March 21, 2023
People preserve their fertility through egg freezing for many reasons. The most common reason a person would freeze eggs is because they are single in their 30s and are aware of the harmful impact of age on egg health. They freeze them so they might have younger eggs to use when they are older.
Another reason people will freeze their eggs is cancer treatment. Several cancers can strike young people and the cancer itself, or it’s treatment can harm their eggs. Breast cancer is an example that, sadly, we see all too often in women before they have had children. Nearly 20% of breast cancers occur in women under age 45. If the breast cancer needs to be treated with chemo therapy, there is a risk the eggs will be harmed both in count and quality. So, many women every year who are diagnosed with breast cancer will opt to freeze their eggs.
I have been talking to these women with newly diagnosed breast cancer for nearly 2 decades about the pros and cons of egg freezing.
Worry over the impact of the treatment on the cancer has always been on my mind. We know many breast cancers are sensitive to hormones like estrogen and progesterone. During egg freezing we increase a person’s levels of these hormones dramatically. We will often use letrozole during the egg stimulation phase to decrease the rise in estrogen but ultimately it is elevated beyond normal menstrual cycle levels. Are we providing fuel for cancer growth? Are we doing more harm than good?
There have been several small studies that have reassured us that likely we are not providing harm. That we are not increasing the growth or spread of the cancer. This month though we finally got a large studying that nicely compares two groups of breast cancer patients: those who froze (mature) eggs with medications and those who froze (immature eggs) with no medications.
Side note: Freezing immature eggs requires in vitro maturation (IVM) which has a much lower pregnancy rate than freezing stimulated mature eggs so the group who took medications will have a higher success rate from egg freezing than those who did not.
The study was published in Fertility and Sterility and examined 740 women: about half having medications/ovarian stimulation and the other half having no medications.
There was no difference in breast cancer recurrence or disease - freeze survival in the two groups at about 5 years of follow-up.
This study will help us better inform (and reassure!) breast cancer patients, who already have so many worries when the see us, about the pros and cons of egg freezing before chemotherapy for breast cancer.
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