Australia ranks highly on a list of 81 countries according to the proportion of women diagnosed with breast cancer at an early stage, along with countries including the UK, Canada, the Netherlands and Norway.
A systematic review and meta-analysis of the evidence on stage-specific breast cancer diagnoses, published in JAMA Oncology [link here], found 82.3% of Australian women with breast cancer were diagnosed at stage 1 or 2.
Only 12.1% of Australian women were diagnosed with stage 3 disease and 4.6% with stage 4 disease.
However the global data, from 2.4 million women with breast cancer, found wide variation in the distribution of stage at diagnosis.
Generally, higher proportions of distant metastatic disease were observed in sub-Saharan Africa, Central and South America, and Central and West Asia compared to North America, Europe and Oceania which was represented by Australia and New Zealand.
There were also substantial within-region variations in stage at diagnosis.
“For example, in Central and South America, distant metastatic stage proportion ranged from 5.4% (Puerto Rico) to 23.7% (Costa Rica), whereas in East and South Asia, it ranged from 0.8% (Japan) to 18.1% (Malaysia),” the study said.
The study also found metastatic disease was more likely to be diagnosed in older women compared with younger women.
“At the country level, proportions of distant metastatic stages were substantially higher in older than in younger age groups, at least 2-fold in Australia, Finland, Spain, and Georgia and 3-fold in Israel and Luxembourg.”
“France had a 6 times higher proportion of metastatic stages in the 75 years or older age group compared with those younger than 50 years (5.3% vs 33.9%).”
Lower socioeconomic status was also associated with stage of diagnosis particularly within North America, Oceania, and some North European countries.
“In the US, the proportion of distant stages in the lowest SES group (8.0%) doubled compared with the highest SES population (4.0%). On the other hand, differences were less marked across groups in the UK and the Netherlands.”
The investigators said the implementation of national breast cancer screening programs in recent decades has led to a stage shift toward higher proportions of early-stage cancer diagnoses in many countries.
“Consequently, reductions in mortality rates have been observed over time partly due to an increased diagnosis of more curable in situ or localised cancers coupled with improved breast cancer treatment in the past 4 decades.”
They noted however that the age disparity in late stage diagnoses may be explained by breast cancer screening guidelines not recommending routine mammography screening in women >75 years.
“Therefore, the substantial decrease in late-stage diagnoses that has occurred due to the implementation of screening programmes in recent decades is less evident in this older age group compared with the population included in screening programs.”
The investigators noted that one of the study limitations was the proportion of diagnoses with unknown stage in some countries including in high-resourced countries.
Australia fared fairly well with only 5.5% of diagnoses of unknown stage compared to 10.4% in the UK and 27.0% in Germany.
“Improvements in registration and dissemination of cancer stage and harmonising staging systems to support international comparisons are needed to support effective policies and cancer control plans,” they concluded.