Chapter1 Motivation

According to World Health Organization\(*\), Cancer is a leading cause of death worldwide, accounting for an estimated 9.6 million deaths in 2018. And amongst all cancer types, breast cancer(along with lung cancer) has the top cases of death: 2.09 million cases in 2018. According to the CDC\(*\), Breast cancer is also the second most common cancer among women in the United States, comprising 22.9% of invasive cancers in women and 16% of all female cancers. However, because of the cancer’s characteristics, breast cancer patients have relatively high 5-year survival rate of 85% compared to other more lethal cancers according to research conducted in the UK\(*\). We think it is worthwhile to look at the relationship between survival/recurrence time and some diagnostic criterion of breast cancer. We are also going to explore the effect of different treatments on survival/recurrence.

1.1 Some Background Information

For doctors to be able to assess the severity and different types of breast cancer, researchers have come up with a diagnosing system called the TNM\(*\) Staging system that is widely used in the diagnostics of breast cancer:

Tumor(T): How large is the primary tumor in the breast?

Node (N): Has the tumor spread to the lymph nodes? If so, where, what size, and how many?

Metastasis (M): Has the cancer spread to other parts of the body?

Generally, the results from the above three features are combined to form a diagnosis of a total of 5 stages of breast cancer: stage 0 (zero), which is non-invasive ductal carcinoma in situ (DCIS), and stages I through IV (1 through 4), which are used for invasive breast cancer.

In addition, cancer cells are given a grade when they are removed from the breast and checked in the lab. Based on how much they look like normal cells, there are three grades of cancer cells:

Grade 1 / well differentiated: The cells are slower-growing, and look more like normal breast tissue, meaning that cancer is less likely to spread.

Grade 2 / moderately differentiated. The cells are growing at a speed of and look like cells somewhere between grades 1 and 3.

Grade 3 / poorly differentiated: The cells look very different from normal cells, meaning a faster-growing cancer that’s more likely to spread.

We will use data related to information above to conduct our exploration.