NEWS & PERSPECTIVE
Early mammography screening substantially decreases the risk of advanced and fatal breast cancers
Breast cancer is a prevalent invasive cancer in women, and one of the leading causes of death worldwide.1 However, there is a significant global variation in breast cancer survival rates. The CONCORD study demonstrated the highest survival rates of 80% in North America, Sweden, and Japan, followed by an estimated 60% in middle-income countries and below 40% in low-income countries.2 Employing early-stage cancer detection strategy has been suggested to account for the higher survival rates in breast cancer patients. Furthermore, according to the World Health Organization (WHO), the five-year survival rate for early localized breast cancer is ≤80% for women who had early breast cancer detection. To date, mammography screening has proven to be the most effective screening method for breast cancer.3 A recent 10-year breast cancer mortality study involving 549,091 women reported that early mammography screening contributed to the reduction of breast cancer deaths by 41%.4
Breast cancer is currently the leading cancer for women worldwide, with a higher frequency of women diagnosed with late-stage breast cancer.2 Lower survival rates, ranging from 10-40%, were observed in the majority of breast cancer patients diagnosed only at the advanced stage of the diseases.1 While WHO promotes the implementation of early breast cancer screening programs for breast cancer control.1 With the recent establishments of adjuvant breast cancer therapies, there is a growing doubt on the relevance of early breast cancer screening strategies towards reducing breast cancer mortality.5
A new study published by Dr. Stephen Duffy, from the Queen Mary University of London Center for Cancer Prevention and Dr. László Tabár, from the mammography department in the Falun Central Hospital in Sweden, highlighted the benefits of early breast cancer screening despite current improvements in breast cancer treatment. As such, researches led by Dr. Duffy and Dr. Tabár aimed to evaluate the effectiveness of mammography screening as a strategy to reduce the 10-year risk of death in breast cancer patients residing in 9 Swedish counties.4
Both the Swedish Cancer Registry and Swedish National Board of Health and Welfare provided patient data on breast cancer diagnoses and dates of deaths and causes, respectively. The study consisted of 549,091 women, which included 30% of the Swedish screening-eligible population. Breast cancer screening utilizing 2‐view mammography defined individuals with advanced breast cancer as an invasive disease involving tumors measuring >20mm, and ≥4 metastatic axillary lymph nodes.4
Classification of individuals receiving mammography screening involved meeting the requirements of completing majority screening sessions as per protocol. Women aged 40 to 54 years had to attend mammography screening every 18 months and every 24 months for women aged 55 to 69 years every 24 months. The average range of observation was 13 (range 7-16) years for patients with a fatal disease and 22 (range 16-25) years for patients with advanced disease. The total number of fatal diseases were 2,473 (0.45%) cases and 9,737 (1.8%) cases for advanced-stage breast cancer.4
Both a decline by 41% in the risk from dying of breast cancer (RR=0.59; 95% CI: 0.51-0.68; p<0.001) and a reduction of 25% in advanced breast cancers (RR=0.75; 95% CI: 0.66-0.84; p<0.001) was observed within 10 years of diagnosis for women who participated in the mammography screening. The conservative estimate adjusted for potential lead time and self‐selection biases was still significant at 34% (RR=0.66; 95% CI: 0.55-0.79; p<0.001). Despite the large patient population, statistical precision and long-term follow-up, there was an absence of data about the mammography screenings from private facilities.4
Dr. Duffy commented, “This study showed that participation in breast cancer screening substantially reduced the risk of having fatal breast cancer. Besides, because the comparison of participating with non-participating persons was contemporaneous with mammography screening and breast cancer treatment belonging to the same time, it was not affected by potential changes in the treatment of breast cancer over time.”
The study demonstrated substantial positive treatment outcomes associated with early-stage breast cancer detection through mammography screening and the feasibility of collecting critical screening data on a national basis. To conclude, early mammography screening still plays a vital role in improving the mortality rate for women with breast cancer in a period in which modern adjuvant therapies are available.
- WHO Position Paper on Mammography Screening. Geneva: World Health Organization; 2014.
- Coleman M et al. Cancer survival in five continents: a worldwide population-based study (CONCORD). The Lancet Oncology.2008;9(8):730-756.
- Tabar L et al. The incidence of fatal breast cancer measures the increased effectiveness of therapy in women participating in mammography screening. Cancer. 2019; 125:515‐523.
- Duffy S et al. Mammography screening reduces rates of advanced and fatal breast cancers: Results in 549,091 women. Cancer.2020.
- Giordano S et al. Systemic Therapy for Patients with advanced human epidermal growth factor receptor 2–positive breast cancer: American Society of Clinical Oncology Clinical Practice Guideline. Journal of Clinical Oncology. 2014;32(19):2078-2099.
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