The researchers documented 16,059 cases of breast cancer between 1991 and 2020. They compared the course of the disease in women who showed up for their first scheduled mammogram with those who missed it. The risk of a stage 3 diagnosis was 53% higher in the group that delayed the first investigation, and for stage 4 the difference reached 260%.
Women who miss their first mammogram have a 40% higher risk of dying from breast cancer. The data comes from a large study that included 430,000 female participants in Sweden, followed for nearly 30 years.
“Women who did not participate in the first screening were more likely to miss future screenings as well. This delay in diagnosis may contribute to the more advanced stage of cancer at the time of detection and higher mortality,” pointed out Dr. Jean Bao, a surgical oncologist at Stanford University School of Medicine in the US.
Cancer incidence was similar in both groups
The researchers found that among women who had their first mammogram, 7.8 percent were diagnosed with cancer, compared with 7.6 percent of those who delayed the test. The main difference was the stage of the disease detected.
“Mammography screening allows cancer to be identified when the tumor is smaller and easier to treat. When investigations are delayed or missed, the disease can progress to larger sizes,” explained Dr. Jean Bao.
The study also showed that women who missed their first mammogram continued to delay follow-up screenings, and the diagnosis was established at more advanced stages, when treatment options are more limited and the prognosis more reserved.
How often should mammograms be done?
A systematic review conducted by Carlos Canelo-Aybar and his team and published in the British Journal of Cancer in 2022 compared the effectiveness of annual, two-year and three-year mammograms in women at average risk of breast cancer.
For the 50–69 age group, the conclusion was that screening every two years offered the best balance of benefits and risks. Annual mammograms may detect some cancers somewhat earlier, but they increase the likelihood of false positives, which would require unnecessary investigations and biopsies, with additional costs and anxiety for patients.
Figures from US breast cancer surveillance registries confirm that for women in this age group, the risk of a false-positive result over the next 10 years is 55.2% at annual screening, 35.4% at two years, and 24.8% at three years.
For women ages 45 to 49, the additional benefits of annual mammograms are modest compared to the adverse effects. Statistical models showed that, per 100,000 women, annual screening prevents 30 more deaths than biennial screening, but also causes 14 cases of radiation-induced cancer, two of which are fatal.
For women between 70 and 74 years of age, the differences between screening intervals are minimal. According to estimates, in 100,000 women, 100 deaths can be avoided by annual screening, 90 by biennial screening and 80 by triennial screening.
The only study with moderate-certainty evidence
Between 1989 and 1996, British researchers ran the UKCCCR, a large randomized trial involving 99,389 women aged 50 to 62. The participants were randomly divided: some had mammograms annually, and others every three years.
After nearly 14 years of follow-up, annual screening was associated with an 11% lower risk of breast cancer death (hazard ratio 0.89, 95% confidence interval 0.73 to 1.07). In the group monitored annually, 25 percent of the tumors found were 10 millimeters or larger, compared with 19 percent in the group screened every three years, a difference that points to earlier detection of the disease.
This was the only study in the systematic review published in 2022 that was rated with a moderate level of certainty, the rest of the included studies were rated “very low certainty,” due to methodological limitations and wide variation between results.
Radiation emitted during mammography, real risk or myth?
Mammography uses a small amount of ionizing radiation. The average dose is about 0.4 mSv, equivalent to natural radiation exposure over several months. Even if exposure is repeated over time, the overall level remains small compared to the benefits of early breast cancer detection.
Modeling analyzes showed that among 100,000 women ages 50 to 74, screening every two years could lead to about 27 breast cancer cases attributed to radiation, compared with 49 if screening is done annually.
Estimates of radiation-related deaths are very low: four for biennial screening and seven for annual screening. At the same time, the benefits clearly outweigh the risk, considering that, in the same scenario, screening every two years would prevent more than 520 breast cancer deaths, and the annual one around 690.
In addition, technology has evolved and current doses are lower than those used in the past. Digital mammography and tomosynthesis (3D mammography) can improve the visibility of dense breast tissue and decrease the number of additional investigations without increases in radiation.
The problem of overdiagnosis
Overdiagnosis refers to the identification of cancers that would never have caused symptoms or health problems. Modeling analyzes estimate that for 100,000 women aged 50 to 74, annual screening could lead to about 2,900 such cases, compared with 2,000 for screening every two years and 1,600 for screening every three years.
For example, the British Age Trial research found a similar incidence of invasive cancers in women who had a single mammogram after age 50 and those who had annual mammograms between ages 40 and 49, followed by three-year follow-ups.
The authors of the analysis published in the British Journal of Cancer noted that there is no single method of measuring overdiagnosis. Many models include different assumptions, such as the clinical relevance of ductal carcinoma in situ (DCIS) and the possibility that some tumors regress spontaneously without requiring treatment.
Specialists' recommendations
The World Health Organization recommends organized screening programs for women between 50 and 69 years, the range with the highest incidence of the disease. The American Cancer Society recommends annual screenings between ages 45 and 54, then biennial screenings from age 55. The British program indicates screening every three years for the 50-70 age group.
Romanian specialists recommend annual breast ultrasound and mammography two years after the age of 40, when the breast tissue changes its structure and becomes more fibrous. This change is related to aging and, where appropriate, breastfeeding.
The doctor may request an ultrasound every six months depending on the results of the investigation. Mammography can also be proposed before the age of 40 if there is a family history or other risk factors.
Mammography with tomosynthesis offers three-dimensional images and allows more precise identification of anomalies compared to classic mammography, being considered the most advanced method of radiological assessment of breast tissue currently available.
Free screening in Romania
The Ministry of Health recently announced that prevention services are available free of charge to all Romanians, regardless of insurance status. Any woman can go to the family doctor for preventive consultations and receive a referral for a free mammogram.
“Medical prevention is becoming a national priority again. Free access to medical checks, analyses, investigations and monitoring, including for uninsured people, is only the first step. Now we have to work on changing mentalities and forming healthy habits. Recurrent health checks, even when it doesn't hurt, save lives, time and resources. Go to the doctor regularly, with confidence,” said Dr. Alexandru Rogobete, Minister of Health.
Women aged 18 to 39 receive a free consultation annually for risk assessment and advice on smoking, diet, physical activity and weight. Those over 40 can benefit from up to three free consultations per year for assessment, advice and monitoring.
The national program targets the 50-69 age group, according to WHO recommendations, but the information campaign encourages all women over 40 to talk to their doctor about individual risk factors.
