Breast Cancer During Pregnancy: A Patient's Guide to the 2023 ESMO Expert Consensus

Table of Contents

• Key Points
• Why This Expert Consensus Was Needed
• How the Experts Reached Consensus
• Pregnancy vs. Postpartum Breast Cancer: Two Distinct Diseases
• Why Breast Cancer During Pregnancy Is Becoming More Common
• Genomic Testing: Can It Help Guide Treatment Decisions?
• Diagnostic Imaging: What Is Safe and Accurate During Pregnancy?
• Systemic Staging: Checking Whether Cancer Has Spread
• Tumor Biology: Are Pregnancy Cancers Different at a Cellular Level?
• Prognosis: Does Pregnancy Affect Survival?
• Chemotherapy During Pregnancy: What the Experts Say
• What This Means for Patients
• Limitations of This Consensus
• Recommendations for Patients and Families
• Frequently Asked Questions
• Source Information

Key Points

• Pregnancy-related and postpartum breast cancer are biologically distinct and should be studied separately.
• When adequately treated, breast cancer during pregnancy has survival similar to non-pregnant young patients with the same stage and subtype.
• Chemotherapy is safe after the first trimester but avoided before 14 weeks and usually after 35 weeks.
• Breast ultrasound is first-line; MRI with gadolinium is avoided, but diffusion-weighted MRI is a safer alternative.
• Delayed childbearing is the most likely reason for the rising number of pregnancy-related breast cancer diagnoses.

Why This Expert Consensus Was Needed

Breast cancer during pregnancy (technically called pregnancy-related breast cancer, or PrBC) is a relatively rare diagnosis — but its incidence is rising. While breast cancer in young women has been increasing across many populations, managing the disease during pregnancy presents unique challenges that don't apply to other patients.

The fundamental difficulty is this: no randomized controlled trials (the gold standard of medical research) can be conducted in pregnant patients. That means doctors have very little high-quality evidence to guide treatment decisions.

Even worse, advances in breast cancer treatment developed for non-pregnant patients cannot always be simply transferred to pregnant patients. Why? Because in PrBC, doctors must simultaneously consider both the interests of the mother and the safety of the unborn baby. Every treatment decision becomes a delicate balancing act.

In 2022, the European Society for Medical Oncology (ESMO) recognized that evidence remained limited and sometimes conflicting in several specific areas where the optimal approach was still controversial. The organization convened a virtual consensus-building process to gather insights from a multidisciplinary group of experts and develop statements on these debated topics — topics that could not be adequately addressed in the existing evidence-based ESMO Clinical Practice Guideline.

The overall lack of high-level evidence around this topic underscores why these statements reflect expert opinion. And precisely because the evidence is limited, the experts emphasized that it is even more important to include patients and their partners in all clinical decision-making. Their values, concerns, and preferences matter enormously when evidence is incomplete.

How the Experts Reached Consensus

The consensus-building process was carefully planned and executed according to ESMO's standard operating procedures. A multidisciplinary panel of 24 leading experts from 13 countries participated in the virtual meeting, chaired by Dr. Sibylle Loibl (Germany) and Dr. Frédéric Amant (Belgium/Netherlands).

All experts were divided into three working groups, each covering a specific subject area with two appointed chairs:

1. Working Group 1 (WP1): PrBC incidence, epidemiology, biology and pathology, diagnostic work-up, staging and risk assessment, and prognosis — chaired by Dr. Vincent Vandecaveye and Dr. Fedro Peccatori.
2. Working Group 2 (WP2): Clinical pharmacology of systemic agents during pregnancy, management of localized disease and (neo)adjuvant therapies, and management of systemic disease — chaired by Dr. Giuseppe Curigliano and Dr. Peter Schmid.
3. Working Group 3 (WP3): Obstetric care and fetal/newborn follow-up and outcomes, metastases to the fetus, management of pregnancy during anticancer therapy, lactation, and psychological support — chaired by Dr. Elyce Cardonick and Dr. Mathilde van Gerwen.

