Pregnancy-Associated Breast Cancer (PABC) is defined as breast cancer diagnosed during gestation or within the first year following delivery. This diagnosis is rare, occurring in approximately one out of every 3,000 pregnancies. Managing this disease requires a careful, multidisciplinary approach that balances the need for prompt, effective cancer therapy for the mother with the safety of the developing fetus.
Unique Challenges in Detection During Pregnancy
The physiological changes in the breast during pregnancy often complicate and delay tumor detection. Breasts become enlarged, tender, and dense, which can mask a new mass and make self-examinations less reliable. A palpable mass persisting longer than two weeks should be investigated, though most breast biopsies performed during pregnancy are benign.
Specialized diagnostic methods are used to ensure fetal safety. Ultrasound is the primary and safest imaging modality, as it uses no radiation and distinguishes between a fluid-filled cyst and a solid mass. Mammography is considered safe when needed, provided the abdomen is shielded with a lead apron to minimize fetal radiation exposure. Core needle biopsy is the standard procedure for obtaining a tissue sample and is safe at any stage of pregnancy. Magnetic resonance imaging (MRI) is less common because the contrast material, gadolinium, is generally avoided as it can cross the placenta.
Tailoring Treatment Strategies Based on Trimester
Management of breast cancer during pregnancy is highly customized and depends heavily on the fetus’s gestational age. A team of specialists, including oncologists, obstetricians, and maternal-fetal medicine experts, collaborates to create a treatment plan. The guiding principle is to provide the mother with effective cancer treatment while minimizing risk to the fetus.
Surgery is one of the most consistently safe treatment options and can be performed in all trimesters. A mastectomy, which removes the entire breast, is often preferred, especially if the diagnosis is made in the first trimester. This is because a lumpectomy typically requires follow-up radiation, which must be delayed until after delivery. If the patient is diagnosed in the second or third trimester, a lumpectomy can be considered, with the understanding that radiation therapy will be postponed.
Chemotherapy is contraindicated during the first trimester (the period of organogenesis) due to the high risk of birth defects or miscarriage. However, it can be safely administered during the second and third trimesters, as the fetus is more developed and the placenta acts as a protective barrier against many drugs. Common chemotherapy regimens, such as those containing anthracyclines and taxanes, are often used. Chemotherapy is typically discontinued around the 34th or 35th week of gestation to protect the baby from the mother’s lowest blood cell count period.
Radiation therapy and hormone therapy are generally avoided throughout the entire pregnancy. Radiation directed at the breast carries a risk of exposing the fetus to radiation, which can cause harm. Hormone therapies, such as tamoxifen or aromatase inhibitors, are also held until after delivery because they can interfere with fetal development. If the mother is close to term, labor may be induced a few weeks early to allow the full course of treatment, including delayed radiation, to begin sooner.
Prognosis and Tumor Biology
Pregnancy-associated breast cancer is frequently diagnosed at a later stage compared to breast cancer in non-pregnant women. This delay occurs because the normal changes of pregnancy can obscure symptoms, and routine screening mammography is often deferred. As a result, the cancer is more likely to have spread to the lymph nodes at the time of diagnosis.
PABC tumors often exhibit more aggressive biological characteristics than breast cancers diagnosed in non-pregnant, age-matched women. They are frequently characterized as estrogen-receptor negative, progesterone-receptor negative, and may have higher rates of the challenging triple-negative or HER2-positive subtypes. The hormonal and biological environment of pregnancy, particularly the breast tissue changes that occur during the postpartum period, is thought to contribute to this increased aggressiveness.
While the prognosis for PABC has improved, the disease is still associated with a generally poorer survival rate compared to breast cancer that is not pregnancy-related. However, some studies suggest that when PABC patients are carefully matched with controls based on age, tumor stage, and other factors, the outcomes may be similar. The poorest prognosis appears to be linked to diagnoses made in the second and third trimesters or shortly after delivery.
Postpartum Care and Future Reproductive Concerns
Once the baby is delivered, the focus shifts to completing the full course of cancer therapy that was paused or delayed. Radiation therapy is often the first step following an earlier lumpectomy, and any necessary hormone or targeted therapy is initiated.
Breastfeeding is generally discouraged on the affected side, especially following surgery or if radiation therapy is scheduled. Furthermore, breastfeeding must be avoided if the mother is receiving chemotherapy or hormone therapy, as these drugs can pass into the breast milk and harm the infant. Patients must consult closely with their oncologist and pediatrician regarding safety.
Long-term concerns include fertility, future pregnancies, and the risk of recurrence. Many women who have undergone treatment for breast cancer, including those receiving chemotherapy, can still conceive naturally, though fertility preservation may be chosen beforehand. Studies generally show that subsequent pregnancies after breast cancer treatment do not increase the risk of recurrence. Physicians typically recommend waiting at least two to five years after treatment is complete before attempting another pregnancy.