Cancer develops during ∼1 in every 1000 pregnancies. Of all the cancers that occur in women, less 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 e6-1). 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. Theese 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 e6-1 Incidence of Malignant Tumors During Gestation
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Table e6-1 Incidence of Malignant Tumors During Gestation
|Tumor Type||Incidence per 10,000 Pregnanciesa||% of Casesb|
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 variety of single agents and combinations have been given in the second and third trimesters, without a high frequency of catastrophic effects to the pregnancy or the fetus, but data on safety are sparse. Maternal factors that may influence the pharmacology of chemotherapeutic agents include the 50% increase in plasma volume, altered absorption and protein binding, increased glomerular filtration rate, increased hepatic mixed function oxidase activity, and third space created by amniotic fluid. The fetus is protected from some agents by placental expression of drug efflux pumps, but decreased fetal hepatic mixed function oxidase and glucuronidation activity may prolong the half-life of agents that do cross the placenta. A database on the risks associated with individual chemotherapy agents is available on the Internet (www.motherisk.org).
The optimal management strategies have not been developed based on prospective clinical trials. Instead, a guiding principle has been to delay therapeutic interventions until as late as possible during the pregnancy. Delivery is recommended at 32 weeks. By and large, this approach minimizes exposure of the child to noxious cancer treatments, spares the mother complications of pregnancy, and is generally accomplished without an adverse impact on treatment outcome. Pregnancy appears to have little or no impact on the natural history of malignancies, despite the hormonal influences. Spread of the mother's cancer to the fetus (so-called vertical transmission) is exceedingly rare.
The incidence of cervical cancer in pregnant women is roughly comparable to that of age-matched controls who are not pregnant. Invasive cervical cancer develops at a rate of about 0.45 in 1000 live births and carcinoma in situ is seen in 1 in 750 pregnancies. About 1% of women diagnosed with cervical cancer are pregnant at the time of diagnosis. Early signs of cervical cancer include vaginal spotting or discharge, pain, and postcoital bleeding that are also common features of pregnancy. Early visual changes in the cervix related to invasive cancer can be mistaken for cervical decidualization or ectropion (columnar epithelium on the cervix) due to pregnancy. Women diagnosed with cervical cancer during pregnancy report having had symptoms for 4.5 months on average.
Human papillomavirus (HPV) types 16 and 18 account for about 70% of cervical cancer. The rate of carriage of these serotypes can be reduced with the use of vaccination before exposure. Screening is recommended at the first prenatal visit and 6 weeks postpartum. The rate of cytologic abnormalities on Pap smear in pregnant women is about 5–8% and is not much different than the rate in nonpregnant women of the same age. Consensus guidelines dictate that specific tests are indicated based on the level of atypia seen on Pap smear. Atypical squamous cells of unknown significance (ASCUS) generally trigger HPV testing with colposcopy reserved for the subset of women with a high-risk HPV-type infection. By contrast, the presence of dysplasia is considered an indication for colposcopy regardless of HPV type. Women with either low- or high-grade squamous intraepithelial lesions (LSIL or HSIL) and HIV-infected women with ASCUS are recommended for colposcopy.
At colposcopy, any areas suspicious for invasive disease are biopsied. However, ...