No systematic literature search was undertaken for this process. Instead, each statement compiled by the working groups was accompanied by a level of evidence and strength of recommendation based on the 'Infectious Diseases Society of America-United States Public Health Service Grading System,' along with the percentage of expert consensus calculated from votes of agreement or disagreement (abstentions were counted as null votes).

This means that each statement tells you not only what the experts concluded, but also how confident they are in that conclusion and how united they were in reaching it. The final manuscript was reviewed and approved by all panel members.

Pregnancy vs. Postpartum Breast Cancer: Two Distinct Diseases

Question 1: Is breast cancer diagnosed during pregnancy distinct from that diagnosed during the postpartum period?

Statement 1 (Level of evidence: III): Breast cancers diagnosed in the postpartum period are biologically distinct from those diagnosed during pregnancy. Given the biological differences and unique challenges associated with managing PrBC, future studies should aim to study each group independently.

Consensus: 24 agree, 0 disagree — 100% consensus

What does this mean for patients? Pregnancy-related breast cancer is defined as breast cancer diagnosed during pregnancy or within one year after delivery. However, childbirth at any age confers a temporarily increased risk of breast cancer soon after delivery, with a lower risk within the first few years postpartum.

The experts explained that epidemiological, clinical, and biological data now clearly show that PrBC is a separate entity from tumors diagnosed in the postpartum period (known as postpartum breast cancer, or PPBC). The reason lies in the biology of the breast itself. In fact, PPBC diagnosed up to 10 years after pregnancy has been associated with a worse prognosis.

The mammary gland is a highly dynamic tissue that reaches its maximum functional differentiation during lactation, when it produces milk to provide nutrition and immunological protection to the baby. When lactation ends and weaning takes place, the excess tissue developed during pregnancy and lactation must regress to its pre-pregnant state in a process called postpartum involution.

During this key developmental stage, the breast is characterized by massive cell death (apoptosis), wound-healing processes, and suppression of T-cells (a type of immune cell). This peculiar environment appears to allow — and even promote — disease progression in PPBC. The experts noted that cancer care for women diagnosed during pregnancy needs to be individualized according to disease stage and tumor biology, just as with any other breast tumor, but it must also account for gestational age and fetal safety. In contrast, treatment decisions for PPBC do not need to consider these fetal concerns — although the postpartum setting is a poor prognostic factor, and standard treatment for high-risk disease is mandatory.

The practical takeaway: PrBC and PPBC must be considered distinct diseases. The experts recommended that parity (number of pregnancies) and the age at first and last delivery should be accurately recorded in the medical history of any breast cancer patient to assess prognosis. Further research is needed to better characterize both diseases.

Why Breast Cancer During Pregnancy Is Becoming More Common

Question 2: What is the likely reason for the recent increasing trend in diagnosed breast cancer during pregnancy?

Statement 2 (Level of evidence: III): The rising trend of delaying childbearing to later in life appears to be the most likely reason for the increasing diagnosis of PrBC.

Consensus: 24 agree, 0 disagree — 100% consensus

Breast cancer incidence in premenopausal women is increasing over time across many populations, and most — though not all — studies have found an increasing incidence of PrBC. But what's driving this trend?

The answer is surprisingly straightforward. Breast cancer risk increases with age. If women postpone childbearing into ages where breast cancer is more common, then the incidence of PrBC will increase — regardless of what the underlying incidence trend in breast cancer is doing. Studies have found that the increasing incidence of PrBC appears to be less strong when age is adjusted for, supporting this explanation.

Other potential factors that could explain the increasing incidence are "confounding factors" — characteristics associated with both pregnancy and breast cancer rates. Incidence could rise if there are growing groups in the population with both higher childbearing rates and higher breast cancer rates. But the experts' clear consensus is that delayed childbearing is the dominant explanation.

Genomic Testing: Can It Help Guide Treatment Decisions?

