Abstract P4-10-12: Gestational breast cancer in Singapore women
Authors: Tan QT , Wong FY , Alcantara VS , Ganguly R , Loh KW-J 
Published: May 2019

Abstract
Background
Gestational breast cancer (GBC), diagnosed during pregnancy or in the first postpartum year, is expected to rise in incidence due to increasing maternal age. GBC poses unique challenges in diagnosis and treatment as clinicians seek to provide optimal treatment for these young patients without compromising neonatal outcomes. We present our retrospective findings from the first study on gestational breast cancer in Singapore.
Methods
We performed a retrospective study on 88 patients with gestational breast cancer diagnosed from April 2003 to April 2017 at three centres in Singapore. Demographic details, tumour histopathological characteristics, stage, treatment and outcomes data was collected and analysed.
Results
Eighty-eight patients were diagnosed with GBC at a median age of 35.9 years (26-43 years). Fifty (56.8%) were diagnosed intrapartum and 38 (43.2%) were diagnosed postpartum. Seventeen (19.8%) had a family history of breast cancer but none had proven BRCA mutation. Seventeen patients (19.3%) presented with stage 1, 36 (40.9%) with stage 2, 25 (28.4%) with stage 3, 5 (5.7%) with stage 4 disease. Seventeen patients underwent termination of pregnancy (27.9% of patients diagnosed during pregnancy). Seventeen (19.3%) of patients received neoadjuvant chemotherapy, 8 of whom received it during pregnancy. Forty-eight (54.5%) received adjuvant chemotherapy, 4 of whom received it during pregnancy. Two patients received palliative chemotherapy during pregnancy. Aside from one case of hearing impairment, there was no other documented neonatal complication for patients who received intrapartum chemotherapy.
The 5-year and 10-year overall survival (OS) was 80% and 66%. According to the Singapore National Cancer Registry, the 5-year OS for women younger than 44 years of age was 88.9%, therefore suggesting a lower OS in patients with GBC. The 5-year and 10 year disease-free survival (DFS) of our patients was 73% and 60% respectively. Diagnosis of cancer postpartum conferred a higher risk (hazard ratio (95%CI) 1.86 (0.55, 6.28) of mortality compared to those diagnosed intrapartum. Univariate Cox proportional hazard regression model showed that nodal positivity and clinical stage were significantly associated with DFS while only clinical stage was significantly associated with OS. Race was found to affect survival with Malay patients having a lower DFS compared to Chinese patients.
Conclusion
GBC patients in Singapore have a lower survival rate. Diagnosis of cancer postpartum confers a higher risk of mortality. This might be due to a delay in diagnosis and treatment. Malay patients have a lower survival compared to Chinese patients. Studies into genetic and social factors might shed light on how ethnicity affects survival of these patients.
Citation Format: Tan QT, Wong FY, Alcantara VS, Ganguly R, Loh KW-J. Gestational breast cancer in Singapore women [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-10-12.