Managing Cancer in Pregnancy
Cancer can cause fear and distress for any patient, but when cancer is diagnosed during pregnancy, an expectant mother fears not only for her own health but for the health of her unborn child. Fortunately, ob.gyn.s and multidisciplinary teams have good reason to reassure patients about the likelihood of good outcomes.
Cancer treatment in pregnancy has improved with advancements in imaging and chemotherapy, and while maternal and fetal outcomes of prenatal cancer treatment are not well reported, evidence acquired in recent years from case series and retrospective studies shows that most imaging studies and procedural diagnostic tests – and many treatments – can be performed safely in pregnancy.
Dr. Gautam G. Rao
Decades ago, we avoided CT scans during pregnancy because of concerns about radiation exposure to the fetus, leaving some patients without an accurate staging of their cancer. Today, we have evidence that a CT scan is generally safe in pregnancy. Similarly, the safety of many chemotherapeutic regimens in pregnancy has been documented in recent decades,and the use of chemotherapy during pregnancy has increased progressively. Radiation is also commonly utilized in the management of cancers that may occur during pregnancy, such as breast cancer.1
Considerations of timing are often central to decision-making; chemotherapy and radiotherapy are generally avoided in the first trimester to prevent structural fetal anomalies, for instance, and delaying cancer treatment is often warranted when the patient is a few weeks away from delivery. On occasion, iatrogenic preterm birth is considered when the risks to the mother of delaying a necessary cancer treatment outweigh the risks to the fetus of prematurity.1
Pregnancy termination is rarely indicated, however, and information gathered over the past 2 decades suggests that fetal and placental metastases are rare.1 There is broad agreement that prenatal treatment of cancer in pregnancy should adhere as much as possible to protocols and guidelines for nonpregnant patients and that treatment delays driven by fear of fetal anomalies and miscarriage are unnecessary.
Cancer Incidence, Use of Diagnostic Imaging
Data on the incidence of cancer in pregnancy comes from population-based cancer registries, and unfortunately, these data are not standardized and are often incomplete. Many studies include cancer diagnosed up to 1 year after pregnancy, and some include preinvasive disease. Estimates therefore vary considerably (see Table 1 for a sampling of estimates incidences.)
It has been reported, and often cited in the literature, that invasive malignancy complicates one in 1,000 pregnancies and that the incidence of cancer in pregnancy (invasive and noninvasive malignancies) has been rising over time.8 Increasing maternal age is believed to be playing a role in this rise; as women delay childbearing, they enter the age range in which some cancers become more common. Additionally, improvements in screening and diagnostics have led to earlier cancer detection. The incidence of ovarian neoplasms found during pregnancy has increased, for instance, with the routine use of diagnostic ultrasound in pregnancy.1
Among the studies showing an increased incidence of pregnancy-associated cancer is a population-based study in Australia, which found that from 1994 to 2007 the crude incidence of pregnancy-associated cancer increased from 112.3 to 191.5 per 100,000 pregnancies (P < .001).9 A cohort study in the United States documented an increase in incidence from 75.0 per 100,000 pregnancies in 2002 to 138.5 per 100,000 pregnancies in 2012.10
Overall, the literature shows us that the skin, cervix, and breast are also common sites for malignancy during pregnancy.1 According to a 2022 review, breast cancer during pregnancy is less often hormone receptor–positive and more frequently triple negative compared with age-matched controls.11 The frequencies of other pregnancy-associated cancers appear overall to be similar to that of cancer occurring in all women across their reproductive years.1
Too often, diagnosis is delayed because cancer symptoms can be masked by or can mimic normal physiological changes in pregnancy. For instance, breast cancer can be difficult to diagnose during pregnancy and lactation due to anatomic changes in the breast parenchyma. Several studies published in the 1990s showed that breast cancer presents at a more advanced stage in pregnant patients than in nonpregnant patients because of this delay.1 Skin changes suggestive of melanoma can be attributed to hyperpigmentation of pregnancy, for instance. Several observational studies have suggested that thicker melanomas found in pregnancy may be because of delayed diagnosis.8
It is important that we thoroughly investigate signs and symptoms suggestive of a malignancy and not automatically attribute these symptoms to the pregnancy itself. Cervical biopsy of a mass or lesion suspicious for cervical cancer can be done safely during pregnancy and should not be delayed or deferred.
Fetal radiation exposure from radiologic examinations has long been a concern, but we know today that while the imaging modality should be chosen to minimize fetal radiation exposure, CT scans and even PET scans should be performed if these exams are deemed best for evaluation. Embryonic exposure to a dose of less than 50 mGy is rarely if at all associated with fetal malformations or miscarriage and a radiation dose of 100 mGy may be considered a floor for consideration of therapeutic termination of pregnancy.1,8
CT exams are associated with a fetal dose far less than 50 mGy (see Table 2 for radiation doses).
Magnetic resonance imaging with a magnet strength of 3 Tesla or less in any trimester is not associated with an increased risk of harm to the fetus or in early childhood, but the contrast agent gadolinium should be avoided in pregnancy as it has been associated with an increased risk of stillbirth, neonatal death, and childhood inflammatory, rheumatologic, and infiltrative skin lesions.1,8,12