Abstract
BackgroundBreast cancer is the leading cause of cancer morbidity among Shanghai and Hong Kong women, which contributes to 20–25% of new female cancer incidents. This study aimed to describe the temporal trend of breast cancer and interpret the potential effects on the observed secular trends.MethodsCancer incident data were obtained from the cancer registries. Age-standardized incidence rate was computed by the direct method using the World population of 2000. Average annual percentage change (AAPC) in incidence rate was estimated by the Joinpoint regression. Age, period and cohort effects were assessed by using a log-linear model with Poisson regression.ResultsDuring 1976–2009, an increasing trend of breast cancer incidence was observed, with an AAPC of 1.73 [95% confidence interval (CI): 1.54–1.92)] for women in Hong Kong and 2.83 (95% CI, 2.26–3.40) in Shanghai. Greater upward trends were revealed in Shanghai women aged 50 years old or above (AAPC = 3.09; 95% CI, 1.48–4.73). Using age at 50 years old as cut-point, strong birth cohort effects were shown in both pre- and post-menopausal women, though a more remarkable effect was suggested in Shanghai post-menopausal women. No evidence for a period effect was indicated.ConclusionsIncidence rate of breast cancer has been more speedy in Shanghai post-menopausal women than that of the Hong Kong women over the past 30 years. Decreased birth rate and increasing environmental exposures (e.g., light-at-night) over successive generations may have constituted major impacts on the birth cohort effects, especially for the post-menopausal breast cancer; further analytic studies are warranted.
Highlights
Breast cancer is the leading cause of cancer morbidity among Shanghai and Hong Kong women, which contributes to 20–25% of new female cancer incidents
This study described the temporal trend of breast cancer among Hong Kong and Shanghai women and assessed the potential effects contributing to the increasing trend in pre- and post-menopausal breast cancers by using a novel approach of age-period-cohort modeling (APC) developed by Rutherford et al [8]
The increasing trends were similar for Hong Kong and Shanghai women aged among 20–49 years-old (p = 0.58), with an annual percentage change (AAPC) of 2.06 and 2.64, respectively
Summary
Breast cancer is the leading cause of cancer morbidity among Shanghai and Hong Kong women, which contributes to 20–25% of new female cancer incidents. Wang et al BMC Cancer (2017) 17:362 pattern and ageing of their population [6, 7]; these are the established risk factors that may have contributed greatly to the increasing rate of breast cancer incidence. Previous time trend studies on breast cancer were based on the overall analysis that might have masked the actual trends of pre-menopausal (early age onset) and post-menopausal breast cancer, between they represent different disease entities with various etiology [4]. This study described the temporal trend of breast cancer among Hong Kong and Shanghai women and assessed the potential effects contributing to the increasing trend in pre- and post-menopausal breast cancers by using a novel approach of age-period-cohort modeling (APC) developed by Rutherford et al [8]
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