Breast cancer is the most common cancer among women worldwide as well as in India. According to a study published in Online First by The Lancet, breast, cervical and stomach cancers are responsible for majority of the cancer deaths among women in India. The incidence of breast cancer is rising in India over the last few decades.
The purpose of screening mammography is to detect cancer in the early stages. Advances in the treatment of cancer have considerably improved the cure rates; however, a major factor that determines prognosis is the stage of cancer. Response to treatment and prognosis is better when the cancer is diagnosed in the early stage. Screening mammography and other imaging techniques like breast ultrasound and breast MRI can help to detect small tumours at an early stage that cannot be felt by manual palpation, and before they can spread.
American Cancer Society Recommendations for Screening Mammography (2015)
A. Women of age 40 to 49 years
Women aged 40 to 44 years should have the choiceto start annual breast cancer screening with mammograms if they wish to do so. The risks of screening, as well as the potential benefits, should be considered. Women aged 45 to 49 years should get mammograms every year.
B. Women of age 50 to 74 years
Women aged 50 to 54 years should get mammograms every year. Women aged 55 years and older should switch to mammograms every 2 years, or have the choice to continue yearly screening.
C. Women of age 75 years and above
Screening should continue as long as a woman is in good health and is expected to live 10 more years or longer.
D. Women with dense breasts
There is not enough evidence to make a recommendation for or against yearly MRI screening.
E. Women at high risk for breast cancer
Women who are at high risk for breast cancer based on certain factors (such as having a parent, sibling, or child with a BRCA 1 or BRCA 2 gene mutation) should get an MRI and a mammogram every year.
Types of X-Ray Mammography
It is done in asymptomatic population with the intention to detect breast cancer at an early stage so that maximum cure rate and life expectancy can be achieved. Mammography screening is effective in helping to reduce breast cancer mortality in women over the age of 40.
It is performed on asymptomatic patient to evaluate further an abnormality detected earlier in screening mammography. The idea is to identify and classify the abnormality into benign or malignant disease. Benign abnormality has relatively better prognosis. Breast cancer has variable outcome based on the extent of spread of cancer.
Views for X-Ray Mammography
Adequate craniocaudal view (CC)
• All glandular tissue identified.
• Nipple in profile.
• Nipple in midline of image.
• Length of posterior nipple line within one 1cm in size c.f. PNL on MLO.
• Images symmetric.
Adequate mediolateral oblique view (MLO)
• Pectoral shadow is seen down to level of nipple or lower.
• Inframammary fold well seen.
• Nipple in profile.
• Length of posterior nipple line within one 1cm in size c.f. PNL on CC.
– Images symmetric.
Addition of Breast Ultrasound (Sonomammography) is a Boon
Many of the younger women have dense breasts wherein the sensitivity of mammography may be suboptimal. In Asia, where women characteristically have dense breast tissue, age-specific breast cancer incidence peaks in the younger age group of 40 to 49, compared with women 60 to 70 years old in Western countries.
Addition of ultrasound to mammography provides increased sensitivity in detecting cancers, some of which are small invasive cancers, leading to a reduction in breast cancer mortality.
Women with dense breasts can be 6 times more likely to develop cancer. Adding ultrasound to annual mammograms improves breast cancer detection in women with dense breasts. Some studies found that theinterval cancer rate was higher in women not randomised to receive ultrasound for breast examination. Ultrasound is particularly good at finding small breast cancers that haven’t spread to the lymph nodes yet.
But mammograms are still needed because ultrasound alone doesn’t detect all types of breast cancers.
Advantages of breast ultrasound:
Low-cost screening modality which is easily available.
No risk of radiation hazards hence can be repeated for frequent monitoring of targeted abnormality.
Screening of dense breasts where x-ray mammogram have limitations.
Good tool for image-guided breast biopsy of suspicious abnormality.
Hence the combination of x-ray mammography and ultrasound of breast is recommended for routine screening and diagnostic mammography evaluation.
Role of MRI in Breast Imaging
To detect and get more information about indeterminate breast lesions on both x-ray mammography as well as breast ultrasound.
Screening of dense breasts.
No concern for radiation exposure. Hence screening of breasts in women of younger age group who have family history of breast cancer and/or positive for genes predisposing for breast cancer.
To detect additional micrometastatic lesions in an established case of breast cancer. These may not be detected on x-ray mammography. It helps in better treatment planning and correctly understanding the disease prognosis.
Scanning Technique of Breast MRI
A dedicated bilateral breast coil is mandatory.
The spatial and temporal resolution must be sufficient.
– T-1 weighted non-fat suppressed and fat-suppressed.
–T-2 weighted fat suppressed.
– Dynamic post contrast fat suppressed T1-weighted.
Limitation of breast MRI
It is not easily available everywhere, especially in developing and underdeveloped countries.
It is costly.
Breast MRI interpretation needs dedicated radiologists.
Dedicated breast coilis required for scanning breasts.
X-ray mammography is a timetested low-cost modality to pick up breast cancer at a stage where it has maximum curative potential and less mortality rate. Use of Ultrasound for women of younger age group adds to sensitivity in detection of early breast cancers. Ultrasound is also the first screening modality for imaging benign breast disease. Breast MRI is especially good for detecting indeterminate lesions on other imaging techniques and avoids radiation concerns in screening younger population.