Greater absolute risk for all subtypes of breast cancer in the US than Malaysia

Abstract

Hormone receptor (HR) negative breast cancers are relatively more common in low-risk than high-risk countries and/or populations. However, the absolute variations between these different populations are not well established given the limited number of cancer registries with incidence rate data by breast cancer subtype. We, therefore, used two unique population-based resources with molecular data to compare incidence rates for the 'intrinsic' breast cancer subtypes between a low-risk Asian population in Malaysia and high-risk non-Hispanic white population in the National Cancer Institute's surveillance, epidemiology, and end results 18 registries database (SEER 18). The intrinsic breast cancer subtypes were recapitulated with the joint expression of the HRs (estrogen receptor and progesterone receptor) and human epidermal growth factor receptor-2 (HER2). Invasive breast cancer incidence rates overall were fivefold greater in SEER 18 than in Malaysia. The majority of breast cancers were HR-positive in SEER 18 and HR-negative in Malaysia. Notwithstanding the greater relative distribution for HR-negative cancers in Malaysia, there was a greater absolute risk for all subtypes in SEER 18; incidence rates were nearly 7-fold higher for HR-positive and 2-fold higher for HR-negative cancers in SEER 18. Despite the well-established relative breast cancer differences between low-risk and high-risk countries and/or populations, there was a greater absolute risk for HR-positive and HR-negative subtypes in the US than Malaysia. Additional analytical studies are sorely needed to determine the factors responsible for the elevated risk of all subtypes of breast cancer in high-risk countries like the United States.

Fig. 1

Age-specific incidence rates per 100,000 woman-years (or women per year) comparing women in Sarawak, Malaysia to the National Cancer Institute’s surveillance, epidemiology, and end results 18 registries database (SEER 18), stratified by estrogen receptor (ER) expression. a Non-Hispanic white (NHW) women in SEER 18 for the years 2003–2011 b Asian/Pacific Islander (API) women in SEER 18 for the years 2003–2011 c Malaysian women in Sarawak, cases restricted to the years 2003–2011

Fig. 2

Age-specific incidence rates per 100,000 woman-years (or women per year) and incidence rate ratios and 95 % confidence intervals comparing women in Sarawak, Malaysia and US Asian/Pacific Islanders (API) to non-Hispanic white (NHW) in SEER18, stratified by molecular subtype defined as a HR-positive/HER2-negative (HR +/HER2−; ER or PR positive and HER2 negative) cases for NHW, API women in SEER18 (restricted to 2010–2011), and Sarawak, Malaysia data (restricted to the years 2008–2011); b HR-positive/HER2-positive (HR +/HER2 + ; ER or PR positive and HER2 positive) cases; c HR-negative/HER2-positive (HR−/HER2 + ; ER and PR negative and HER2 positive) cases; d HR-negative/HER2-negative (HR−/HER2−; ER, PR and HER2 negative) cases