Doctors use staging to identify how far a cancer has spread in a person. Staging cancer also gives information about how quickly it is growing and how dangerous it might be.
Stage zero—or stage 0—breast cancer, which is also called carcinoma in situ, is the earliest form of breast cancer. Most people with stage zero breast cancer survive, as it has not spread anywhere else.
- Because stage zero breast cancer is small and noninvasive, it can also be difficult to detect.
- Stage zero breast cancer is not a type of cancer, but a grading of how far the cancer has spread.
- Breast cancer treatment can be painful, costly, and stressful. For most women, it makes sense to treat stage zero breast cancer despite the risks.
What is stage zero breast cancer?
Stage zero breast cancer rarely has any symptoms, and will not have spread to other parts of the body. This makes it difficult to identify.
The stage of breast cancer provides key information about how invasive it is, and whether it has spread or is likely to spread to other areas of the body.
Stage zero breast cancer or stage 0 is noninvasive. That means it has not spread to other cells in the breast or to other organs. Some doctors refer to stage zero breast cancer as precancer.
In most cases, it is discovered by accident, such as after a biopsy or during a breast-imaging test to view another lump. Stage zero breast cancer does not usually cause lumps or other symptoms.
Although stage zero breast cancer is small and has not spread, it may require treatment to prevent it from spreading to other areas of the body in the future.
The right treatment depends on which type of stage zero breast cancer a woman has. With treatment, more than 9 in 10 women with stage zero breast cancer survive 5 years or longer.
There are two types of stage zero breast cancer, both of which are described below:
Lobular carcinoma is cancer of the glands that make breast milk, which are called the lobes or lobules.
Lobular carcinoma in situ is a form of lobular cancer that does not normally spread. It is, however, a risk factor for other forms of breast cancer. About a quarter of women with lobular carcinoma eventually develop another type of breast cancer.
For this reason, a lobular carcinoma in situ diagnosis may mean a woman will need more frequent breast cancer screenings in the future.
Ductal carcinoma in situ (DCIS) is breast cancer of the milk ducts. The milk ducts in the breast tissues are canals that allow milk to move from the milk glands to the nipple.
Left untreated, ductal carcinoma can spread and become more aggressive. In about half of cases, ductal carcinoma will become a more aggressive cancer.
Doctors cannot predict which cases of ductal carcinoma will become more aggressive ones. Low-grade tumors or those with well-defined borders and that grow slowly may be less likely to spread, however.
Other stages of breast cancer
MRI scans or mammograms may be used to diagnose breast cancer, and determine the stage of the cancer.
Staging progresses from 0 to 4 with higher numbers indicating more advanced cancers. To determine the stage of breast cancer, doctors look at three factors:
- The size of the breast tumor, which is usually abbreviated as T.
- Whether the cancer has spread to lymph nodes and how many are affected. This is abbreviated as N.
- Whether the cancer has spread to other areas of the body, called metastasis. This is abbreviated as M.
There are four stages of breast cancer after stage zero:
- Stage 1: Cancers involve smaller tumors that have spread very little if at all.
- Stage 2: These are slightly larger, and have spread to nearby tissue, but not to other organs. They may infect a small number of lymph nodes or a limited bit of nearby tissue.
- Stage 3: These cancers are larger, and have spread further than stage 2 tumors. They may infect breast tissue or nearby lymph nodes but not other organs.
- Stage 4: These tumors are the largest and most life-threatening. They may have spread to nearby or distant lymph nodes, or to other organs.
Doctors may further divide stages into A and B. Those cancers classified as B are more invasive than A, so stage 1B breast cancer has spread further or is larger than stage 1A.
Will it spread?
A breast cancer that is diagnosed as a lobular carcinoma will not typically spread to other areas. However, because it is a risk factor for other breast cancers, it requires more careful monitoring.
A breast cancer that is a ductal carcinoma can spread, but there is no way to accurately predict whether a given case of this form of cancer will spread.
Radiation therapy may be recommended for stage zero breast cancer. Some argue that invasive treatments are uneccesary for this form of cancer, while others argue that not treating the cancer at all is a risk.
In recent years, treatment of this noninvasive form of breast cancer has been the source of some controversy.
Because DCIS does not cause symptoms and neither does it always spread, some women are frustrated by the treatment they feel was unnecessary or harmful.
A 2015 study added to criticism of DCIS treatment when it found no difference in survival rates between women who were treated and women who were not. However, doctors who support early treatment counter this argument by pointing to data showing there is no way to predict whether or not DCIS will become invasive.
Treatment needs to take into account the person's history, treatment needs and goals, and other breast cancer risk factors they may or may not have.
Treatment options include:
- breast surgery
- radiation therapy
- hormonal therapy
Monitoring may also be recommended for women with a history of stage zero breast cancer. This is because they may need ongoing care for other kinds of cancer.
Stage zero breast cancer may be worrisome, but it is almost always survivable. Treatment can save lives, particularly when there is a risk of the cancer returning or spreading.
Women who are unsure whether they should seek treatment should consult a doctor they trust and consider seeking a second opinion if they are still uncertain.