A rapid rise in hormone receptor-positive and HER2-positive breast cancer subtypes in Southern Thai women: A population-based study in Songkhla

Abstract

The incidence of breast cancer is increasing in low- and middle-income countries, including Thailand. However, its molecular immunohistochemical (M-IHC) subtypes have not been summarized in a population-based cancer registry. Thus, we aimed to estimate the breast cancer incidence and trends based on the hormone receptor and human epidermal growth factor receptor 2 (HER2) status. This cross-sectional study included 2,883 women diagnosed with primary invasive breast cancer between 2009 and 2018 from the Songkhla Cancer Registry. After imputing the missing values of estrogen receptor (ER), progesterone receptor (PR), and HER2 status, the cases were classified into four subtypes: HR+/HER2-, HR+/HER2+, HR-/HER2-, and HR-/HER2+. The age-specific incidence rate of 5-year age groups and age-standardized incidence rate (ASR) were calculated. An age-period-cohort (APC) model was used to describe the effects of age, birth cohort, and period of diagnosis. Finally, the incidence trends were extrapolated to 2030 based on the APC and joinpoint models. The results showed, HR+/HER2- had the highest ASR in breast cancer. The incidence trends of HR+/HER2- and HR+/HER2+ increased with an annual percent change of 5.4% (95%CI: 2.5% to 8.3%) and 10.1% (95%CI: 4.9% to 15.5%), respectively. The rate ratio was high in the younger generation and recent period of diagnosis. The joinpoint and APC model projections showed that the ASR of HR+/HER2- would reach 30.0 and 29.2 cases per 100,000 women, while ASR of the HR+/HER2+ would reach 8.8 and 10.4 cases per 100,000 women in 2030. On the other hand, the incidence trends of the HR-/HER2- and HR-/HER2+ subtypes were stable. The rising trends of HR-positive and a part of HER2-positive breast cancer forecast a dynamicity of the future health care budgeting, resource allocation, and provision of facilities.

Fig 1. The 5-year mean age-specific incidence rates and 95% confidence interval per 100,000 women of the four breast cancer subtypes according to M-IHC.

HR = hormone receptor; HER2 = human epidermal growth factor receptor 2; HR+/HER2- = luminal A-like; HR+/HER2+ = luminal B-like; HR-/HER2- = triple-negative; HR-/HER2+ = HER2-enriched.

Fig 2. The age-period-cohort (APC) trend analysis of the four breast cancer subtypes according to M-IHC in A, B, C, and D.

The three curves in each subfigure, from left to right, represent the incidence rate by age, the rate ratio of incidence by birth-cohort, and year of diagnosis for the reference cohort in blue or reference period in red. The references were the cohort born in 1950 and the diagnosis period of 2009, respectively. Thick lines and the associated thin lines are the three coefficients mentioned previously and 95% confidence intervals. AP-C = Cohort effects modeled with Age-Period component as offset; AC-P = Period effects modeled with Age-Cohort component as offset; HR = hormone receptor; HER2 = human epidermal growth factor receptor 2.

Fig 3. The trends and projection of age-standardized rates per 100,000 women with two methods, joinpoint and age-period-cohort models in A and B of the four breast cancer subtypes according to M-IHC in four different colors.

The incidence rate (y-axis) is on a log scale. Dots connected with thin solid lines in subfigures A and B represent the calculated ASRs from 2009 to 2018. Thick solid lines represent the smooth/modeled ASRs. The extended dashed lines represent the projected trends of ASRs in 2019–2030. HR = hormone receptor; HER2 = human epidermal growth factor receptor 2.