Breast cancer surgery during pregnancy.

1127 Background: There is limited literature on breast surgery during pregnancy. We present prospective registry data on 88 breast cancer patients who underwent breast cancer surgery during pregnancy. Methods: The Cancer and Pregnancy Registry is a voluntary international registry that prospectively collects the clinical course, treatment, and disease outcome of women diagnosed with cancer during pregnancy and the perinatal and neonatal outcomes of their children. Results: We identified 88 patients who were diagnosed with breast cancer and had surgery while pregnant. 59 patients (67%) underwent Mastectomy while29 patients (32%) underwent breast conserving surgery (BCS). Out of 43 patients who underwent BCS as their first surgery 13 patients (30.23%) required subsequent mastectomy during pregnancy. 15 patients (34.88%) from the BCS group and 4 patients (8.69%) from the Mastectomy group had positive margins. There was no significant difference between patients who underwent mastectomy vs BCS based on Age (34.67 vs 34.72 P: 0.97), gestational age at surgery (14.05 vs 16.06 P: 0.23) or ER positivity (47.5% vs 46.4% P: 0.93). 2 patients had neo-adjuvant chemotherapy. 17 patients (19.31%) had sentinel lymph node biopsy. 37 patients (42%) had a pregnancy complication. There was no difference in the rate of complication based on mastectomy vs BCS(45.8% vs 34.5% P: 0.31). There was only 1 patient (from mastectomy group) that delivered within 2 weeks of surgery. Of the 17 patients (19.3%) with spontaneous preterm delivery, there was no difference between Mastectomy and BCS group (22% vs 13.2% P: 0.41). Of the 25 patients (28.4%) with birth complications, there was no significant difference between mastectomy vs BCS (30.5% vs 24.1% P: 0.53). There was also no difference in mean birth weight between the groups (2598 grams vs 2672.3 grams P: 0.57). Conclusions: The data supports the safety of breast cancer surgery during pregnancy. In addition, there were no identified adverse effects in patients who underwent BCS as opposed to mastectomy. Of note, only 19% of patients underwent sentinel node biopsy which is considered the standard of care in early breast cancer patients regardless of pregnancy status.