Breast cancer diagnosed during pregnancy (BCP) is rare but increasingly common, and new research shows that most modern breast cancer treatments can be safely adapted for pregnant patients. An international panel of experts reviewed the latest evidence and concluded that treatment during pregnancy should be the first option, closely mirroring the care given to nonpregnant young women whenever possible. While chemotherapy must be avoided in the first trimester, most other treatments—including surgery, sentinel lymph node biopsy, taxane-based chemotherapy, platinum agents, and dose-dense regimens—can be given safely in the second and third trimesters after careful risk/benefit assessment. The panel emphasizes that premature delivery should be avoided whenever possible, and that delaying or omitting chemotherapy may actually increase the risk of cancer relapse.
Breast cancer diagnosed during pregnancy (BCP) is a rare and emotionally overwhelming situation, but recent years have brought important news: awareness of treatment options has grown, and more intensive breast cancer treatment is now being offered during pregnancy than ever before. Guidelines for diagnosing and treating BCP were first published in 2006 and updated in 2010, and they carry a clear message: treatment during pregnancy should be the first option, not termination of pregnancy or delayed therapy.
An international group of specialists—including members of the German Cancer Society (DKG) breast cancer guideline consortium, the International Network on Cancer and Infertility in Pregnancy (INCIP) of the European Society of Gynecologic Oncology, and experts in breast cancer and placental research—convened to review the latest scientific literature. Their goal was to answer a specific question: how can recent advances in breast cancer care, including the use of carboplatin, dose-dense chemotherapy, trastuzumab, neoadjuvant therapy, and sentinel lymph node biopsy, be safely adapted for pregnant patients?
The answer, published in JAMA Oncology, is reassuring to many patients: the majority of women diagnosed with breast cancer during pregnancy can and should receive treatment during the pregnancy, with premature delivery avoided whenever possible.
Breast cancer is one of the most common malignant tumors diagnosed during pregnancy. Although BCP remains rare overall, its incidence has been increasing steadily over the past few decades. Maternal age has been rising in developed countries since the 1970s—and subsequently in several developing countries—which, combined with the upward trend of breast cancer incidence and the postponement of childbearing, has led to more cases of BCP.
The numbers are striking: approximately 1 in 5 breast cancers diagnosed in women aged 25 to 29 years is associated with pregnancy, meaning the cancer is diagnosed either during pregnancy or within the first postpartum year. Population-based studies report that the occurrence of breast cancer diagnosed during pregnancy ranges from 2.4 to 7.3 per 100,000 pregnancies.
A Danish study found that 81% of pregnancies affected by breast cancer were terminated during the first trimester, while other reports found that only 19% of all BCP cases were diagnosed in the first trimester. Delayed diagnosis is a likely explanation for this discrepancy—many cases are simply not detected until later in the pregnancy or after delivery.
Breast cancer during pregnancy generally presents at more advanced stages compared to breast cancer in nonpregnant women, and this has historically raised concerns about worse outcomes. However, the evidence tells a more nuanced story.
Several earlier studies produced inconsistent results, largely because they included only small numbers of patients. The largest cohort study to date included 313 patients and, after carefully controlling for cancer stage, prognostic factors, and adjuvant treatment, found that survival was similar for patients with BCP versus nonpregnant patients with breast cancer.
Importantly, unlike breast cancer diagnosed during the first year after delivery, a diagnosis of breast cancer during pregnancy does not appear to be an independent poor prognostic factor—provided that standard treatment is administered. Despite possible pharmacokinetic changes (how the body processes chemotherapy drugs), survival rates did not differ between patients who received chemotherapy during pregnancy versus those who received it after delivery. This means that pregnant patients who receive appropriate, timely treatment can expect outcomes comparable to young nonpregnant patients.
The general recommendations for diagnosing BCP have not changed since 2010, but there are important details every pregnant patient should understand. One key principle: all palpable breast masses require imaging and imaging-guided biopsy without delay. No woman should be told to "wait and see" simply because she is pregnant.