Question 3: Could genomic assays be used to refine the risk of recurrence and to inform the type of adjuvant (post-surgery) systemic therapy in pregnant patients with estrogen receptor-positive (ER+) disease?

Statement 3 (Level of evidence: V): Debate exists on the performance of genomic assays in stratifying the risk of premenopausal women. These assays can be considered to assist decision-making in pregnant women with node-negative (pN0) ER+ breast cancer, but patients should be informed about potential limitations in the risk assessment and the limited level of evidence, especially in the pregnant population.

Consensus: 21 agree, 1 disagree, 2 abstain — 95.45% consensus

Genomic assays (also called genomic signatures) are tests that analyze the genetic activity of a tumor to predict how likely it is to recur and whether chemotherapy will add benefit. But how well do they work in pregnant patients?

The honest answer: no studies have specifically evaluated the prognostic performance of commercially available genomic signatures in patients diagnosed with PrBC. Only one study has looked at the gene expression of a specific gene set called GENE70, and no difference was found between pregnant and non-pregnant groups.

Even outside pregnancy, there is debate about how well genomic signatures perform in young patients with breast cancer and whether they can reliably identify patients who can safely skip chemotherapy. However, critical analyses point to their clinical utility.

Here's the biological backdrop: unlike in postmenopausal patients, the majority of ER+ tumors diagnosed in young patients are of the highly proliferative luminal-B genotype — a more aggressive subtype that benefits more from chemotherapy. Nevertheless, a fraction of breast cancers occurring in young women (estimated around 15%–20%) are of the luminal-A genotype, in which endocrine therapy alone would suffice.

The experts concluded that even though data are lacking in the specific scenario of pregnant patients with early-stage ER+ breast cancer, genomic testing could be considered in node-negative (pN0) patients to confirm a low-risk situation. If confirmed low-risk, endocrine therapy alone might be appropriate — but it must be deferred until the postpartum period, because endocrine therapies are not safe during pregnancy.

Diagnostic Imaging: What Is Safe and Accurate During Pregnancy?

Question 4: What diagnostic imaging modalities should be used for diagnosis and locoregional staging (determining the extent of cancer within the breast and nearby lymph nodes) in PrBC?

Statement 4 (Level of evidence: III): Breast ultrasound is the first-line imaging modality for primary tumor assessment and staging of regional and supraclavicular lymph nodes and is complemented by mammography — or, in selected cases, magnetic resonance imaging (MRI) with diffusion-weighted sequences to aid in delineating tumor extent and multifocality.

Consensus: 23 agree, 0 disagree, 1 abstain — 100% consensus

Breast ultrasound is the go-to first-line imaging tool for locoregional staging. It allows immediate differentiation between obviously benign lesions such as cysts and galactocoeles (milk-filled cysts) and solid breast lesions that warrant a core biopsy. In a non-pregnant population, ultrasound has an overall sensitivity (ability to correctly identify cancer) of 80.1% and a specificity (ability to correctly identify no cancer) of 88.4%.

An additional mammography is indicated in a single mediolateral oblique view (a specific angled x-ray view) to look for microcalcifications or tissue distortions when the initial assessment suggests malignancy.

Ultrasound is also the primary imaging modality for assessing axillary and periclavicular (around the collarbone) lymph nodes, with reported sensitivity between 26.4% and 92% and specificity between 55.6% and 98.1% in a non-pregnant population. In the same population, ultrasound-guided core biopsy or fine-needle aspiration cytology (FNAC) of lymph nodes can further improve pre-operative determination of nodal status. The sensitivity of ultrasound-guided FNAC for lymph nodes ranges from 36% to 86.4%, with specificity from 95.7% to 100%. Because of the high positive predictive value of ultrasound-guided FNAC (meaning a positive result is highly reliable), this approach is very valuable for planning axillary lymph node dissection.

It's important to note that changes in breast tissue during pregnancy will impact the accuracy of these imaging modalities.

