agnoists), ovarian tissue freezing and egg freezing. GnRH agonists cause a temporary suppression of ovarian function and a low estrogen state. One of the side effects can be to suppress menstruation and prevent heavy periods that may be associated with chemotherapy treatment and low blood counts. Women who have GnRh agonist treatment during chemotherapy, have better surrogate markers of fertility following treatment such as return of periods, antral follicle count and anti-mullerian hormone (AMH). The use of these medications in oncology patients is now subsidised making them readily accessible for women undergoing chemotherapy.
Ovarian tissue freezing involves taking a small portion of ovarian tissue and freezing strips of ovarian cortex. This involves having a keyhole surgery (laparoscopy) to remove the ovarian tissue and does carry the associated risks of surgery. The ovarian cortex strips are frozen with the hope that they may be reimplanted in the pelvis at a later stage and resume function to achieve a pregnancy. There is a risk of reintroducing cancerous cells along with the ovarian tissue so this is not a suitable treatment for all cancer types. It is an option however for women in whom egg freezing is not a suitable, feasible or preferred option.
Egg freezing remains the best established form of fertility preservation for women undergoing treatments which pose a risk to their ovarian function. Egg freezing involves giving hormone injections (gonadotrophins) to stimulate the ovaries to develop multiple follicles in a single cycle. Ultrasound and blood tests monitor the development of these follicles and determine the timing of the egg collection procedure. This requires a short anaesthetic and the eggs are collected under ultrasound guidance with a needle inserted through the wall of the vagina. There are some risks associated with this procedure. The collected eggs are then frozen for future use if required. The process of stimulating the ovaries can take around two weeks and sometimes the urgency of needing to start chemotherapy treatment does not allow time for this. Some women will have one, several, all or none of the treatments discussed here and counselling and treatment should be individualised to the woman and her wishes. This is an essential component of holistic cancer treatment both at diagnosis, through treatment and remission.