Breast ultrasound and mammography can be safely and effectively performed during pregnancy. Bilateral mammography (imaging both breasts) is recommended in all women with a confirmed or highly suspicious malignant lesion.
The radiation dose from a mammogram is less than 3 mGy (that's 3 milligray, a measurement of absorbed radiation), which corresponds to approximately 7 weeks of exposure to natural background radiation. The estimated dose to the uterus and fetus is less than 0.03 μGy—an extremely small amount. For context, the threshold for negative effects of radiation on the fetus is approximately 100 mGy, with some uncertainty at doses between 50 and 100 mGy. That means a mammogram delivers less than one-three-thousandth of the dose known to cause harm.
Despite these reassuring numbers, many patients and physicians still worry about radiation safety. The authors emphasize that this concern should be discussed openly with the patient. They also note that maternal and fetal radiation exposure depends on gestational age, the anatomic site being imaged, the imaging modality, and technique.
Contrast-enhanced magnetic resonance imaging (MRI) is not recommended during pregnancy because the use of iodinated and gadolinium-based contrast agents has not been sufficiently studied in pregnant women. Similarly, whole-body MRI has not been studied enough in breast cancer in general, and although pharmacologic agents used for diagnostic nuclear medicine and positron-emission tomography (PET) probably do not result in radiation exposure exceeding 50 mGy, their use is not recommended during pregnancy. Imaging and staging procedures should only be performed in advanced stages in which they might alter treatment decisions.
The gold standard for diagnosing BCP is a core biopsy (removing a small sample of tissue with a needle) of the suspicious lesion. The pathologist who examines the tissue must be informed about the pregnancy, as this can affect interpretation.
Overall, the histological features of BCP tumors do not differ from those in young nonpregnant women with breast cancer. Almost all BCP tumors are ductal invasive (starting in the milk ducts and spreading outward), mainly hormone receptor–negative and undifferentiated (meaning the cancer cells look very abnormal and grow aggressively).
In general, tumor mutations do not differ between pregnant and nonpregnant young women, although small studies have shown significant differences in gene expression analyses. The authors caution that no definite conclusions for everyday clinical practice can be drawn from these analyses yet. A major challenge for future research is choosing the right control group—matching cohorts by treatment, histologic subtype, and age is essential.
Taking a family history is a prerequisite for any breast cancer patient, and genetic counseling should be offered according to national guidelines, which differ substantially between countries. BRCA testing is becoming treatment-relevant, especially because the majority of BCP cases are triple-negative breast cancer (TNBC)—a subtype that lacks estrogen receptors, progesterone receptors, and HER2 amplification.
Here is a number that matters for young patients: in young patients with TNBC, the probability of detecting a germline BRCA mutation is approximately 20%. This means that one in five young women with this breast cancer subtype carries an inherited genetic mutation that could have implications not only for her own treatment but also for future family planning and relatives' cancer risk.
In general, the surgical approach for pregnant patients is the same as for nonpregnant patients. Mastectomy is not recommended solely on the basis of pregnancy or because of a possible consequent delay of radiation therapy (RT). Breast-conserving surgery (removing only the tumor and a margin of surrounding tissue) is a valid option when appropriate.
Immediate breast reconstruction after mastectomy is an essential component of treatment for breast cancer patients, particularly for young women. Based on a single published experience, tissue expander insertion appears to ensure a short operation time and does not seem to be associated with considerable harm to the mother or the fetus. Therefore, this surgical technique could be considered in the multidisciplinary treatment of women diagnosed with breast cancer during pregnancy.
However, more complex reconstruction, such as flap reconstruction (using tissue from other parts of the body), is not a standard option during pregnancy. One important practical reason: breast size differs between pregnant and nonpregnant states, so reconstruction performed during pregnancy may not produce optimal long-term cosmetic results.
The sentinel lymph node is the first lymph node to which cancer cells are likely to spread. Checking this node helps doctors determine whether the cancer has spread, without removing all the lymph nodes in the armpit. Recommendations from the American Society of Clinical Oncology (ASCO) historically stated that pregnant patients should not undergo SLNB, based on older cohort studies and informal consensus. But the evidence has evolved.
