Pregnancy During Cancer Treatment

About 1 in 1,000 pregnant women receives a cancer diagnosis, according to the National Cancer Institute. That is uncommon. It is not rare enough to improvise.

The first fear is usually that treatment must wait nine months, or that the pregnancy must end. Neither is usually true. Most of the work is sorting three piles. What happens now. What shifts by a few weeks. What waits until after birth.

This question comes up early, so here is the evidence. The NCI PDQ summary on breast cancer during pregnancy is direct. Termination of pregnancy has not shown any beneficial effect on breast cancer outcome. It is not usually considered a treatment option.

That is a statement about survival data. It is not a statement about your choices. It simply takes one argument off the table.

Cancer care in pregnancy runs on two calendars at once. The usual team is:

• A medical oncologist for the drug plan
• A surgeon, if surgery is part of it
• A maternal-fetal medicine specialist, meaning an obstetrician trained in high-risk pregnancy
• A neonatologist, if early delivery looks likely

Ask who is chairing. One named person should hold both calendars. NCI also describes two groups that field questions like yours. The Cancer and Pregnancy Registry started in 1997 and holds data on about 450 women. INCIP is the International Network on Cancer, Infertility and Pregnancy.

Ultrasound comes first and uses no ionizing radiation. MRI is used for staging when needed. The caution with MRI is the contrast dye. NCI notes that gadolinium crosses the placenta and has caused fetal abnormalities in rats. Many scans in pregnancy are done without it.

Fetal dose from plain X-rays is small. NCI's breast cancer summary lists a chest X-ray with abdominal shielding at 0.00008 Gy. A bone scan comes in at 0.001 Gy. Gy stands for gray, the unit of absorbed radiation dose. The number that matters sits far above those. First-trimester exposure above 0.1 Gy may cause birth defects and intellectual disability.

Mammography can be done with shielding. Know its weak spot in pregnancy. NCI reports that at least 25% of mammograms in pregnancy may be negative when cancer is in fact present, because pregnant breast tissue is dense. A clean mammogram does not settle the question when there is a lump you can feel.

Surgery is the primary treatment for pregnant women with breast cancer, per the NCI summary. Biopsies can be done under local anesthesia.

Sentinel lymph node biopsy is the debated part. This maps the first lymph node the breast drains into. NCI describes limited safety data from a series of 25 cases across all trimesters. Technetium Tc 99m or methylene blue was used, and 24 of the 25 infants were healthy. That is thin evidence. It should be described to you as thin.

In cervical cancer, the NCI pregnancy summary sets a clearer line. Surgical lymph node assessment can be done up to about 20 weeks of pregnancy.

The rule holds across cancer types. NCI states that chemotherapy is generally safe in the second and third trimesters when treatment cannot wait until after delivery. It is avoided in the first trimester, while organs are forming.

For breast cancer, anthracycline-based regimens carry the most evidence. NCI names doxorubicin plus cyclophosphamide, and FAC, which is fluorouracil, doxorubicin, and cyclophosphamide. In one reported group of 57 pregnant patients given FAC, there were no stillbirths, miscarriages, or perinatal deaths. Data on taxanes is much thinner.

The cervical summary agrees on the principle. Most chemotherapy drugs can be given safely from the second trimester onward. Mild fetal growth restriction is the most common side effect. Long-term outcome data is limited, and NCI says so rather than glossing over it.

Ask where your last cycle falls relative to your due date. That gap is planned, not accidental.

Some drugs cannot be given while you are pregnant.

• Trastuzumab, the HER2-targeted antibody, is contraindicated. NCI reports that 73.3% of pregnancies exposed in the second or third trimester developed oligohydramnios or anhydramnios. Those mean too little amniotic fluid, or none.
• Tamoxifen has been linked to vaginal bleeding, miscarriage, birth defects, and fetal death.
• Endocrine therapy as a whole is generally avoided until after delivery.

Immunotherapy sits in a gray zone. NCI describes nine patients who became pregnant during checkpoint inhibitor trials. Seven continued the pregnancy, and all of those delivered healthy infants. Nivolumab was detected in cord blood, so the drug does reach the fetus. Nine cases is not a safety record.

Chest radiation can often be pushed to after delivery. NCI says first-trimester radiation should be avoided, and that radiation after birth is acceptable for breast cancer.

Pelvic radiation is a different matter. The cervical cancer summary is blunt. Radiation typically causes spontaneous abortion 3 to 5 weeks after treatment starts. It also leaves the ovaries nonfunctional unless they are surgically moved out of the treatment field.

Cervical cancer shows the logic best. NCI puts it at about 1 to 12 cases per 10,000 pregnancies. The plan turns on stage:

• Stage IA: conization or radical trachelectomy, ideally in the second trimester before fetal viability
• Stages IA2 and IB with clear lymph nodes: therapy may wait for fetal viability
• Stages II, III, and IV: delaying to viability is generally not appropriate
• Small cell or neuroendocrine subtypes: treat now, whatever the stage

Breast cancer during pregnancy affects about 1 in 3,000 pregnant women. NCI gives the usual age range as 32 to 38 years.

If you are on chemotherapy, do not breastfeed. NCI states this plainly. Cyclophosphamide and methotrexate reach high levels in breast milk.

Ask about each drug by name, not about chemotherapy in general. Ask when nursing becomes safe again, and whether pumping and discarding milk is worth doing in the meantime.

Go to an emergency department, or your labor and delivery unit, right now for any of these:

• Fever of 100.4 °F (38 °C) or higher, the threshold CDC gives during cancer treatment. A fever on chemotherapy is an emergency, not a message left with the clinic — your white cell count may be too low to fight the infection off.
• Heavy vaginal bleeding, or a gush of fluid
• Regular contractions before 37 weeks
• A clear drop in how much the baby moves, or no movement at all
• Severe headache with blurred vision, or sudden swelling of the face and hands — these can signal pre-eclampsia
• Severe or constant abdominal pain
• Trouble breathing, chest pain, or a swollen painful calf

Call the same day for lighter spotting, chills, sore throat, or burning when you urinate while on chemotherapy.

Make sure both teams hold each other's phone numbers. If you go to labor and delivery, tell them the chemotherapy drug by name and the date of your last dose.

Cancer and Fertility covers planning before treatment begins. Cancer as a Young Adult deals with the age group where this comes up most. Sexual Health and Cancer picks up afterward.

• NCI PDQ — Breast Cancer Treatment During Pregnancy (Health Professional Version)
• NCI PDQ — Cervical Cancer Treatment During Pregnancy (Health Professional Version)
• National Cancer Institute — Treating Cancer during Pregnancy: New Drugs, Old Questions
• National Cancer Institute — Infection and Neutropenia during Cancer Treatment