Life expectancy for breast cancer is hard to determine, as it depends on the individual patient. The stage of breast cancer, treatment received and presence of metastases determine the patient's life expectancy. The life expectancy drops as the cancer becomes more advanced. Instead of specific years, the Mayo Clinic lists the five-year survival rate for each stage of breast cancer. However, patients should note that these numbers are averages and that breast cancer patients can live longer.
In stage I breast cancer, the cancerous tumor has not spread out to the lymph nodes or outside the breast. According to the Mayo Clinic, the size of the tumor is around 2 cm in diameter. The five-year survival rate of a patient diagnosed with stage I breast cancer is near 100 percent.
In stage II breast cancer, the tumor can be classified in one of three conditions: (1) the breast tumor is larger than 5 cm in diameter but has not spread to the axillary lymph nodes in the patient's underarm; (2) the tumor is less than 2 cm in diameter but has spread to three axillary lymph nodes; (3) the tumor is not in the breast but it has spread to three axillary lymph nodes. According to the Mayo Clinic, the five-year survival rate of a patient diagnosed with stage II breast cancer is between 86 and 91 percent.
Like stage II, stage III breast cancer tumors can be classified in one of three conditions: (1) the tumor is larger than 5 cm and has spread to the axillary lymph nodes, but the nodes are not attached to each other; (2) the tumor is smaller than 5 cm, but the cancer has spread to the axillary lymph nodes and the nodes are growing into each other or the surrounding tissue; (3) the tumor is smaller than 5 cm and the cancer has spread to the lymph nodes above the collarbone. According to the Mayo Clinic, the five-year survival rate of a patient diagnosed with stage III breast cancer is between 54 and 67 percent.
Stage IV breast cancer is the most advanced form of breast cancer, and it is invasive: metastases of stage IV breast cancer can appear in the lungs, liver, bone or brain. According to the Mayo Clinic, the five-year survival rate of a patient diagnosed with stage IV breast cancer is 20 percent.
The life expectancy of a breat cancer patient with brain metastases is dependent on the type of treatment received. According to the IRSA, life expectancy with an untreated brain metastasis is one month; the life expectancy increases to three to four months with radiation, and ten months when the radiation is combined with surgery.