Studies now show that SLNB can be safely performed during pregnancy. The procedure uses small amounts of injected radioactive material that stays mostly at the injection site, which is shortly afterward removed surgically. The radiation doses absorbed by the fetus are mostly less than 20 μGy for 10 to 20 MBq (megabecquerels, the unit of radioactivity)—roughly 1 μGy per MBq, as measured in experimental studies and Medical Internal Radiation Dose Committee models.
From a maternal oncologic point of view, SLNB appears to be accurate and safe, with only 1 unsuccessful mapping and 1 recurrence among 97 patients with BCP. Pregnant patients should be offered SLNB rather than full axillary lymph node clearance whenever it is indicated according to general practice for nonpregnant patients.
Practical recommendations for pregnant patients receiving SLNB:
In one small series of 25 women who underwent SLNB during pregnancy, 7 received blue dye for mapping. The authors note that blue dye is not recommended even outside pregnancy as a sole procedure, so avoiding it in pregnant patients is consistent with best practice.
Radiation therapy during pregnancy is rarely indicated for BCP. In general, the recommendation is to postpone RT until after delivery. The available information on long-term consequences of radiation exposure in the womb is limited, and two factors must be weighed: the dose to the fetus and the risk that radiation exposure causes adverse effects.
Understanding radiation risk requires distinguishing between two types of effects:
If radiation occurs in very early pregnancy (often before the pregnancy is diagnosed), it generally leads to spontaneous abortion. From the third week of pregnancy onward, malformations can occur. Radiation exposure may also affect the developing central nervous system, potentially causing neuropsychological and behavioral dysfunction.
The reassuring data point: at low doses, the incidence of childhood cancer and leukemia (naturally 0.2% to 0.3% for ages 0 to 15 years) does not appear to be increased. Following a dose of 10 mGy, the relative risk rises to 1.4—still a very low absolute risk. Radiation's effect on germline mutations in eggs (oocytes) has not been shown to cause negative effects in humans.
The radiation dose received by the fetus depends on the distance between the radiation field and the position of the fetus (which changes with gestational age), the amount of radiation leakage outside the field, and the use of effective shielding, which can reduce the dose by 50% to 75%. During the first months of pregnancy, the uterus does not extend outside the true pelvis, and with appropriate techniques and shielding, the dose to the fetus will be only 0.1% to 0.3% of the prescribed dose to the breast—resulting in a very low risk of inducing malformations.
Several case reports describe radiation therapy administered for BCP with low fetal doses and healthy babies delivered. Therefore, RT might be considered in the first or early second trimester if the risk of delaying or omitting RT is believed to outweigh the risk of harming the fetus. In practice, this is a deeply individualized decision that should be made by the entire care team with the patient.
This is the most detailed and clinically important section of the review. The overarching principle: treat pregnant patients with BCP during the second and third trimester, following guidelines for nonpregnant young patients as closely as possible.
First trimester warning. Chemotherapy is contraindicated during the first trimester because of a higher risk of inducing fetal malformations. The US National Toxicology Program monograph reports a prevalence of malformations of 14% if chemotherapy is given in the first trimester, declining to 3% if chemotherapy is applied later in pregnancy. For comparison, the reported rate of major malformations in the general population is approximately 3% in the United States and 6.7% in a German registry. This means that chemotherapy in the second and third trimester carries no higher risk of major birth defects than the background rate in the general population.
Why not wait until after delivery? Postponing chemotherapy until after delivery might seem like a safe option, but data in nonpregnant young women indicate that delaying or postponing chemotherapy might increase the risk of relapse. This is why the recommendation is to treat during pregnancy rather than wait.
Which drugs are safe and recommended? The standard adjuvant (post-surgery) or neoadjuvant (pre-surgery) combination recommended for nonpregnant patients includes:
One of the most widely used regimens—also used during pregnancy—is epirubicin hydrochloride plus cyclophosphamide, followed by weekly paclitaxel. The reverse sequence (starting with a taxane) is also possible; the decision may be based on gestational age and other clinical factors.