What about MRI? The experts strongly advised that dynamic contrast-enhanced (DCE) breast MRI should be avoided, because exposing the fetus to gadolinium contrast increases the risk of rheumatological, inflammatory, or dermal conditions in the child, as well as stillbirth or neonatal death.

However, there's a safer alternative: diffusion-weighted imaging (DWI), a non-contrast MRI technique. Non-contrast breast MRI has sensitivities between 72.4% and 97% and specificities between 54.4% and 91.7% for regional nodal staging, and sensitivities between 75.7% and 78.9% to assess multifocality or contralateral breast involvement. Although non-contrast breast MRI can be of complementary value to ultrasound for locoregional staging, it is rarely indicated in this setting.

The experts also noted that the need for shielding during diagnostic and staging procedures is best discussed with the radiologist. Modern equipment more precisely directs the beam without fetal harm. In cases where the primary beam is less precise, fetal shielding is advised.

Systemic Staging: Checking Whether Cancer Has Spread

Question 5: What is the optimal imaging strategy for systemic staging (checking whether cancer has spread to other parts of the body) in PrBC?

Statement 5 (Level of evidence: III): Locoregional tumor stage (the extent of cancer in the breast and nearby lymph nodes) determines the staging strategy during pregnancy. Chest X-ray and abdominal ultrasound are easily accessible for initial screening of metastases. If inconclusive, or if there is a high risk of metastases, additional non-contrast MRI with DWI of the full spine and pelvic bone and liver, combined with chest computed tomography (CT), is suggested. When available on-site, whole-body MRI with diffusion-weighted sequence (WB-DWI/MRI) is recommended as a single-step staging modality.

Consensus: 22 agree, 0 disagree, 2 abstain — 100% consensus

The initial locoregional tumor stage and the histopathological diagnosis will generally determine how much imaging is needed. Most patients with early breast cancer are unlikely to benefit from extensive staging.

However, in the presence of risk factors, imaging for distant staging should be considered. Risk factors include:

• Clinically positive axillary lymph nodes
• Large tumors (e.g., diameter larger than 5 cm)
• Aggressive tumor biology (e.g., triple-negative tumors, HER2-positive tumors, luminal breast cancer with high Ki67 — a marker of cell proliferation)
• Clinical or laboratory signs suggesting the presence of metastases

Current international guidelines show no consensus on how and when to screen for metastases over the most frequently affected sites, including the skeleton, liver, and lungs. Chest X-ray and liver ultrasound provide easily accessible and rapid screening, but their use should be carefully weighed against the risk of metastatic disease because they have relatively low sensitivity for detecting lung and liver metastases and cannot detect skeletal metastases at all.

In cases of high clinical suspicion of metastatic disease, staging should be expanded with non-contrast MRI with DWI of the spine, pelvis, and liver, combined with low-dose chest CT. Chest CT offers superior sensitivity with minimal radiation exposure to the fetus. Skeletal MRI with DWI has shown high pooled sensitivity and specificity for detecting skeletal metastases — superior to bone scintigraphy in an updated meta-analysis. Liver MRI with DWI provides excellent diagnostic performance for detecting liver metastases, equivalent to contrast-enhanced MRI.

The experts highlighted whole-body MRI with diffusion-weighted imaging (WB-DWI/MRI) as an emerging and valuable tool. It has been shown to allow accurate identification of the primary tumor and more accurate staging of nodal and distant metastases in a single step compared to conventional staging — particularly in pregnant patients with breast cancer. WB-DWI/MRI has demonstrated high accuracy for detecting bone, liver, and peritoneal metastases, and it can detect additional lymph node metastases regardless of nodal morphology. It should only be complemented by unenhanced chest CT when lung nodules are equivocal on MRI. When available on-site, WB-DWI/MRI is recommended as a single-step staging modality.

