When a woman is diagnosed with breast cancer, the axillary lymph nodes are sometimes removed surgically or treated by radiotherapy. This is advocated because the nodes act as filters for the lymphatic drainage system but can also serve as a pathway for the spread of cancer cells to other parts of the body. One of the side effects of lymph node removal is lymphoedema, a localized swelling caused by a build-up of fluid, commonly in the patient’s arm that can also include the hand and fingers.

When planning the treatment for a patient with breast cancer, clinicians will consider the risk factors for lymphoedema and one of them is body mass index (BMI) – body mass (in kg) divided by the square of height (in m). Earlier this week, a group from Toronto published a paper in JAMA Network Open in which they developed and validated a risk model for breast cancer-related lymphoedema. Their findings suggested that mammographic breast density could be used as a prognostic factor for lymphoedema risk, to provide an estimate of fluid build-up and disease severity.

As we have highlighted recently, mammographic density not only masks breast cancer but it also serves as a significant risk factor for the disease. The BI-RADS system is a lexicon developed by the American College of Radiology that a radiologist can use to grade the mammogram: A = almost entirely fatty; B = scattered fibro-glandular tissue; C = heterogeneously dense; and D = extremely dense.

The Toronto group studied 373 patients and conducted a multi-variate regression analysis, identifying three patient factors (age, BMI and mammographic density), one cancer factor (number of cancerous lymph nodes) and one treatment factor (lymph node dissection) as independent prognostic variables. In the diagram below right (© AuntMinnie.com), the percentage of cases by breast density is plotted against severity of lymphoedema. It is clear that patients with low breast density (BI-RADS A and B) are at a greater risk of developing severe lymphoedema compared to patients with high density (BI-RADS C and D).

Maggie DiNome, a breast surgeon from Los Angeles, observed that mammographic breast density can change over the course of a patient’s lifetime and this has implications for treating women with breast cancer. She commented, “The ability to better predict the risk of lymphoedema in these patients is essential not only for appropriate counselling but also for earlier identification and intervention to mitigate the risk of developing this potentially disabling condition.”