Fluorouracil is no longer indicated for breast cancer therapy because it does not add any benefit to an anthracycline-taxane–based regimen.
Platinum agents (carboplatin). Platinum derivatives may play a role in treating patients with triple-negative breast cancer. Neoadjuvant trials demonstrated significantly higher pathological complete response rates (meaning no cancer cells remain in the removed tissue) when carboplatin was added, although survival data are still immature. Carboplatin therapy may be considered during the second and third trimesters of pregnancy. It remains unclear which platinum drug is most effective, but carboplatin may have less overall toxicity than cisplatin.
Dose-dense regimens. Dose-dense chemotherapy (the same dose given over a shorter interval, such as every 2 weeks instead of every 3 weeks) leads to better survival than conventionally dosed regimens, especially in high-risk patients. Dose-dense chemotherapy appears to be an acceptable option during pregnancy. However, intensified dose-dense (IDD) chemotherapy—a higher dose over a shorter interval—has not been studied systematically in pregnancy. The high rate of grade 2 to 4 anemia (59%), with need for transfusion in 28% of patients, and the high risk of febrile neutropenia (7% despite primary G-CSF prophylaxis) mandate a strict risk/benefit analysis. IDD cannot generally be recommended in BCP.
Pregnancy causes significant physiological changes that affect how drugs move through the body. An increased activity of major enzymes involved in the metabolism of taxanes and anthracyclines—including cytochrome P450 isoforms such as CYP3A4 and CYP2C8—has been observed in the late trimesters of pregnancy, potentially resulting in decreased drug exposure. Because albumin concentrations (blood proteins that bind to drugs) also vary significantly during pregnancy, and taxanes are highly protein-bound, this can lead to significant changes in taxane pharmacokinetics.
Pharmacokinetic data comparing anthracyclines and taxanes in pregnant versus nonpregnant patients showed that taxane serum levels were significantly decreased during pregnancy, especially for paclitaxel. Conversely, exposure to anthracyclines was not significantly modified by pregnancy.
So should doses be increased? The authors say no, for several important reasons:
Standard practice is to dose according to actual body weight and avoid underdosing. On the basis of 11 reported cases without outcome data, increasing the dose cannot be recommended.
Data on transplacental transfer (how much drug crosses from mother to baby) are reassuring for both anthracyclines and taxanes, though there is marked variability between patients, particularly with docetaxel. For fetal safety, paclitaxel should probably be preferred over docetaxel in pregnant patients. Significant transplacental transfer of carboplatin has been demonstrated, and long-term data from the children exposed in the womb remain limited.
One finding that deserves attention: a significantly higher incidence of small-for-gestational-age neonates is observed when chemotherapy is given during pregnancy. This suggests chemotherapy may have a toxic influence on placental development, leading to placental malfunction—for example, through incomplete trophoblast invasion into the uterus, resulting in decreased transfer of nutrients to the fetus. Organogenesis (the formation of organs) is complete at approximately the 10th week of gestation, which is why chemotherapy can be considered from that point onward. However, trophoblast invasion of the placenta is not completed until approximately week 20—so starting chemotherapy at week 14 might interfere with the later stages of placental development.
Trastuzumab (Herceptin) is an integral part of primary treatment for women with HER2-positive breast cancer. In nonpregnant patients, starting trastuzumab as early as possible—and combining it with chemotherapy rather than giving it sequentially—is associated with better long-term outcomes.
However, trastuzumab is generally not recommended during pregnancy due to its potential fetal toxicity. In a recent review, the authors identified 18 reports in the literature of using trastuzumab during pregnancy. The key concerns are fetal toxicity and a condition called oligohydramnios (low amniotic fluid) or anhydramnios (absence of amniotic fluid), which can severely affect fetal development.
A careful risk/benefit analysis needs to be discussed with the patient, since the early start of trastuzumab improves survival but may harm the fetus. There are no data for pertuzumab (another HER2-targeted drug) during pregnancy, so its use is not recommended. Endocrine treatments (such as tamoxifen or aromatase inhibitors) are also not indicated during pregnancy. For women who require these agents, treatment is typically deferred until after delivery.