What about nuclear imaging? Nuclear imaging tracers induce relatively low fetal radiation exposure. However, the standard use of hybrid imaging with CT increases the final cumulative dose, ranging between 10 and 50 mGy. Therefore, low-dose positron emission tomography (PET)/CT and bone scintigraphy are only recommended as second-line imaging modalities, to be selectively carried out in case of unresolved distant findings when the benefit for the mother clearly outweighs the risk to the fetus and/or when MRI is not available. The staging strategy is best discussed with the radiologist and physicist to minimize fetal exposure, using a cumulative exposure of 100 mGy as the maximum acceptable threshold.

Tumor Biology: Are Pregnancy Cancers Different at a Cellular Level?

Question 6: Does PrBC have different biological features compared to breast cancer in patients of the same age and stage?

Statement 6 (Level of evidence: III): Limited biological differences exist in tumors when diagnosed during pregnancy. Yet, to date, this does not appear to have an important impact on patient management.

Consensus: 21 agree, 1 disagree, 2 abstain — 95.45% consensus

Several studies have examined differences in classic clinicopathological features between pregnant and young non-pregnant breast cancer patients. The experts found that histological grade and subtype were consistently comparable between both groups.

However, a few studies have pointed out a tendency toward a higher proportion of ER-negative (ER−) tumors in pregnant patients, although the differences hardly reach statistical significance in any of the individual studies. The largest study included 311 pregnant patients and 865 non-pregnant patients, and found that the proportion of ER− tumors was almost doubled in pregnant compared to non-pregnant patients: 53.4% versus 25.5%.

At the molecular level, tumors diagnosed during pregnancy were shown to have high levels of RANK ligand (RANKL) — a protein involved in bone metabolism and immune regulation. This finding underscores the potential impact of pregnancy on the breast microenvironment, which subsequently alters tumor biology.

At the genomic level, the pattern of common somatic mutations (such as TP53, PIK3CA, etc.) appears to be rather comparable between pregnant and age-matched non-pregnant breast cancer patients. However, whole-genome sequencing analysis showed:

• A higher frequency of non-silent mutations (mutations that actually change the protein product)
• A higher frequency of mutations in the mucin gene family
• An enrichment in the mismatch repair deficiency mutational signature

The potential clinical implications of these findings are not yet clear, although they could suggest that some pre-existing subclones (small populations of genetically distinct cancer cells) could have a growth advantage during pregnancy. For now, the experts concluded that these biological differences do not significantly change how patients should be managed.

Prognosis: Does Pregnancy Affect Survival?

Question 7: Does PrBC have a worse prognosis compared to breast cancer in young patients of the same stage and disease subtype?

Statement 7 (Level of evidence: II): The prognosis of breast cancer diagnosed during pregnancy is similar to that in young breast cancer patients with the same stage and disease subtype, provided it is adequately managed.

In the past, several studies appeared to show that PrBC carries a worse prognosis. For example, in a nationwide registry-based study of 234 patients diagnosed with PrBC from 1970 to 2018, the hazard ratio (HR) of death was 1.80 (95% confidence interval 1.43–2.28) — meaning an 80% higher risk of death. A recent large meta-analysis of 76 studies reported an HR of death of 1.46 (95% CI 1.12–1.90) for patients with PrBC.

But here's the critical insight: the experts explained that a key observation from these studies is that patients were not necessarily adequately treated during pregnancy, and some analyses even included breast cancers diagnosed within one year of delivery (which we now know behaves differently — see the pregnancy vs. postpartum section above).

When patients receive similar, standard treatment, the picture changes dramatically:

• The largest case-control study to date, including 311 patients diagnosed with PrBC and 865 non-pregnant controls, found an HR for overall survival of 1.06 (95% CI 0.66–1.68) — essentially no difference — with patients receiving similar treatments regardless of pregnancy status.
• A series of 58 triple-negative PrBCs, where a propensity score-matched analysis was carried out with 92 non-pregnant patients, found no differences in survival.
• A recent study of more than 600 patients with PrBC who were treated with chemotherapy during pregnancy supports these earlier findings.

Thus, the experts concluded that — if adequately treated — pregnant breast cancer patients would have highly comparable prognoses to patients of the same age and stage who are not pregnant.

