Management of Cancer in Pregnancy

Diagnosis, staging, and treatment of cancer diagnosed during pregnancy — balancing maternal oncologic outcomes with fetal safety across all trimesters

Key Points

• Cancer complicates approximately 1 in 1,000 pregnancies; the most common are breast cancer, cervical cancer, hematologic malignancies (Hodgkin lymphoma, non-Hodgkin lymphoma, leukemia), melanoma, and colorectal cancer.
• Diagnosis is often delayed in pregnancy because symptoms overlap with normal pregnancy changes — a palpable mass, abnormal bleeding, or persistent symptoms should never be dismissed as pregnancy-related without evaluation.
• Most chemotherapy agents — particularly anthracyclines and platinum agents — can be safely administered after the first trimester (after organogenesis, ≥14 weeks); first-trimester chemotherapy carries high risk of fetal loss and major malformations and should generally be avoided.
• Certain agents are contraindicated throughout all trimesters regardless of gestational age: methotrexate, 5-fluorouracil (systemic), vinca alkaloids in high doses, bleomycin, and nearly all targeted agents and checkpoint inhibitors.
• Imaging during pregnancy should use the lowest effective radiation dose; MRI (without gadolinium in the first trimester) and ultrasound are preferred; CT scanning may be used when clinically necessary as fetal radiation doses from most diagnostic CT scans are below the threshold for deterministic effects (100–200 mGy).
• Delivery timing, mode, and neonatal considerations must be planned multidisciplinarily; chemotherapy should not be administered within 3–4 weeks of anticipated delivery to prevent neonatal myelosuppression from transplacental drug transfer.

Epidemiology, Diagnosis, and Multidisciplinary Framework

**Incidence and cancer types:** Cancer in pregnancy is uncommon but not rare — approximately 1 in 1,000 pregnancies in the United States. As childbearing age rises, the incidence is increasing. The most common cancers diagnosed during pregnancy: 1. **Breast cancer**: most common; ~1 in 3,000 pregnancies; often detected later due to physiologic breast changes of pregnancy masking masses 2. **Cervical cancer**: second most common; often detected on Pap smear at prenatal visit 3. **Hodgkin lymphoma**: most common hematologic malignancy in pregnancy; typically HL classic type 4. **Melanoma**:…

Imaging During Pregnancy

Appropriate imaging must not be withheld due to pregnancy — delayed staging leads to suboptimal oncologic management. The goal is to use the lowest effective dose while obtaining clinically necessary information. **Radiation-free modalities — always preferred:** *Ultrasound:* - No ionizing radiation; no known fetal harm at diagnostic frequencies - First-line for breast, pelvic, abdominal, lymph node evaluation - Limited for thoracic staging, bony metastases, and deep retroperitoneal structures *MRI:* - No ionizing radiation; extensive safety data in pregnancy - Preferred cross-sectional…

Chemotherapy in Pregnancy

**First trimester (0–13 weeks) — generally contraindicated:** Organogenesis (formation of all major organ systems) occurs primarily between weeks 5 and 12. Cytotoxic chemotherapy during this window carries: - 10–20% risk of major fetal malformation - Increased risk of spontaneous abortion and fetal death - Most chemotherapy drugs are teratogenic in animal models and/or have documented human fetal toxicity in the first trimester Therapeutic termination of pregnancy may be discussed in cases requiring urgent chemotherapy (e.g., aggressive AML, rapidly progressive lymphoma) in the first…

Radiotherapy and Surgery During Pregnancy

**Radiotherapy in pregnancy:** Radiotherapy can be used in pregnancy when the target volume is distant from the uterus and fetal dose can be kept to acceptable levels. *When radiotherapy can proceed during pregnancy:* - Cranial radiation (brain metastases or primary brain tumor): fetal dose from scatter and leakage is typically <50 mGy — generally acceptable in 2nd/3rd trimester - Supradiaphragmatic radiation (Hodgkin lymphoma, mediastinal): with careful shielding, fetal dose may be kept <100 mGy, particularly in early 2nd trimester; individualized dosimetry calculation required - Breast…

Specific Cancers in Pregnancy

**Breast cancer:** Most common cancer in pregnancy. Pregnancy-associated breast cancer (PABC) is defined as breast cancer diagnosed during pregnancy or within 1 year postpartum. PABC often presents at a more advanced stage because: - Breast examination is less sensitive (engorgement) - Clinicians and patients attribute masses to pregnancy changes - Biopsy may be deferred Key management principles: core needle biopsy is safe; ultrasound-guided preferred; MRI (without gadolinium in 1st trimester) for locoregional staging; sentinel lymph node biopsy with Tc-99m safe after 1st trimester; AC or…

Delivery Planning and Neonatal Considerations

**Timing of delivery:** - The goal is to allow the pregnancy to reach as close to term (37–40 weeks) as possible while ensuring adequate maternal oncologic management - Pre-term delivery should only be considered when: a. Oncologic urgency requires treatment that cannot be safely administered during pregnancy (e.g., pelvic radiation, contraindicated agents) b. Fetal maturity is established (≥34 weeks with favorable lung maturity) c. Maternal condition is deteriorating in a way that necessitates delivery - Fetal lung maturity: consider antenatal corticosteroids (betamethasone) if preterm…