Survival analysis of pregnancy-associated breast cancer: multiparous women might have better outcomes

Abstract Purpose: Pregnancy-associated breast cancer (PABC) is an aggressive disease and since China began to encourage childbearing in 2015, the incidence of PABC has increased. The study was to investigate the characteristics and survival rates of PABC patients. Methods: Patients with PABC who underwent surgery at Fudan University, Shanghai Cancer Center, from 2005 to 2018 were enrolled. First, the study divided the population into two groups: first-pregnancy group and non-first pregnancy group. Second, patients were categorized as those having breast cancer during pregnancy with/without an abortion or during the lactation period. Results: Overall, 203 patients were recruited. Since 2016, 63.9% patients were diagnosed with PABC during their second or third pregnancy, while at that time in Shanghai, only 25% of newborns were non-first births. Luminal B accounted for the highest proportion (38.4%), followed by triple-negative breast cancer (30.0%). Compared with the non-first pregnancy group, the first-pregnancy group preferred to delay treatment until the fetus was born (time from initial symptoms to treatment: 6.20 vs. 4.67 m, P=0.106). The patients in the first pregnancy group were presented with 57.0% of HR negative tumors and 26.6% of HER-2 positive tumors, while the HR negative tumors accounted for 47.6% (P=0.281) and the proportion of HER-2 positive tumors was 36.3% (P=0.108) in the non-first pregnancy group. The 3-year disease-free survival rate of the first-pregnancy group was 78.4%, and that of the non-first pregnancy group was 83.7% (P=0.325). Conclusions: Our study proves that the proportion of PABC developed during the second or third pregnancy of women was extremely large relative to the newborn populations. Patients in the first-pregnancy group tended to be presented with less aggressive tumor pathological characteristics but a worse survival outcome than those in the non-first pregnancy group.