Women who have annual mammograms are less likely to discover advanced-stage breast cancer than those who are screened every two years or less frequently. The finding comes from research from the University of Pittsburgh, in the United States, published in August in the Journal of Clinical Oncology.
To get to conclusionresearchers evaluated information from 8,145 patients diagnosed with breast cancer between 2004 and 2019. The screening interval was considered annual when the exam took place over a period of less than 15 months; biennial if it occurred between 15 and 27 months; or intermittent if it was done after 27 months.
Among those who underwent the exam annually, 9% discovered the disease at an advanced stage; in those who underwent the test every two years, this rate was 14%; and in the intermittent group, 19%. The trend continued regardless of age, race and menopause.
According to the authors comment in the article, these results show the advantage of annual screening for early diagnosis and increased survival. Breast cancer is the second most common type among women, behind only non-melanoma skin cancer. In Brazil, the National Cancer Institute (Inca) projects almost 74 thousand new cases per year between 2023 and 2025.
When discovered at an early stage, the chances of curing breast cancer can reach 95%. And mammography and ultrasound play an essential role in this. To give you an idea, studies indicate that mammography can contribute to reducing breast cancer mortality by up to 40%.
“As with any cancer, the earlier the diagnosis, the greater the chance of a cure. Often, mammography allows the diagnosis to be made before the tumor becomes invasive, for example. In these cases, the chances of cure reach 99.5%. This certainly contrasts greatly with the survival rate of around 60% to 70% of cases diagnosed in more advanced stages”, says breast specialist Danielle Martin Matsumoto, from Hospital Israelita Albert Einstein.
Discrepancies to start the screening
However, although there are more studies demonstrating the benefits of mammographic screening for breast cancer, guidelines recommending at what age and how often women should have this screening are conflicting.
In the United States, the American College of Radiology, the American Cancer Society and other organizations recommend annual mammograms after age 40. The US Preventive Services Task Force — a group of experts that analyzes scientific evidence in preventive medicine and discusses new recommendations — recommends that exams be biannual from the age of 40 onwards.
In Brazil, the situation is even more divergent: the National Cancer Institute (Inca), linked to the Ministry of Health, recommends that breast cancer screening through mammography only occurs every two years, in women aged 50 to 69. years. However, the Brazilian Society of Mastology, the Brazilian College of Radiology and the Brazilian Federation of Gynecology and Obstetrics Associations (Febrasgo) follow the American Cancer Society protocol and recommend annual mammography from the age of 40 onwards.
The authors of the new study point out that about 65 percent of women over age 40 are screened for breast cancer in the U.S., and only about half of them get screened once a year. This is, in part, due to conflicting guidelines on recommended screening intervals.
According to Matsumoto, in Brazil the numbers should be even lower, especially considering women who use the public health network. “In the public system we rarely see women in their 40s diagnosed through screening tests. Most of the time, it happens due to a complaint from the patient, who is able to palpate the tumor itself and seeks help. In supplementary healthcare this is a little calmer and the lack of examination at this age is more associated with the patient’s absence from the routine”, he ponders.
In general, breast cancer grows slowly to moderately, which is why mammography is able to identify it early. “Still, within breast cancers, there are some types that grow faster, are more aggressive and, often, will occur in the interval between screenings. That’s why it’s so important that mammograms are performed annually”, comments the Einstein mastologist.
Younger, more aggressive
Younger patients, under the age of 49, are at greater risk of developing aggressive tumors. One study at the University of São Paulo (USP) analyzed the cases of almost 500 patients aged 40 or younger treated by the Cancer Institute of the State of São Paulo (Icesp) and found that 71% of them had an advanced tumor when diagnosed, and 85.6% reached the diagnosis due to clinical complaints.
This research also showed that the incidence of breast cancer in young women is higher in Brazil than that recorded in other countries. In the United States, only 5% of patients are under 40 years old; around here, it’s 15%. “In developed countries, with a predominantly white population, in general, the average age of breast cancer is 63 years. Less than 20% of patients have cancer before the age of 50 and under the age of 40 it is even rarer, around 5%”, reports Matsumoto.
According to Inca, in 2023 the public health network recorded 60,866 diagnoses of breast cancer in women. Of these, 6,927 (11%) were under 40 years old; 13,576 (22%) between 40 and 49 years old; 15,684 (26%) between 50 and 59 years old; and 24,679 (41%), over 59 years old.
Regarding the guidelines for starting the recommendation of mammographic screening, Inca declared to Agência Einstein that it reaffirms the guidelines in force in Brazil, with the recommendation of screening for women aged 50 to 69, every two years. The organization published a technical note in December 2023 in which it cites a technical-scientific opinion that points out as unjustified the expansion of the use of mammography for asymptomatic women under 50 years old and over 69 years old in the Unified Health System (SUS).
In the document, Inca informs that “although some meta-analyses demonstrate a potential reduction in breast cancer mortality rates in women under the age of 50 who undergo mammographic screening (ranging between 15 and 20%), other published evaluations recently and of moderate-high methodological quality emphasize that there are no statistically significant differences in these rates.”
Possible bottlenecks
In Danielle Matsumoto’s view, when recommending a screening test, it is necessary to take into account that there is a chance of a false positive result. This happens when the person takes the exam, the doctor sees a suspicious finding and needs to investigate whether it is cancer or not, through a biopsy. When this finding is not confirmed as cancer, it is called a false positive.
“The younger the patient, the denser the breasts and the greater the risk of having findings that will need to be investigated,” says Matsumoto. Biopsy involves expensive equipment and complex tests, which are probably less available when it comes to public health. “If the public network offers mammography, it must also offer exams to investigate altered findings. It is necessary to follow up”, assesses the mastologist.
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This content was originally published in When should mammograms be annual? Study responds on the CNN Brasil website.
Source: CNN Brasil
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