Challenges in managing breast cancer during pregnancy.

Pregnancy-associated breast cancer (PABC) is defined as breast cancer occurring anytime during gestation, lactation or within one year after delivery. The optimal management of pregnant women with breast cancer is challenging and not well established; the main concern is the effect of the drugs on the developing fetus and long-term complications after in utero exposure to anti-cancer drugs. Surgical resection is the mainstay of treatment for early breast cancer diagnosed during pregnancy. Modified radical mastectomy is standard of care in first trimester, whereas breast-conserving surgery (lumpectomy with lymph node dissection) can be performed preferably in the second and third trimester. Of note, breast-conserving surgery is not contraindicated per se during the first trimester, but owing to the potential impact of delaying radiotherapy. Radiation therapy is not favored during pregnancy. Moreover, tamoxifen is contraindicated during pregnancy; the agent has been associated with birth defects in up to 20% of exposures. Chemotherapy is generally contraindicated during the first trimester because of the possible damage to organogenesis. Anthracyclines-based regimens are the most widely used is breast cancer treatment and were been shown to be associated with favourable safety profile when administered during pregnancy. As for taxanes, more limited data is available. The use of trastuzumab is contraindicated during pregnancy, given the apparent risk of oligo- and/or anhydramnios as well as the unknown long-term sequelae on the fetus. It is obvious that, diagnosis of breast cancer during pregnancy adds complexity to cancer treatment recommendations. In all cases, a multidisciplinary therapeutic approach among obstetricians, gynaecologists, surgical oncologists, radiation oncologists, medical oncologists, pediatricians and hematologists is clearly warranted.