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Dr Khoo Kei Siong, Deputy Medical Director at Parkway Cancer Centre, looks at how cancer and treatment can affect women’s fertility.

Can I conceive after being diagnosed with breast cancer? Many young patients ask doctors this question, and the simple, comforting answer is: “Yes”.

However, we would advise women not to conceive too soon after the diagnosis.  It is prudent to consider having a baby after the high-risk period, when cancer is more likely to recur, is over.

Most high-risk cancers recur within the first three years, so it would be advisable to wait a year or two before trying for a baby.

While it is always good to complete all treatments before getting pregnant, the age of the women and other considerations may not permit putting off pregnancy for many years.

For patients with hormone receptor-positive breast cancer, there is a need to take Tamoxifen for five to 10 years to reduce the risk of breast cancer recurrence. Delaying pregnancy for two to three years will allow them to benefit to some extent from the protective effect of Tamoxifen.

However, cancer treatment can affect fertility. Chemotherapy diminishes a woman’s ovarian reserves, which can lead to premature ovarian failure and menopause. It can also cause dryness of vaginal tissues, making intercourse painful and increasing the chances of vaginal infections. More generally, chemotherapy can cause fatigue, anxiety and hormonal swings, all of which may reduce sex drive.

Radiation therapy, which uses high-energy rays to target cancer cells, can also damage a woman’s ovaries, especially if it is targeted at the abdomen or pelvis area.

To preserve fertility, patients can explore options such as freezing their eggs, embryos, or ovarian tissue before undergoing treatment for their cancer.

Embryo cryopreservation is a well-established method of preserving a woman’s fertility and has success rates of between 30 and 50 per cent for each embryo transfer. If the patient is single, the eggs can be frozen by a method known as vitrification.

Harvesting the eggs for freezing, however, may take up to four weeks and it involves ovary stimulation.

There is concern about stimulating the ovaries to collect more eggs in women whose cancer is sensitive to hormones – as more than 50 per cent of breast cancers are. This is because stimulating the ovaries can cause high estrogen levels, which can potentially trigger the cancer to grow faster.

Other than freezing the eggs, the patient can also have her ovarian tissue cryopreserved. This involves surgically removing and freezing the ovary before beginning cancer treatment. After recovery from her treatment, the ovary is transplanted back when the patient is ready to conceive.

Another option is to give a medication known as GnRH agonist/antagonist, which essentially suppresses the function of the ovaries when the patient is undergoing chemotherapy. It protects the gonads by driving cells into a less active cell cycle stage, making them less sensitive to the damaging effects of chemotherapeutic agents.

This method has been shown to preserve fertility significantly; in one study, the rate of premature menopause dropped from 67 to 11 per cent.