Abstract PS1-18: Pregnancy-associated breast cancer: Does timing of presentation affect outcome? (2021)

Abstract Background: Pregnancy-associated breast cancer (PABC) comprises breast cancer diagnosed during the gestational period or within the first year post-partum. PABC is associated with worse prognosis, especially for women diagnosed in the postpartum period. Methods: This is an IRB-approved retrospective review of an institutional database of women with stage 0-III PABC diagnosed between 1992 and 2019. Clinicopathologic features, treatments, and clinical outcomes were compared between women who were diagnosed with PABC during pregnancy and those who were diagnosed during lactation (1-12 months after delivery). Comparisons were made using Fisher’s exact tests and chi-square tests of independence. Results: A total of 341 women were identified; 131 (38%) diagnosed during pregnancy (pregnancy associated, PA) and 210 (62%) diagnosed post-partum during lactation (lactation associated, LA). Median age for the cohort was 36 (25-46). Median follow-up was 73 months (range, 11-325). Among women with PA diagnoses, 35% (n = 46) presented with breast masses during first trimester, 32% (n = 42) and 33% (n = 43) presented during second and third trimester, respectively; 28% (n = 36) of pregnancies ended in miscarriage or abortion. Fifty-five percent (n = 116) of LA diagnoses were within 6 months of delivery while 44% (n = 92) were between 6-12 months of delivery. The study population was Caucasian (n = 272, 80%), Black (n=26, 7.6%) and Asian (n = 27, 7.9%). Presenting T-stage, N-stage, and AJCC stage were similar between groups. HR+/HER-2-was the most common subtype in both groups (PA n = 49, 37% vs LA n = 71, 34%, p = 0.6). Distribution of other breast cancer receptor profiles were similar between groups (Table). Chemotherapy was administered to 94% (n = 321) of women; 229, 67% as adjuvant and 92, 27% as neoadjuvant (NAC). 72% of women received ddAC-T. Median time to chemo was 3 weeks (range 1-13) for NAC compared to 4 weeks (range 1-16) for adjuvant. Breast cancer treatment was deferred until after delivery for the PA group in 85 women, 65%. Median time from histologic diagnosis to any treatment was 4 weeks (range, 1-22) for PA group and 4 weeks (range 1-17) for LA group. Radiation therapy was received by most women (n = 194, 57%). Endocrine therapy receipt was also common (n = 168, 93% of women with hormone receptor (HR) positive tumors). Patterns of recurrence were similar between groups with most patients in both groups experiencing no recurrence (PA n = 82, 63% vs LA n = 158, 75%, p = 0.10). Differences were observed in disease status with PA having higher rates of women alive with disease (PA n = 16, 12% vs LA n = 12, 5.7%, p = 0.002) and a lower rate of women with no evidence of disease (PA n = 87, 66% vs LA n = 172, 82%, p = 0.002). Conclusions: Clinicopathologic features were similar between women in both PA and LA groups. Despite these similarities, PA appeared to be associated with higher rates of women alive with disease and lower rates of women with no evidence of disease. Although median time from histologic diagnosis to treatment was similar between PA and LA groups, 65% of women in the PA group had treatment delayed until after delivery, which could potentially impact oncologic outcomes. This highlights the balance between fetal and maternal factors in treatment decisions including possible patient or physician reluctance to treat during pregnancy. Further study is necessary to evaluate this finding. Table 1. Clinicopathologic features and outcomes associated with PABCCharacteristicPregnancy Associated, n=131*Lactation Associated, n=210*p-value**Presenting T02 (1.5%)2 (1.0%)0.3147 (36%)98 (47%)267 (51%)85 (40%)310 (7.6%)19 (9.0%)45 (3.8%)6 (2.9%)Presenting N Stage054 (41%)97 (46%)0.2177 (59%)109 (52%)20 (0%)4 (1.9%)AJCC Stage02 (1.5%)2 (1.0%)0.5126 (20%)54 (26%)261 (47%)99 (47%)342 (32%)55 (26%)SubtypeTN45 (34%)59 (28%)0.3HR+/HER2-49 (37%)71 (34%)0.6HR+/HER2+21 (16%)30 (14%)0.8HR-/HER2+10 (7.6%)31 (15%)0.072RecurrenceContralateral Breast3 (2.3%)5 (2.4%)0.10Distant33 (25%)31 (15%)Ipsilateral LRR9 (6.9%)13 (6.2%) No Recurrence82 (63%)158 (75%)Simultaneous LRR and Distant4 (3.1%)3 (1.4%)Disease StatusAWD16 (12%)12 (5.7%)0.002DOC3 (2.3%)0 (0%)DOD25 (19%)26 (12%) NED87 (66%)172 (82%)*Statistics presented: n (%); **Statistical tests performed: Fisher's exact test; chi-square test of independence Citation Format: Angelena Crown, Damian McCartan, Michael Curry, Maya Feldman, Sujata Patil, Sabrina Kamer, Shari B Goldfarb, Mary Gemignani. Pregnancy-associated breast cancer: Does timing of presentation affect outcome? [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-18.