Ethnic Differences in Survival after Breast Cancer in South East Asia

Nirmala Bhoo-Pathy,Awang M Bulgiba,Hans-Olov Adami,Soo-Chin Lee,Siew-Eng Lim,Cheng-Har Yip,Nur Aishah Taib,Helena M Verkooijen,Philip Iau,Nakul Saxena,Mikael Hartman,Syed A Aziz

doi:10.1371/journal.pone.0030995

Abstract

BackgroundThe burden of breast cancer in Asia is escalating. We evaluated the impact of ethnicity on survival after breast cancer in the multi-ethnic region of South East Asia.Methodology/Principal FindingsUsing the Singapore-Malaysia hospital-based breast cancer registry, we analyzed the association between ethnicity and mortality following breast cancer in 5,264 patients diagnosed between 1990 and 2007 (Chinese: 71.6%, Malay: 18.4%, Indian: 10.0%). We compared survival rates between ethnic groups and calculated adjusted hazard ratios (HR) to estimate the independent effect of ethnicity on survival. Malays (n = 968) presented at a significantly younger age, with larger tumors, and at later stages than the Chinese and Indians. Malays were also more likely to have axillary lymph node metastasis at similar tumor sizes and to have hormone receptor negative and poorly differentiated tumors. Five year overall survival was highest in the Chinese women (75.8%; 95%CI: 74.4%–77.3%) followed by Indians (68.0%; 95%CI: 63.8%–72.2%), and Malays (58.5%; 95%CI: 55.2%–61.7%). Compared to the Chinese, Malay ethnicity was associated with significantly higher risk of all-cause mortality (HR: 1.34; 95%CI: 1.19–1.51), independent of age, stage, tumor characteristics and treatment. Indian ethnicity was not significantly associated with risk of mortality after breast cancer compared to the Chinese (HR: 1.14; 95%CI: 0.98–1.34).ConclusionIn South East Asia, Malay ethnicity is independently associated with poorer survival after breast cancer. Research into underlying reasons, potentially including variations in tumor biology, psychosocial factors, treatment responsiveness and lifestyle after diagnosis, is warranted.

Highlights

In contrast to the West, where breast cancer incidence rates have plateaued or even decreased [1,2], the incidence of breast cancer is rapidly escalating in Asia
In South East Asia, Malay ethnicity is independently associated with poorer survival after breast cancer
Using a large multicenter hospital-based cohort of breast cancer patients from Malaysia and Singapore, we investigated the impact of ethnicity on survival after breast cancer, and possible mechanisms to explain the survival disparities

Summary

Introduction

In contrast to the West, where breast cancer incidence rates have plateaued or even decreased [1,2], the incidence of breast cancer is rapidly escalating in Asia. The impact of ethnicity on survival after breast cancer in Asian settings has hardly been studied. In Malaysia and Singapore, multiethnic nations comprising 3 major ethnic groups namely Malays, Chinese and Indians [6,7], age-standardized incidence rates of breast cancer differ substantially. Whilst Malay women have the lowest incidence of breast cancer, there is some evidence of poorer prognosis compared to their Chinese and Indian counterparts [8]. It remains unclear whether stage at diagnosis, tumor characteristics, or treatment explains the survival disparities.

Results

Discussion

Conclusion