The following groups of women should have annual mammogram screening :

a) Women who are at high risk of developing breast cancer.

b) Those who have had masectomy (removal of a breast). There is a 10% chance of cancer developing in the other breast, therefore it should be screened annually.

c) In women who have had breast conservation surgery in breast cancer . Here both breasts should be screened.

Which groups of women are at high risk of developing breast cancer?

i)White race. The normal lifetime risk in white women is 1 in 8 or 9.

ii) Older age group (>40 years).

iii) Family history of breast cancer in mother,sister or daughter (especially if it is bilateral or pre-menopausal).

iv) BRCA1 or BRCA2 gene mutation.

v) Previous history of endometrial cancer, cancer in the other breast and history of proliferative forms of fibrocystic disease.

vi) Early menarche (under age 12).

vii) Late menopause (after age 50).

viii) Nulliparous or late first pregnancy.

The use of mammography in detecting breast cancer:

Mammography is the best technique used for the early detection of early breast cancer.

With screening for breast cancer the overall mortality from breast cancers is reduced by 20 to 30% in those between 50 to 69 years of age . This has been confirmed by numerous clinical trials. The reduction in overall mortality is attributed to the widespread use of tamoxifen.

In communities/countries where mammography is used for screening of breast cancer, screening is done every 1 or 2 years for women who are in the age group 40 to 59.

It is also estimated that 1 in 200 women screened for breast cancer over a period of 15 years is saved from premature death.

The type of mammography used presently is called the “film screen mammography”. This deliveres a very low dose of radiation (less than 0.4 cGy) to the central part of the breast. The film screen mammography has replaced the xeromammographic technique because of the low radiation exposure in the film screen mammography technique.

Mammography can detect breast cancers even before a mass can be palpated, in fact slowly growing cancers can be identified by mammography 2 years before reaching a size that can be palpated during physical examination by a doctor.

Impalpable cancers such as cancer-in-situ (carcinoma-in-situ) and subclinical invasive cancers can be detected. Up to 80% of  breast cancers detected by  mammographic screening have not spread to the axillary lymph nodes.

What is the appearance of breast cancer on mammography?

The usual features of breast cancer on mammography are stellate or irregular densities, disturbance of breast architecture or microcalcification (>2 mm). The microcalcification may be clustered, punctuate, microlinear or branching and concentrated in an area >1 cm in diameter

The most easily recognizable abnormality on mammography is calcification. Polymorphic microcalcifications are commonly associated with carcinoma of the breast. These calcifications are usually five to eight in number. They are also usually aggregated in one part of the breast. The aggregates may also form Y or V shaped configurations.

What are the disadvantages of mammography?

i) 10 to 15% of cancers are not detected by mammography , in fact cancer may occur in between screening (known as interval carcinoma). Due to the minimal calcification lobular carcinoma of the breast is difficult to detect.

ii) False negatives- A negative mammogram may give a false sense of reassurance as a tumor may still exist.

iii) False positives- There are up to 5 to 10 false positives on mammography for each case of cancer diagnosed by biopsy after screening.

iv) To interpret a mammogram a radiologist with good experience must be present.

v) The equipment used for mammography is expensive and not affordable by most developing countries. Trained staff are also needed to operate the equipment.

vi) Exposure to radiation- exposure to radiation from repeated mammograms may also raise the risk of  radiation induced breast cancer.

What are the indications of mammography?

i) To screen regularly women at risk of developing breast cancer.

ii) To evaluate each breast when a diagnosis of potentially curable cancer of the breast has been made.

iii) To look for occult cancer of the breast when there is a metastatic disease of the axilliary lymph nodes (unknown primary cancer).

iv) Evaluation of an ill defined breast mass.

v) To screen women prior to cosmetic surgery.

vi) Follow up of women with breast cancer that has been treated with surgery (Breast conserving urgery) and radiation.

It must be emphasized that mammography is not a substitute for biopsy because it cannot reveal the diagnosis. The changes seen in the mammogram in cancer of the breast can also occur in benign breast diseases.

Imaging techniques for screening of breast cancer ,other than mammography

Magnetic resonance imaging, ultrasound and PET (positron emission tomography) are been studied as screening tools for breast cancer.

References:

Page 473. Detection of breast cancer. Chapter 28. The Breast.Principles and practice of surgery including pathology in the tropics. 3rd Edition by E.A. Badoe, E.Q. Archampong and J.T. da Rocha-Afodu.

Page 290, Chapter 6. Epidemiology of Chronic Non- communicable Diseases and Conditions. Park’s Textbook of Preventive and Social Medicine by K. Park. 17th Edition.

Pages 707 to 709, Early Detection of Breast Cancer. Chapter 16 Breast. Current Medical Diagnosis and Treatment 2006.Edited by Lawrence M. Tierney,Jr. Stephen J. McPhee Maxine A. Papadakis.

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