January 18, 2024 by Cancer Rose
Publication JAMA
Caswell-Jin JL, Sun LP, Munoz D, et al. Analysis of Breast Cancer Mortality in the US—1975 to 2019. JAMA. 2024;331(3):233–241. doi:10.1001/jama.2023.25881
Synthesis by Cancer Rose, 18/01/2024
Question
What are the relative associations of breast cancer screening, treatment of stage I to III breast cancer, and treatment of metastatic breast cancer with improved breast cancer mortality in the US between 1975 and 2019?
Results
Improvements in treatment and screening after 1975 were associated with a 58% reduction in breast cancer mortality in 2019, from an estimated 64 deaths without intervention to 27 per 100 000 women (age adjusted). Approximately 29% of this reduction was associated with treating metastatic breast cancer, 25% with screening, and 47% with treating stage I to III breast cancer.
Significance and conclusion
Based on 4 simulation models, breast cancer screening, treatment of stage I to III breast cancer, and treatment of metastatic breast cancer were each associated with reduced breast cancer mortality between 1975 and 2019 in the US.
Limitations and criticisms
According to the authors:
This study has several limitations.
Firstly, the accuracy of the model depends on the assumptions made, for which exact data were not always available.
Secondly, the models did not take into account potential disparities, for example, by age, race and ethnicity, in the spread or effectiveness of screening and treatment. Disparities in breast cancer screening, as well as the promptness and quality of treatment, may contribute to differential breast cancer mortality rates.
Thirdly, treatment costs and their links with outcomes were not included in the models.
Critical review of Cancer Rose, by Dr V.Robert, statistician
Above all, there is at least one major problem: the estimated reductions in mortality are made in relation to the mortality without intervention (in the absence of screening and chemotherapy) estimated by the models.
To obtain this mortality without intervention in 2019, one applies the lethality of 1975 (before screening and chemotherapy, i.e. without intervention) to the cancers of 2019 (the process is a little more complex, but it basically equals to this).
Since the incidence of cancers has risen as a result of screening, this leads to a theoretical increase in mortality, from 48 deaths / 100,000 (actual mortality without intervention) in 1975 to 65 deaths / 100,000 (mortality without intervention estimated by the model) in 2019.
The problem is that the increase in cancer incidence is essentially due to screening, and therefore largely to over-diagnosis, whose lethality is zero. The lethality modelled for 1975 is therefore meaningless for cancers in 2019, which include over-diagnosis.
A recently published meta-analysis showed no gain in lifespan through screening, raising more disturbing questions about the relevance of maintaining and especially promoting screening without informing the population-.
Read here: https://cancer-rose.fr/en/2023/09/08/screenings-dont-extend-lifespan/