Everything you need to know about pregnancy-associated breast cancer

Dr Fatima Hoosain is a specialist surgeon at Apffelstaedt & Associates with a particular interest in breast and thyroid health. Here, she speaks about pregnancy-associated breast cancer, sharing information on the risks, treatment and what it all means for the baby.

Pregnancy-associated breast cancer (PABC) is defined as breast cancer diagnosed during pregnancy or in the first postpartum year.

Breast cancer is the second most common malignancy affecting pregnancy, but pregnancy-associated breast cancer is an extremely rare event with multiple contributing factors. It affects approximately 1 in 3000 pregnant women and predominantly in women aged 32- 38 years of age.

With increasing rates of breast cancer and with more women delaying childbearing, it is likely that the rates of pregnancy-associated breast cancer will increase.

Read: Preeclampsia | Signs, symptoms and causes during pregnancy

What are the risk factors for developing PABC?

  • Genetic mutations such as the BRCA mutation – 33% of cancers in patients under the age of 20 and 22% of cancers in patients between the ages of 20-40 are related to genetic mutations
  • Alcohol
  • Smoking
  • Prior radiation exposure

How is a PABC diagnosed?

Breast cancer in pregnancy, like most breast cancers in patients under the age of 40 years, is usually diagnosed on physical examination of a palpable mass within the breast or axilla.

Because breast cancer is detected in this way, it is often seen later than those detected by routine screening.

To further complicate the matter, a breast cancer diagnosis is often delayed due to overlapping pregnancy-induced breast changes, such as engorgement, making it difficult to discern a concerning breast mass from a normal breast in a pregnant woman.

Also read: How one woman’s traumatic experience drove her investigation into pregnancy and mental health

How is a PABC evaluated?

A breast ultrasound can be done to characterise the clinically palpable mass further. This will further evaluate the lesion for any suspicious features, as 80% of breast masses identified during pregnancy represent benign pathology.

Furthermore, if a suspicious lesion is found on ultrasound, it can be biopsied under ultrasound guidance. A mammogram can also be done during pregnancy.

Still, the sensitivity of a mammogram in women under the age of 40 is low due to the increased parenchyma density of the young breast tissue. The patient must be counselled about the radiation exposure if this examination route is to be pursued.

Breast cancer in pregnant women is often diagnosed at a more advanced stage than screening-detected breast cancer. Therefore, the patient will usually require further investigation to evaluate for metastasis.

Where does breast cancer metastasis, and how do we evaluate for it?

The most common sites for breast cancer metastases in the lung, liver and bone.

During pregnancy, lung metastasis may be evaluated using a chest X-ray which can be regarded as safe if there is adequate abdominal shielding. The liver metastases can be evaluated using an abdominal ultrasound.

Bone metastases are usually evaluated with a bone scan outside of the pregnancy situation. Still, due to the toxic effects of the radioactive technetium on the developing foetus, an MRI is the preferred examination to look for bone metastases.

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What are the treatment options for PABC?

The most critical factor in planning treatment is not to delay it. If the patient is close to the delivery date, it may be appropriate to postpone treatment until after the delivery.

Termination of pregnancy in the 1st or 2nd trimester has not been shown to improve prognosis. Surgery is the first-line treatment for the operable disease, and a modified radical mastectomy is the surgery of choice. The risk of surgery is from general anaesthesia and is highest during the first trimester.

Radiation therapy is, in general, contraindicated in pregnancy due to an increased risk of foetal malformations and associated delays in neurocognitive development.

For this reason, most pregnant women undergo mastectomy as first-line therapy. Chemotherapy as an additional treatment has also been beneficial in patients with high-risk breast cancer.

Chemotherapy is contraindicated during the first trimester due to its teratogenic risk during organogenesis. Teratogens are drugs, chemicals, or even infections that can cause abnormal foetal development.

Organogenesis is the phase of embryonic development that starts at the end of gastrulation and continues until birth. Methotrexate, trastuzumab and tamoxifen are currently contraindicated in pregnancy.

Must see: How amniotic fluid protects you and your baby in pregnancy | Nature’s beautiful safety nets

Are there recommendations regarding foetal surveillance?

The recommendations suggest growth scans every four weeks, as preterm labour and intrauterine growth restriction (IUGR) are risks of chemotherapy during pregnancy, including a detailed anatomy scan (to assess for foetal anomalies if the foetus has been exposed to medication in the first trimester.

If IUGR is noted, then more frequent evaluation and the addition of Doppler examination and amniotic fluid measurement should be considered.

When should the baby be delivered?

Delivery should occur at term or as close to term as possible. Induction of labour is only indicated to provide treatment to the mother that is contraindicated during pregnancy.

There is also no risk of breast cancer metastases to the foetus as the cancer cells cannot cross the placental barrier.

Can I breastfeed?

Lactation and breastfeeding are not contraindicated unless the patient is receiving chemotherapy or radiation therapy, in which case the breast milk will contain the administered agent.


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