Importantly, this is not the case for postpartum breast cancer (PPBC). The involuting breast (returning to its non-pregnant state after weaning) with its peculiar immunological environment is responsible for a higher risk of progression in PPBC. This underscores again why PrBC and PPBC must be treated as distinct entities with different considerations.

Chemotherapy During Pregnancy: What the Experts Say

Question 8 (partial): The article continues into the second working group's territory, addressing systemic therapy management during pregnancy.

Statement 9 (Level of evidence: V): Chemotherapy is contraindicated in the first trimester of gestation to avoid interference with organogenesis (the formation of organs). The fetal benefit of delaying treatment until the second trimester should be balanced against maternal risk. Although fetal growth impairment is associated with earlier start of chemotherapy, children reach their developmental milestones. Therefore, chemotherapy can be administered during the second and third trimesters.

Chemotherapy is strictly avoided in the first trimester of pregnancy because early exposure has been associated with up to a 20% risk of major malformations. The decision about whether to delay treatment until the second trimester must carefully balance the fetal benefit against the maternal risk — a discussion that should involve the patient, her oncology team, and her obstetrics team.

The experts clarified that chemotherapy is associated with an increased risk of congenital malformations only in the first 12 weeks of pregnancy. After 12–14 weeks of gestation, administration of a number of chemotherapy drugs is safe and feasible. Standard (neo)adjuvant anthracycline-taxane-based regimens (a common chemotherapy backbone for breast cancer) can be administered as in the non-pregnancy setting.

After 35 weeks of gestation, chemotherapy on a 3-weekly schedule is usually discouraged. This is likely to minimize the risk of chemotherapy-related complications (such as low white blood cell counts) coinciding with delivery, which could increase infection risk for the mother and baby.

It's reassuring to note that although fetal growth impairment is associated with an earlier start of chemotherapy, studies show that children reach their developmental milestones, suggesting that the long-term developmental outlook is favorable.

What This Means for Patients

These consensus statements carry powerful messages for patients facing breast cancer during pregnancy:

• Your prognosis is not necessarily worse. When treated appropriately, pregnant patients with breast cancer have survival outcomes comparable to non-pregnant patients of the same age, stage, and tumor subtype. However, this depends on you and your care team proceeding with standard, effective treatment — not delaying or reducing treatment out of caution.
• Your cancer is not the same as postpartum breast cancer. The biological differences matter for treatment decisions, and researchers will study these groups separately in the future.
• Delayed childbearing explains the rising numbers. If you're diagnosed during pregnancy, you're part of a growing group — and that means more research and more awareness among doctors than ever before.
• Imaging is available and safe. Ultrasound is the first step, and newer whole-body MRI techniques offer comprehensive staging in a single scan without exposing your baby to gadolinium contrast or significant radiation. If you're told an MRI with contrast is needed, ask about diffusion-weighted imaging instead. Talk to the radiologist about shielding and cumulative radiation doses.
• Chemotherapy is possible. Chemotherapy can be safely given in the second and third trimesters, after organogenesis is complete (roughly after weeks 12–14). It's only the first trimester — when organs are forming — that chemotherapy is strictly avoided. The timing of chemotherapy near delivery (after 35 weeks) also needs careful planning.
• Genomic testing might help, but with caveats. For node-negative ER+ disease, genomic assays could help confirm a low-risk situation where endocrine therapy alone might suffice — but any such treatment would be deferred until after delivery, and there are known limitations to these tests in younger patients.

