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Mammography Does Not Reduce Breast Cancer Mortality Rate

Although mammography is the main examination to diagnose breast cancer, the recommendation for routine mammography every year needs to be reviewed because it does not reduce breast cancer mortality and can increase the risk of overdiagnosis and overtreatment.

Breast cancer is the most common cancer in women in the world and often causes death. The incidence of breast cancer is decreasing, especially in developed countries, but is increasing in developing countries. Breast cancer mortality declined sharply in developed countries from 1988-1995. Decreased mortality is believed to be due to patient awareness, screening, and improved patient management, including the speed of detection, intervention, and postoperative treatment.

Several studies in the 1980s suggested that mammography screening in women aged 40-74 years can reduce breast cancer mortality by 25-31%. However, in Canada in 2002, a study found that there were no significant changes in mortality in the group that received mammography screening compared to physical examination screening.

2D and 3D Breast Cancer Imaging Mammography
2D and 3D Breast Cancer Imaging Mammography
(source pict: https://moffitt.org/)



The roles of mammography in breast cancer

Before the use of mammography as a diagnostic modality, breast cancer was diagnosed by physical palpation examination. Therefore, the results of breast cancer therapy had a poor prognosis due to the late detection of the disease.

Mammography is one type of X-ray imaging specifically for viewing breast images. During the mammography procedure, breast compression is performed to make it flat, so that it can show the glands optimally. If there are irregular lesions, indistinct boundaries, and hyperdensity, it is necessary to suspect malignant lesions and need further examination.

The rationalization of mammography as a screening aims to detect breast cancer that is still early and cannot be palpated on physical examination.

The European Union Council and The International Agency for Research on Cancer recommend the use of screening mammography annually in women aged 50-69 years, whereas the Society of Breast Imaging and the Breast Imaging Commission of the American College of Radiology recommend screening mammography from the age of 40 every year.


Effectiveness of Mammography Screening on Breast Cancer Mortality

Moller et al., 2019, conducted a population-based cohort study to see the effects of mammography screening on breast cancer mortality. There was a decrease in breast cancer mortality both in the group of women screened and not screened by mammography. Moreover, mortality rates were not significantly different between the two groups. This result can be explained by doing this study, all participants who screened or not get an education so that there is an increase in self-awareness of breast cancer. This condition is also supported by the establishment of a breast cancer diagnosis and treatment center in each country following the study.

A meta-analysis of seven studies of the effectiveness of mammography screening in breast cancer mortality found that mortality from breast cancer is an unreliable outcome that is biased in the benefits of breast mammography screening, mainly due to misclassification of differential causes of death. In three studies that carried out adequate randomization, found no screening effect on the mortality of all cancers, including breast cancer after 10 years (RR 1.02, 95% CI 0.95-1.10) or on all causes of death after 13 years (RR 0.99, 95% CI 0.95 to 1.03).

This meta-analysis also found the possibility of overdiagnosis as a consequence of screening mammography and can be harmful to patients. Overdiagnosis and overtreatment rates in studies in the meta-analysis reached 30%. False-positive diagnoses are harmful to the patient because they can cause psychological stress to the patient, both at the time of diagnosis and years after the woman is declared free of cancer.

Whereas the retrospective study conducted by Engel et al. obtained different results. This study was conducted by examining all-cause mortality due to non-routine mammography examinations each year before being diagnosed with breast cancer. In this study, there was a 2-3-fold increase in all-cause mortality in women who did not undergo mammography examinations annually for 5 years. This study also found results in a progressive increase in mortality if the patient did not routinely perform mammography examinations. This study suggested that mammography examinations should be carried out before the diagnosis of breast cancer to improve survival. This study had limited short follow-up time and many side effects from treatment, such as radiation exposure. In addition, this cohort study falls within the scope of a small sample.


References
1. Autier P, Boniol M. Mammography screening: a major issue in medicine. European Journal of Cancer. 2018;90:34-62.
2. Shetty MK. Screening for breast cancer with mammography: current status and an overview. Indian J Surg Oncl. 2010;1(3):218-223.
3. Dongola N. Mammography in breast cancer. [Medscape]. [internet]. Available from: https://emedicine.medscape.com/article/346529-overview#a2
4. Bleyer A, Blaines C, Miller AB. Impact of Screening mammography on breast cancer mortality. Int J Cancer. 2016;2016;138(8):2003-12.
5. Moller MH, Lousdal ML, Kristiansen IS, Stovring H. effect of organized mammography screening on breast cancer mortality: a population-based cohort study in Norway. It J Cancer. 2019;144(4):697-706.
6. Gotzsche PC, Jorgensen KJ. Screening for breast cancer with mammography. Cochrane Library. DOI: 10.1002/14651858.CD001877.pub5
7. Engel JM, Drengler TJS, Stankowski RV, Liang H, Doi SA, Onitilo AA. All-case mortality is decreased in women undergoing annual mammography before breast cancer diagnosis. American Journal of Roentgenology. 2015;204(4):898-902.

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