Cancer diagnosed during pregnancy: tests, treatment options and outlook

Symptoms of cancer can be mistaken for the normal changes of pregnancy, and the worry about scans or procedures can make doctors hesitant to investigate. A narrative review describes diagnosis as often delayed for exactly those reasons, and notes that some tests become less accurate in pregnancy. For example, breast tissue becomes denser during pregnancy, which can make changes harder to detect.

Cancer Research UK advises seeing your GP if you notice a lump, nipple discharge or skin changes on the breast. The RCOG adds that the natural changes in the breast during pregnancy and breastfeeding should not stop a lump being checked, and that most breast lumps are not cancer. A new lump or any other symptom that is unexplained or does not settle deserves assessment by a GP or midwife rather than reassurance alone.

Ultrasound and MRI without contrast are the preferred imaging methods because they do not use ionising radiation. Cancer Research UK explains that for suspected breast cancer the first test is an ultrasound, usually with an ultrasound-guided biopsy, and that a mammogram can be done with the baby shielded. CT scans and bone scans are not usually recommended in pregnancy because of the radiation dose.

The review adds that some imaging techniques should be avoided or used only if necessary: CT of the abdomen and pelvis and some nuclear medicine techniques deliver higher doses, gadolinium contrast is not recommended unless it will improve outcomes, and radioactive iodine should not be used. Common tumour marker blood tests such as CA 125 and AFP rise in pregnancy and are not reliable. Pathologists should be told the woman is pregnant, because pregnancy changes in the breast and cervix can resemble cancer.

Both the RCOG and Cancer Research UK state that breast cancer surgery can be carried out at any time in pregnancy, either removing the lump or the whole breast, with some armpit lymph nodes sometimes removed. The review concludes more broadly that cancer surgery under anaesthesia can be done at any time and should not be delayed if indicated, although the chance of miscarriage is slightly raised in the first trimester and low birth weight and premature birth are somewhat more likely.

Radiotherapy is normally delayed until after birth because of the dose to the baby. The review says it may be considered in emergencies such as spinal cord compression, or for areas far from the baby such as the head and neck, with careful shielding and planning. Radiotherapy to the abdomen or pelvis cannot be given without harming the baby, which is one of the situations in which ending the pregnancy may be discussed.

The RCOG states that chemotherapy is not given during the first 13 weeks because it could cause abnormalities, while Cancer Research UK says doctors delay it until you are at least 14 weeks pregnant. A systematic review of neonatal outcomes concluded that risk to the baby is low when chemotherapy begins in the second or third trimester, and that long-term outcomes of children exposed in the womb appear reassuring. Chemotherapy can affect the baby's growth, so extra scans are offered. It usually stops 2 to 3 weeks before a planned birth, to reduce the risk of infection and bleeding during delivery.

The review lists other drug groups that are avoided or delayed. Tamoxifen and other hormone treatments are contraindicated, trastuzumab is linked with low amniotic fluid, imatinib has been associated with miscarriage and malformations, and immune checkpoint inhibitors are not recommended because of a lack of human data. Anti-sickness medicines and steroids used for side effects are safe in pregnancy, according to the RCOG.

The RCOG says most women with breast cancer choose to continue the pregnancy during treatment, and that outcomes are generally the same whether or not the pregnancy continues. If the cancer is advanced or found in the first three months, the team discusses the option of ending the pregnancy, or of early delivery if the baby is viable, so that treatment can start sooner.

These are deeply personal decisions, and the team should give time, written information and access to psychological support. Specialist charities and the breast care nurse, who often acts as the keyworker, can help. The decision should not be rushed by either the team or family.

Cancer Research UK says teams plan for the baby to be born as close to the due date as possible, with induction or caesarean section decided by the treatment plan. Breast cancer has never been known to spread to a baby, though the placenta is examined because very rarely cancer cells can reach it. If the baby is likely to arrive early, steroid injections may be offered to help the baby's lungs.

Breastfeeding depends on the treatment: it is usually possible after surgery or past chemotherapy, but not while having chemotherapy, tamoxifen or trastuzumab. Reliable non-hormonal contraception is advised during treatment. The RCOG notes that for breast cancer, pregnancy after treatment does not appear to increase the chance of the cancer returning, and women are usually advised to wait two years before conceiving.