Women with diabetes more likely to be diagnosed with advanced stage breast cancer

Diabetes is associated with more advanced stage breast cancer, according to a new study by the Institute for Clinical Evaluative Sciences (ICES) and Women's College Hospital.

The findings, published today in the journal Breast Cancer Research and Treatment, confirm a strong link between diabetes and later stage breast cancer at diagnosis for Canadian women.

"Our findings suggest that women with diabetes may be predisposed to more advanced stage breast cancer, which may be a contributor to their higher cancer mortality," said Dr. Lorraine Lipscombe, a scientist at ICES and Women's College Research Institute.

In the study, Dr. Lipscombe examined stage at diagnosis among women aged 20-105 years who were newly diagnosed with invasive breast cancer between 2007 and 2012.

From an analysis of more than 38,000 women with breast cancer, 6,115 (15.9 per cent) of the women had diabetes. Breast cancer patients with diabetes were significantly more likely to present with advanced stage breast cancer than those without diabetes. Women with diabetes were 14 per cent more likely to present with Stage II breast cancer, 21 per cent more likely to present with Stage III breast cancer, and 16 per cent more likely to present with Stage IV than to present with Stage I. The results also show lower mammogram rates in women with diabetes, which could account for later stage disease. Women with diabetes also had a higher risk of lymph node metastases (spreading of the cancer) and larger tumors than women without diabetes.

Breast cancer often begins in the breast ducts as ductal carcinoma in situ (DCIS). Once out of the breast, cancer often spreads first to the axillary (underarm) lymph nodes. One or more of the lymph nodes are usually removed during breast surgery to determine whether the nodes are involved. (See the axillary node dissection and sentinel node biopsy sections for more information on how lymph nodes are removed). In some cases, breast cancer may spread to other regions of the body without involving the axillary lymph nodes. If the cancerous tumor is located in the medial portion of the breast (near the nipple), it may spread to the internal mammary nodes which are located between the ribs and beneath the sternum. In some cases, cancer may spread through the bloodstream without being detected in the lymphatic system.

In 10% of breast cancer diagnoses, the cancer has already spread to distant organs in the body. A primary diagnosis of Stage IV breast cancer may indicate a rapid progression of the disease or that the cancer was present but not detected in the breast for some time. To help detect breast cancer in its earlier stages when it is most curable, women should follow the guidelines for early detection established by the American Cancer Society which include monthly breast self-examinations, annual clinical breast exams, and annual mammography (the latter beginning at age 40).

Metastatic breast cancer may also occur from a recurrence (return) of breast cancer after initial treatment. There are three types of breast cancer recurrences: local, regional, and distant. Local and regional recurrences are usually less serious than distant recurrences and may be detected by mammogram or seen as abnormalities with breast imaging exams (such as ultrasound or T-scan).