Clinical Practice Guidelines for Pregnancy-Associated Breast Cancer: Chinese Society of Breast Surgery (CSBrS) Practice Guidelines 2021
Pregnancy-associated breast cancer (PABC)—breast cancer diagnosed during pregnancy (BCP) or within 1 year after delivery (postpartum breast cancer, PBC)—presents a unique challenge: balancing life-saving cancer care for the mother with the safety of her developing fetus or newborn. In 2021, the Chinese Society of Breast Surgery (CSBrS) released evidence-based guidelines to help clinicians navigate this complex terrain, drawing on global research, expert consensus, and the specific needs of Chinese patients.
Who Developed the Guidelines?
Led by Dr. Qing Chen (Department of Breast Surgery, Fudan University Obstetrics and Gynecology Hospital) and Dr. Yi-Ran Qiu (Fudan University Shanghai Medical College), the guidelines were shaped by a 77-member voting committee. The group included 63 breast surgeons (81.8%), plus specialists in obstetrics, oncology, medical imaging, pathology, radiotherapy, and epidemiology—ensuring a multidisciplinary perspective. The target audience is clinicians specializing in breast diseases in China, but the principles are relevant to anyone involved in PABC care.
What Is PABC?
PABC encompasses two scenarios:
- Breast cancer during pregnancy (BCP): Diagnosed while a woman is pregnant.
- Postpartum breast cancer (PBC): Diagnosed within 1 year after giving birth.
For PBC, diagnosis and treatment follow the same rules as non-pregnancy-associated breast cancer—except for breastfeeding, which requires extra precautions. BCP, however, demands stricter safety measures to protect the fetus.
How Is PABC Diagnosed?
The CSBrS emphasizes that PBC diagnosis aligns with non-pregnancy breast cancer—but BCP requires fetus-friendly tools:
First-Line Screening for BCP
- Breast ultrasound: Recommended as the primary screening tool. Most Chinese women have dense breast tissue, which becomes even denser (and harder to image with mammography) during pregnancy due to glandular swelling. A 2009 WHO study confirmed ultrasound is safe for pregnant women.
- Core needle biopsy (CNB): The gold standard for confirming breast cancer in pregnant or lactating women. For lesions rated BI-RADS 4/5 (suspicious/malignant) or BI-RADS 3 with risk factors, CNB provides accurate histopathology without harming the fetus.
Checking for Distant Spread
To screen for metastases, the guidelines recommend abdominal ultrasound (safe and effective). Forbidden tests include radionuclide scans (e.g., PET scans) and CT scans—both carry radiation risks to the fetus, per the 2020 NCCN Oncology Guidelines. Breast MRI with gadolinium contrast is also prohibited: the contrast crosses the placenta and may cause birth defects.
How Is PABC Treated?
The core rule: Treat PABC like non-pregnancy breast cancer—but prioritize fetal safety.
Key Principles for BCP Treatment
- Second/third trimester care: For women in their second (14–27 weeks) or third (28+ weeks) trimester, cancer treatment can proceed without terminating pregnancy (termination does not improve survival). Early pregnancy (before 14 weeks) is riskier: surgery increases abortion risk, and chemotherapy causes birth defects in 20% of cases.
- Surgery options:
- Modified radical mastectomy: The standard procedure for BCP, supported by strong evidence.
- Breast-conserving therapy (BCT): Possible for stage I/II BCP (survival rates match mastectomy), but radiation—required after BCT—must wait until after delivery (radiation is forbidden during pregnancy).
- Forbidden therapies during pregnancy:
- Tamoxifen (endocrine therapy): Crosses the placenta and harms fetal development.
- Anti-HER2 targeted therapy (e.g., trastuzumab): Dangerous for the fetus.
- Radiation: Causes birth defects and childhood cancers.
Chemotherapy: Timing and Risks
Chemotherapy during pregnancy is only recommended when absolutely necessary—and only in the second or third trimester. Key rules:
- Stop chemo by 35 weeks or 3 weeks before delivery to avoid bleeding/infection risks during childbirth.
- Anthracycline-based regimens: Preferred (e.g., doxorubicin). Taxanes (e.g., paclitaxel) are supported by ESMO but caution is advised (NCCN notes limited safety data).
- Risks: Chemotherapy may cause preterm birth, low birth weight, or gestational hypertension. Close fetal monitoring (e.g., ultrasounds for growth) is essential.
PBC Surgery
For postpartum breast cancer, surgery follows non-pregnancy rules—but lactation changes breast shape, so clinicians must carefully consider BCT or reconstruction.
Breastfeeding and PABC
Breastfeeding is not recommended during:
- Chemotherapy: Drugs pass to the baby through breast milk.
- Endocrine therapy: Tamoxifen and other drugs harm infants.
- Targeted therapy: Anti-HER2 drugs are unsafe for nursing babies.
Key Considerations for Younger Patients
PABC patients are often younger—so genetic counseling is critical. Hereditary breast cancer (e.g., BRCA mutations) is more common in this group, which affects future fertility and family risk. Long-term follow-up is also essential:
- Monitor the mother for cancer recurrence.
- Track the child’s health (prenatal treatments may have delayed effects).
Final Notes
The CSBrS guidelines provide a clear, patient-centered framework for managing PABC—blending global evidence with the unique needs of Chinese women (e.g., dense breast tissue). For clinicians, the message is clear: Balance cancer care with fetal safety, use multidisciplinary teams (breast surgeons + obstetricians), and respect patient choices.
For patients and families, the guidelines underscore that PABC is treatable—but requires careful timing and collaboration.
Original Study: Chen Q, Qiu YR, Zhang MD, Zhu W, Gu WR, Wu KJ. Clinical practice guidelines for pregnancy-associated breast cancer: Chinese society of breast surgery (CSBrS) practice guidelines 2021. Chinese Medical Journal 2021;134:2395–2397. doi.org/10.1097/CM9.0000000000001686
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