WEBSITE (THE CONVERSATION): Former Alone Australia winner Gina Chick was diagnosed with breast cancer just days after finding out she was pregnant. She describes in her recent book her experience with chemotherapy and what happened afterward.
Thankfully, a cancer diagnosis during pregnancy and in the year after birth is rare. But such cases are becoming more common in many parts of the world. Researchers aren’t sure exactly why.
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Here’s what researchers know so far and the treatment options.
A study in New South Wales found that in 1994 there were approximately 94 cancer diagnoses during pregnancy or within one year of giving birth per 100,000 women who gave birth. This number increased to around 163 per 100,000 in 2013. Although these statistics are more than 10 years old, they are the latest and most rigorous data available in Australia.
A Swedish study of pregnancies from 1973-2017 had similar results.
Both studies found that about a quarter of pregnancy-related cancers were diagnosed before birth, with the remainder diagnosed in the year after birth.
The UK’s first comprehensive review of cancer during pregnancy looked at diagnoses in 2016-2020.
This study, the NSW study and others have found that breast cancer and skin cancer (usually melanoma) are the most common cancers associated with pregnancy. This group also has high rates of thyroid, gynecological (especially cervical and ovarian) and leukemia cancers.
British research shows that about 92% of cancers are new diagnoses and about 82% are symptomatic. The majority (81%) were treated with curative intent, and approximately 82% of pregnancies associated with a cancer diagnosis resulted in live birth.
However, 20% of mothers died by the end of the five-year study period. Gastrointestinal (bowel) cancer is especially worrisome. They have the highest mortality rate of about 46% and are diagnosed at more advanced stages of cancer.
This may be because many symptoms of gastrointestinal cancer such as abdominal pain, fatigue and acid reflux overlap with symptoms of pregnancy. In other words, some cancer symptoms can be confused with pregnancy symptoms, “masking” or delaying a cancer diagnosis.
The wide range of cancers that appear during and after pregnancy suggests that there are many contributing factors.
In high socioeconomic countries, women are having children later, and the biggest risk factor for many cancers is increasing age. However, the evidence that age is a major factor in pregnancy-related cancers is inconclusive. This may explain some but not all cases.
Another factor may be the increased use of prenatal genetic screening tests during early pregnancy. They analyze DNA derived from the mother’s blood to detect chromosomal abnormalities in the developing fetus. But these tests can also provide information about the mother’s chromosomes. This has led to the diagnosis of Hodgkin’s disease, breast cancer, and colorectal cancer in pregnant women without symptoms.
Estrogen and progesterone are two hormones important for the growth and development of breast tissue and support other aspects of a healthy pregnancy. These can also contribute to the development of cancer, especially breast cancer. However, it is unclear whether this is linked to increased rates of pregnancy-related cancers.
Other cancers, such as skin cancer, are linked to environmental factors such as UV exposure. Notably, melanoma was the leading pregnancy-related cancer in the NSW study, reflecting high rates of skin cancer in the local population. Other environmental factors, such as smoking and human papilloma virus, have been linked to cervical cancer. Again, we are not sure whether those factors are associated with increased rates of pregnancy-related cancers.
Pregnancy further complicates cancer diagnosis, as any potential treatment for the mother could jeopardize the health and survival of the fetus. Therefore, some aspects of treatment may need to be adjusted.
Surgery can usually be performed in any trimester depending on the location of the cancer.
Radiation therapy requires careful planning because the effects of radiation on the fetus depend on the stage of development, where the radiation is introduced into the body, and the dose.
Chemotherapy should be avoided in the first trimester because it can be toxic to the fetus. But it can usually be given in the second and third trimesters. Chemotherapy should be avoided within three weeks after birth to reduce the risk of bleeding and infection in newborns, who may also have a weakened immune system due to chemotherapy.
Targeted immunotherapies are often given to the mother after childbirth. Depending on her treatment, she may be advised not to breastfeed. That’s because the medicine can pass from mother through breast milk to baby.
Reassuringly, NSW data found no increase in the rate of babies dying during birth if they were born to mothers with pregnancy-related cancer.
However, there are more planned preterm births. This is because women are offered induction of labor and/or cesarean section to facilitate the mother’s cancer treatment, while reducing treatment-related risks to the fetus.
There were also higher rates of low birth weight and low Apgar scores (an indicator of a baby’s condition immediately after birth) – which may be linked to premature birth.
We have much to learn about the causes behind the increasing rates of pregnancy-related cancers and what women diagnosed with these cancers can expect.
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We also need to combine cancer and obstetrics data in national databases. This will allow us to know which areas need to be prioritized for further research, provide clinical guidelines for cancer screening during and after pregnancy, and help assess response to treatments. future screening or therapy program.