Abstract
IMPORTANCE: In Australia and other high-income countries diagnosis of the most curable stages of breast cancer, early breast cancer (EBC), in women by population based mammographic screening and administering postsurgical adjuvant endocrine and chemotherapy (adjuvant therapy), began in the 1990s. In only a few populations have long term trends in the incidence of breast cancer stages at diagnosis been measured and the advanced stages of breast cancer have increased or remained stable. Therefore, mammographic screening could not have caused these declines in those populations, which include Victoria Australia. In contrast, in Victoria adjuvant therapy use can explain this decline.
OBJECTIVE: To examine whether mammographic screening has continued to have no impact on breast cancer mortality by updating the 1986-2013 Victorian State report to 2019.
DESIGN, SETTING, AND PARTICIPANTS: Data from January 1, 1982, to December 31, 2019, were obtained from the Victorian Cancer Registry (VCR) based in the Cancer Council Victoria (TCCV) and VCR based breast cancer management surveys for all Victorian women with invasive breast cancer.
EXPOSURES: Participation in BreastScreen Victoria and receipt of adjuvant therapy after surgery for EBC.
MAIN OUTCOMES AND MEASURES: Data were analysed for associations between trends in female crude breast cancer mortality, downstaging by mammographic screening and adjuvant therapy administration.
RESULTS: The VCR registered 30,350 women with invasive breast cancer between January 1, 2013, and December 31, 2019, reporting these incidences by the end of the year following registration. The crude incidence of advanced breast cancer combined tumour, node, metastases (TNM) stages 3 and 4 increased by 22% from 31 per 100,000 women in 2013 to 38 per 100,000 women in 2019, his is triple what it was in 1986, before population based mammographic screening commenced in Victoria.
CONCLUSIONS AND RELEVANCE: Mammographic screening did not down-stage breast cancer in Victoria from TNM advanced stages 3 and 4 to early stages TNM 1 and 2 between 2013 and 2019. Adjuvant therapy uptake by women with EBC has continued and is associated with all of the decline in Victorian breast cancer mortality since population based mammographic screening began in 1993.