The central message of this review is hopeful: a breast cancer diagnosis during pregnancy is no longer a reason to terminate the pregnancy or to delay all cancer treatment. The international expert panel's updated recommendations can be summarized as follows:
This is a narrative review, not a randomized controlled trial. The authors note several important limitations:
The authors call for a multidisciplinary approach involving breast cancer specialists, maternal-fetal medicine experts, pathologists, and neonatologists. They also urge systematic data collection whenever possible, so that each case can contribute to the growing body of knowledge about BCP.
For patients facing this diagnosis, the practical takeaways are:
Every case is unique, and the final treatment plan should be tailored to the individual patient's cancer biology, gestational age, and personal values. But the overarching principle from this expert panel is clear: pregnancy should not be a barrier to receiving optimal breast cancer care.
Yes. Experts now recommend treating breast cancer during pregnancy rather than delaying treatment or terminating the pregnancy. Surgery, sentinel lymph node biopsy, and certain chemotherapy regimens can be safely given in the second and third trimesters. Chemotherapy is avoided in the first trimester. Your care team will tailor treatment to your cancer and gestational age.
Chemotherapy given in the second and third trimester does not raise the risk of major birth defects above the general population rate of about 3%. In the first trimester, however, the risk is about 14%. Doctors stop chemotherapy around weeks 35 to 37 so your blood counts recover before delivery. The doctor will discuss risks and benefits with you.
Delaying or postponing chemotherapy may increase the risk of breast cancer relapse. Data from nonpregnant young women show that waiting can be harmful. Treating during pregnancy, when possible, gives outcomes similar to those of nonpregnant patients. Your oncologist will plan the safest timing for you and your baby.
Yes. Mastectomy or breast-conserving surgery is offered on the same indications as for nonpregnant women. Pregnancy alone is not a reason to choose mastectomy. Sentinel lymph node biopsy with a radioactive tracer can be performed safely and accurately during pregnancy. Blue dye alone is not recommended due to allergy risk.
Radiation therapy is usually postponed until after delivery. It may be considered in the first or early second trimester in rare cases if the benefit is believed to outweigh the risk. The fetal dose can be reduced by shielding, but long-term effects are not well studied. This decision is made individually by your care team.
When standard treatment is given, survival is similar to that of nonpregnant young women with breast cancer. The largest cohort study, with 313 patients, found no difference in survival after accounting for cancer stage and treatment. A diagnosis during pregnancy is not an independent poor prognostic factor if you receive appropriate, timely treatment.
Breast ultrasound and mammography are safe during pregnancy. The fetal radiation dose from a mammogram is extremely low, less than 0.03 μGy, far below the 100 mGy threshold for harm. A core biopsy is the gold standard. Do not delay evaluation of a breast lump; all palpable masses require imaging and biopsy without delay.
Original article title: Breast Cancer Diagnosed During Pregnancy Adapting Recent Advances in Breast Cancer Care for Pregnant Patients
Authors: Sibylle Loibl, MD, PhD; André Schmidt, PhD; Oreste Gentilini, MD; Bella Kaufman, MD; Christine Kuhl, MD; Carsten Denkert, MD; Gunter von Minckwitz, MD; Anastasia Parokonnaya, MD; Hanne Stensheim, MD, PhD; Christoph Thomssen, MD; Kristel Van Calsteren, MD, PhD; Philip Poortmans, MD, PhD; Paul Berveiller, MD; Udo R. Markert, MD; Frederic Amant, MD, PhD
Publication: JAMA Oncology, November 2015, Volume 1, Number 8, pages 1145–1153. doi:10.1001/jamaoncol.2015.2413. Published online August 6, 2015; corrected November 12, 2015.
Note: This patient-friendly article is based on peer-reviewed research published in a leading medical journal. It is intended for educational purposes and does not replace individualized medical advice from your oncology and obstetrics care teams.
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