Abstract P5-08-46: Competing causes of death among women with breast cancer in South East Asia: Effects of ethnicity, and age at diagnosis and stage at diagnosis
Authors: Ho P , Rijnberg N , Gernaat SAM , Emaus MJ , Grobbee RDE , Lee SC , Hartman M , Verkooijen HM 
Published: May 2016

Background: Over the past decades, breast cancer survival has improved substantially and many patients die of other, non-breast cancer related causes. In South East Asia, where large ethnic differences exist in stage at presentation and overall survival, causes of death of breast cancer patients have been understudied.

Aim: To examine cause-specific mortality among breast cancer patients in multi-ethnic Singapore and investigate effects of ethnicity, and age and tumor stage at diagnosis.

Methods: Data of women diagnosed with breast cancer between 1990 and 2011 at the National University Hospital in Singapore were retrieved from the hospital-based breast cancer registry. Cause of death was categorized as breast cancer (ICD8 174; ICD9 174; ICD10 C50), cardio- and cerebrovascular disease (ICD8 390 to 459; ICD9 390 to 459; ICD10 I00 to I99), other malignancies (ICD8 140 to 239; ICD9 140 to 239; ICD10 C00 to D48 except codes for death resulting from breast cancer), and death from other causes (all ICD codes except those already listed). Patients with unknown cause of death (n=6) were classified as death from other cause. Chi square statistics were used to compare cause of death distributions.

Results: Of 4108 patients, median age at diagnosis was 51 years (range 21- 98 years). The majority of women were Chinese (n=3223, 78%), followed by Malay (n=517, 12%), Indian (n=257, 6%) and other ethnicities (n=111, 3%). After a median follow-up of 7 years, 1125 (27%) patients died: 910 (81%) patients died of breast cancer, 70 (6%) of cardio- and cerebrovascular disease, 71 (6%) of other malignancies, and 83 (7%) of other causes. Compared with other ethnicities, Malay women most frequently died as a result of breast cancer (n=178, 90%). The highest percentage CVD deaths was observed among Indians (n=7, 11%). Breast cancer accounted for 92% of deaths in women younger than 50 years at diagnosis and for 60% in women older than 65. The proportion of deaths as a result of CVD, other cancer or other causes increased with age. Patients with higher tumor stages at diagnosis were more likely to die of breast cancer (96% of deaths of patients with TNM4 were breast cancer related).

Conclusion: The present study showed that breast cancer is the most important cause of death in breast cancer patients among all ethnic groups, and ages and stages in South East Asia. The highest risk of death due to breast cancer in Malay women might be explained by their presentation at advanced stages and young age at diagnosis. Breast cancer is less likely to be the cause of death in women of Chinese ethnicity, older age at diagnosis and early tumor stage. In these groups more attention for competing causes of death, in particular CVD, should be a priority for the future.

Citation Format: Ho P, Rijnberg N, Gernaat SAM, Emaus MJ, Grobbee RDE, Lee SC, Hartman M, Verkooijen HM. Competing causes of death among women with breast cancer in South East Asia: Effects of ethnicity, and age at diagnosis and stage at diagnosis. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-08-46.