Using Imaging Data and Genomic Data to Predict Metastasis of Breast Cancer After Treatment

Background

Breast cancer is the second leading cause of death in women around the world. According to WHO statistics, 571,000 women passed away in 2015 due to breast cancer alone. In Hong Kong, breast cancer is the most common cancer among women.

Currently, the standard protocol in breast cancer treatment consists of surgery (mastectomy), chemotherapy, radiotherapy, and possibly hormone therapy or targeted therapy depending on the presence or absence in tumor cells of certain hormone receptors such as estrogen receptors (ER), progesterone receptors (PR), or human epidermal receptor 2 (HER2). The standard protocol aims to remove the tumor and kill any remaining tumor cells. The treatment is usually adjusted based on the patients' tolerance and general health status. The standard protocol has so far been very effective in treating patients with early-stage breast cancers. The 5-year relative survival rate can be higher than 90% if patients are treated early enough. But it is still very challenging to treat patients with middle- or late-stage breast cancers, especially those with metastatic disease. For patients with metastases, the 5-year relative survival rate drops to around 20%. There are two major reasons for this drop.

While all breast cancers start from the same organ, the evolution of cancer cells shows different patterns in different patients. This is especially true when breast cancers are advanced into the middle or late stages. The standard protocol, however, is based on averaged patient statistics and does not fully account for the uniqueness of individuals. For example, patients with different genomic backgrounds respond differently to the same drug dosage and experience different side effects. Thus, population-based treatment strategies cannot provide effective, optimal treatment for every patient, especially for patients with middle- or late-stage breast cancer.

The clinical gold standard for cancer diagnosis is multi-modality imaging: mammogram and ultrasound, plus pathology of biopsied tissue. Imaging has been effective in detecting primary breast cancers but it becomes less effective for monitoring patients post-treatment because their primary tumors and affected lymph nodes have been removed. While physicians still rely on image-based screening of organs such as the lungs and liver where metastases have become established to monitor their patients post-treatment, such screening tests are not sensitive enough. Patients with greater risk of metastasis often miss the best window of opportunity for therapy adjustment before the secondary onset. When metastasis is observed in other parts of the body a few years later, often it is already too late for any effective intervention.