Ductal carcinoma in situ (DCIS) is a non-invasive form of breast cancer, also referred to as stage 0. The term “in situ” signifies that the abnormal cells are confined to their original location inside the milk ducts of the breast. Because these cells have not spread into the surrounding breast tissue, DCIS is associated with a favorable prognosis.
Examining the 20-Year Mortality Data
When reviewing long-term survival after a DCIS diagnosis, it is important to distinguish between different mortality metrics. One is breast cancer-specific mortality, which tracks deaths directly caused by breast cancer. Large-scale studies have found that the 20-year mortality rate from breast cancer after a DCIS diagnosis is approximately 3.3%.
A second metric is all-cause mortality, which includes deaths from any cause, such as heart disease or other cancers. Over a 20-year period, this rate will naturally be higher than the breast cancer-specific rate. One study noted that while DCIS was associated with a higher risk of dying from breast cancer, it was not linked to an increase in deaths from other causes.
This distinction is important for placing the risk into context. While a DCIS diagnosis does slightly increase the long-term risk of breast cancer mortality compared to the general population, the absolute risk remains low.
Risk of Recurrence and Progression to Invasive Cancer
The main concern with DCIS is its potential to recur, particularly as an invasive form of breast cancer. A recurrence means the cancer has returned after initial treatment and may reappear in the same breast as either DCIS or invasive ductal carcinoma (IDC).
If DCIS recurs as IDC, the cancer cells are no longer confined to the milk duct and have breached the ductal wall to grow into the surrounding breast tissue. This gives the cancer the ability to spread to lymph nodes and other parts of the body, a process called metastasis. Distant metastasis is the primary mechanism through which breast cancer can become life-threatening.
Studies show that the risk of dying from breast cancer increases significantly if a patient with a history of DCIS later develops an invasive cancer in the same breast. Preventing its recurrence as an invasive cancer is the principal goal of treatment.
Key Factors That Influence Long-Term Outcomes
Several factors related to the patient, the tumor, and chosen treatments can influence the long-term prognosis after a DCIS diagnosis.
Patient characteristics play a role in survival rates. Age at diagnosis is a factor; studies have shown that women diagnosed before the age of 35 have a higher 20-year breast cancer-specific mortality rate compared to older women (7.8% vs 3.2%). Research has also identified that Black women experience a higher risk of death from breast cancer following a DCIS diagnosis compared to non-Hispanic white women.
The biological features of the DCIS lesion are also predictive. Tumor grade, which describes how abnormal the cancer cells appear, is an indicator. High-grade DCIS cells are more disorganized and grow more quickly than low-grade cells, which is associated with a higher risk of recurrence. Hormone receptor status also affects prognosis and treatment options.
A lumpectomy, or breast-conserving surgery, removes the DCIS lesion and a small margin of healthy tissue and is often followed by radiation therapy to lower the risk of recurrence. Another surgical option is a mastectomy, the removal of the entire breast. For hormone receptor-positive DCIS, endocrine therapy may be recommended to block hormones that could fuel cancer cell growth.