Limitations of This Consensus

It's important for patients to understand the limitations of this guidance:

• No randomized controlled trials can be conducted in pregnant patients with breast cancer, so the highest level of evidence (randomized trials) will never exist in this field. This is an ethical necessity, not a research gap.
• No systematic literature search was undertaken as part of this consensus process. Instead, the statements are based on the experts' collective review and interpretation of the available evidence.
• The level of evidence is mostly III to V (meaning evidence from non-randomized studies, case series, or expert opinion), not level I or II. Only the prognosis statement reached level II.
• No studies have specifically evaluated genomic signatures in pregnant patients, so genomic testing recommendations rely on extrapolation from non-pregnant younger patients.
• Consensus percentages ranged from 95.45% to 100%. While this represents very strong agreement, a small number of experts either disagreed or abstained on certain statements, reflecting the genuine controversy and uncertainty that remains in some areas.
• The article text available for this patient guide includes the full Working Group 1 discussion and the start of Working Group 2's chemotherapy guidance; additional topics such as obstetric care, fetal/newborn outcomes, lactation, and psychological support (Working Group 3) were part of the consensus process and are covered elsewhere in the original document.

Recommendations for Patients and Families

If you or a loved one has been diagnosed with breast cancer during pregnancy, here are practical steps to consider, based on the experts' statements:

1. Seek a multidisciplinary care team. Your care should be coordinated among a breast cancer oncologist, a maternal-fetal medicine specialist (high-risk obstetrician), a radiologist experienced in imaging pregnant patients, a pathologist, and — if chemotherapy is planned — a pharmacist familiar with medication safety in pregnancy. In many countries, specialized breast cancer centers have dedicated programs for pregnancy-related cancer.
2. Be an active participant in decision-making. The experts explicitly emphasized that because high-level evidence is lacking, patient and partner preferences are essential in choosing among reasonable options. Ask questions, express your priorities, and make sure your team understands your goals for both your health and your baby's health.
3. Ask about imaging safety. Request breast ultrasound as the first step. If MRI is recommended, ask specifically whether it will use contrast (gadolinium) — which should be avoided — or diffusion-weighted imaging, which is safe. For staging, ask about whole-body DWI/MRI as a single-step alternative to multiple scans, and discuss cumulative radiation doses with a physicist.
4. Discuss chemotherapy timing. If chemotherapy is recommended, the plan will likely aim to start after the first trimester (12–14 weeks) and will be timed to avoid the period right before delivery (after 35 weeks). Standard regimens such as anthracycline-taxane combinations can be used.
5. Consider genomic testing

   Frequently Asked Questions

   Is breast cancer during pregnancy different from breast cancer after giving birth?

   Experts consider them distinct diseases. Pregnancy-related breast cancer is diagnosed during pregnancy or within one year after delivery, while postpartum breast cancer has different biology and a worse prognosis. Treatment for pregnancy-related cancer must balance maternal care with fetal safety, whereas postpartum treatment does not have that added concern.

   What imaging tests are safe and accurate during pregnancy for breast cancer?

   Breast ultrasound is the first-line test. A single-view mammography can complement it. MRI with gadolinium contrast should be avoided due to fetal risks, but non-contrast diffusion-weighted MRI is safer. For staging, chest X-ray and abdominal ultrasound are initial options; whole-body diffusion-weighted MRI is recommended if available.

   Does breast cancer during pregnancy lead to worse survival?

   When treated adequately, the prognosis is similar to non-pregnant young patients with the same stage and subtype. A study of 311 pregnant and 865 non-pregnant patients found no significant difference in overall survival. Earlier studies suggesting worse outcomes often included postpartum cancers or patients who did not receive standard treatment.

   Should I have genomic testing on my breast cancer tumor during pregnancy?

   Genomic assays can be considered for node-negative estrogen receptor-positive cancer to help assess recurrence risk and whether chemotherapy might be avoided. However, no studies have tested these assays specifically in pregnant patients, and there are limitations in younger patients. If low-risk, endocrine therapy would be delayed until after delivery.

   How reliable is this expert guidance on breast cancer during pregnancy?

   Because randomized trials cannot be conducted in pregnant patients, the guidance comes from 24 experts reviewing available evidence and voting. Evidence levels are mostly III–V, meaning not from randomized trials. Consensus ranged from 95.45% to 100%. Patients and partners should be central in all treatment decisions.