In addition to establishing the tissue diagnosis of breast cancer, typically, your treating physicians will want to determine the molecular characteristics of the tumor cells. This information helps in counseling with regard to prognosis and, also, to direct the most appropriate course of treatment. Currently, the two features most frequently screened for are ‘hormone receptor status’ and ‘HER2’ status of the tumor cells. Hormone receptor-positive cancers tend to respond well to drugs that target these receptors. Cancers that have multiple copies of the HER2 gene, or have high concentrations of HER2 receptors, are typically more aggressive tumors, associated with rapid growth and increased risk of metastasis. Determination of either hormone receptor or HER2 status can be more difficult during pregnancy, mainly due to the presence of high hormone levels and their effects on circulating blood proteins, but there are diagnostic techniques currently available to help circumvent these interfering effects.
Once the extent of the breast cancer is determined, the ‘stage’ of the disease is assigned for purposes of directing therapy. Detailed discussion of staging is beyond the scope of this review, but as in most cancers, the earlier the stage at diagnosis, the greater the prospects of long-term survival. The overall impression has been that the prognosis for breast cancer detected during pregnancy carries a poorer prognosis than that detected in the nonpregnant state. Recent studies have shown, however, that when women are compared by age, type, and stage of breast cancer, those who are pregnant do as well as those who are not if appropriate treatment is instituted in a timely fashion. Unfortunately, breast cancers found during pregnancy are more likely to be metastatic at the time of detection due to the delay in diagnosis and most studies have shown that 5-year survival of stage III and IV disease is no more than about 10%. Furthermore, some women may choose to delay therapy for fear of harming their babies.
Therapy during pregnancy is best if it is individualized in consultation with an experienced, multidisciplinary support team. In general, recommended treatment in early stage (I and II) disease during pregnancy is surgical. Approaches range from modified radical mastectomy to simple lumpectomy and sentinel node biopsy, and can be followed by chemotherapy. If early stage disease is picked up late in pregnancy, conservative surgery (lumpectomy with lymph node sampling), followed by radiation therapy after delivery, may be an option. Radiation therapy during pregnancy is generally not advised at any time, and especially in first trimester, due to potentially harmful effects on the baby.
When chemotherapy is indicated, the general approach has been to delay this until completion of the first trimester of pregnancy. Selected chemotherapy (such as fluorouracil, adriamycin, and cyclophosphamide) after first trimester is generally not associated with fetal birth defects, but carries a slightly increased risk for premature delivery and pregnancy loss for reasons that are unclear. A few case reports of the use of ‘neoadjuvant’ taxanes (paclitaxel or docetaxel) have been recently published that suggest these agents may also be safe if used in second and third trimesters. Hormonal therapy is generally not offered during pregnancy due to potential fetal risks.
In late stage (III or IV) disease, both patient (and family) and provider are placed in a very difficult position. Prognosis for 5-year survival is poor, but aggressive therapy may also jeopardize the baby. If the diagnosis of late stage disease is made in later pregnancy, early delivery can be considered at a time when the baby is less likely to suffer the more severe consequences of prematurity before starting radiation therapy or chemotherapeutic regimens that might be more dangerous to the baby. Although terminating a pregnancy early is not associated with increased prospects for maternal survival, when late stage cancer is detected early in pregnancy, the woman might consider this option if she wants aggressive therapy but does not want to risk having a baby that might be damaged by the same, or does not want to risk bringing a baby into the world that she will be unlikely to be available to care for over time. On the other hand, some women with very poor prognosis disease may choose to carry their pregnancies without any adjuvant treatment to maximize the chance of a good outcome for their baby.