Cancer develops during ~1 in every 1000 pregnancies. Of all the cancers that occur in women, fewer than 1% occur in pregnant women. The four cancers most commonly developing during pregnancy are cervical cancer, breast cancer, melanoma, and lymphomas (particularly Hodgkin's lymphoma); however, virtually every form of cancer has been reported in pregnant women (Table 31-1). In addition to cancers developing in other organs of the mother, gestational trophoblastic tumors can arise from the placenta. The problem of cancer in a pregnant woman is complex. One must take into account the possible influence of the pregnancy on the natural history of the cancer, the effects of the diagnostic and staging procedures, and the treatments of the cancer on both the mother and the developing fetus. These issues may lead to dilemmas: what is best for the mother may be harmful to the fetus, and what is best for the fetus may be harmful to the mother.
TABLE 31-1INCIDENCE OF MALIGNANT TUMORS DURING GESTATION |Favorite Table|Download (.pdf) TABLE 31-1INCIDENCE OF MALIGNANT TUMORS DURING GESTATION
|TUMOR TYPE ||INCIDENCE PER 10,000 PREGNANCIESa ||% OF CASESb |
|Breast cancer ||1–3 ||25 |
|Cervical cancer ||1.2–4.5 ||25 |
|Thyroid cancer ||1.2 ||15 |
|Hodgkin's disease ||1.6 ||10 |
|Melanoma ||1–2.6 ||8 |
|Ovarian cancer ||0.8 ||2 |
|All sites ||10 ||100 |
Another complicating issue in women who develop cancer during pregnancy is that many of the early symptoms of cancer are ignored in pregnant women. The many changes in a woman's body during pregnancy dull one's senses to changes that may be related to an underlying disease rather than the pregnancy. Thus, many cancers that occur in pregnancy present in advanced stages.
As a general rule, one should assume that no diagnostic or therapeutic intervention is safe in the first trimester of pregnancy other than surgery. If the mother develops life-threatening complications during the first trimester that require radiation therapy or systemic chemotherapy and these interventions cannot be safely delayed, a recommendation should be made for an abortion. Indeed, radiation, even in the form of diagnostic radiography, should be avoided throughout pregnancy. No exposure to radiation is safe, and efforts to shield the fetus with barriers placed on the abdomen cannot block internal scatter radiation. It is safest to omit radiation exposure of any kind. Fortunately, its use is seldom an essential component of treatment before delivery.
Chemotherapy exposure is also to be avoided, if at all possible. It should never be given in the first trimester; a ...