Neoadjuvant Chemotherapy and Prognosis of Pregnancy-Associated Breast Cancer: A Time-Trends Study of the Korean Breast Cancer Registry Database

Purpose: Pregnancy-associated breast cancer (PABC) is rare, and its cause and prognosis are not well known. Additionally, treatment is limited with respect to the risk to the fetus. The purpose of this study was to investigate the characteristics and treatment trends of PABC and the survival rate according to the treatment. Methods: In the Korean Breast Cancer Society Registry database, women younger than 50 years and who were diagnosed with breast cancer from 1996 to 2015 were included. PABC was defined as breast cancer diagnosed during pregnancy or within 1 year after delivery. Results: We examined 411 patients with PABC and 83,381 patients with non-PABC. Over time, the proportions of patients undergoing breast-conserving surgery and sentinel lymph node biopsy increased, and neoadjuvant chemotherapy and radiation therapy administration rates also increased. In the past, the overall survival of patients with PABC was poorer than that of patients with non-PABC, but there was no difference in overall survival rates in more recent years. There was no difference in overall survival rates between patients who received neoadjuvant chemotherapy (hazard ratio [HR], 1.28; 95% confidence interval [CI], 0.66-2.49; p=0.459), but PABC conferred poorer prognosis than non-PABC in patients receiving adjuvant chemotherapy (HR, 1.63; 95% CI, 1.27-2.08; p<0.001). Conclusion: There was no difference in the prognosis between patients with PABC and those with non-PABC receiving neoadjuvant chemotherapy. The increase in neoadjuvant chemotherapy according to current treatment guidelines is expected to improve the survival rate of patients with PABC.