What Stage 0 Breast Cancer Means

Stage 0 breast cancer, which includes ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS), is the earliest form of breast cancer that originates in either the lobules (the glands that produce milk) or the ducts (tubes that deliver milk to the nipple) of the breast. The term “carcinoma in situ” refers to cancer that is contained within the lobule or duct where it started and has not spread to other parts of the breast or nearby lymph nodes.

Some experts do not consider DCIS and LCIS as actual “cancers” but instead classify them as precancers. When diagnosed and treated at this early stage, the expected outcome (prognosis) is usually excellent.

This article describes what stage 0 breast cancer means, including how it is treated and what to expect in terms of survival and life expectancy.

What Are the Symptoms of Stage 0 Breast Cancer?

Stage 0 breast cancer is a contained clump of abnormal cells that have not spread beyond the “basement membrane” surrounding a lobule.

Stage 0 breast cancer usually has no symptoms and is typically discovered during a routine screening mammogram or breast MRI. If symptoms are present, they may involve a lump or an abnormal nipple discharge (such as blood).

What Causes Stage O Breast Cancer?

The causes of DCIS and LCIS are still unknown. The risk factors for developing stage 0 breast cancer are similar to those for the most common form of breast cancer called invasive breast cancer.

Risk factors include:

• Being older than 50
• Having BRCA1 and BRCA2 gene mutations
• Having started menstrual periods before age 12
• Undergoing menopause after age 55
• Having dense breasts
• Having a family history of breast or ovarian cancer
• Having previously undergone chest or breast radiation therapy

How Is Stage 0 Breast Cancer Detected?

A mammogram can often detect stage 0 breast cancer during a route check-up. If the mammogram looks abnormal, a needle biopsy would be performed to extract cells to examine under a microscope. A medical specialist called a pathologist can determine if the cells are consistent with DCIS or LCIS.

The determination of stage 0 breast cancer is based on a classification system called the TNM Staging System.

The TNM Staging System classifies cancers based on the extent of the tumor (T), the involvement of lymph nodes (N), and the presence of metastasis (M). Numbers or letters after T, N, and M provide additional details.

Using the TNM system, stage 0 breast would be classified as:

• Tis: Indicating carcinoma in situ
• N0: Meaning that cancer was not found in nearby lymph nodes
• M0: Meaning that cancer has not spread to other organs (metastasized)
  

Does Stage 0 Breast Cancer Require Treatment?

Not all stage 0 breast cancers require treatment. Sometimes a watch-and-wait approach (referred to as active surveillance) is recommended to see if the cancer remains stable or progresses.

At other times, cancer treatments such as surgery, radiation, or hormone therapy may be recommended. The decision to treat or not treat is a highly personal one that requires an in-depth discussion between you and your healthcare provider.

Numerous factors need to be considered, including:

• Your age: Younger women with DCIS are at higher risk of cancer progression and recurrence, and may opt for treatment sooner.
• Your genetic risk: Having a mother, aunt, or sister with breast or ovarian cancer also increases your risk of progression and recurrence.
  
• Your pregnancy intentions: Certain cancer treatments can affect fertility. You may want to delay treatment if you intend to get pregnant or proceed after preserving your eggs for future fertilization.
• Your hormone status: Breast cancer cells with estrogen and progesterone receptors may respond to hormonal therapy. This may incentivize you to treat earlier rather than risk more impactful treatments later.

Treatment options may include:

• Lumpectomy is a surgery to remove the tumor and a small margin of normal tissue around it. This is usually followed by radiation therapy to kill any remaining cancer cells.
• Mastectomy is the surgical removal of the entire breast, used if there’s a strong family history of breast cancer or concerns about the location of the tumor.
• Hormonal therapy may follow the removal of a tumor and continue for at least five years with drugs like tamoxifen for premenopausal females or aromatase inhibitors for postmenopausal females.

Breast Cancer Healthcare Provider Discussion Guide

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How Long Is Life Expectancy With Stage 0 Breast Cancer?

The outlook for people with stage 0 breast cancer is excellent. When detected and treated at this stage, the five-year relative survival rate is 99.3%, according to the National Cancer Institute. What this means is that 99 out of 100 people diagnosed at stage 0 will live for at least five years.

Other studies suggest that 97% of people diagnosed with DCIS will survive for at least 20 years. Black females and females diagnosed with DCIS when they were under 35 are more likely to die.

After treatment for stage 0 breast cancer, there’s a small risk of recurrence or progression to invasive breast cancer. There is also a risk of new breast cancer unrelated to the first cancer (although the risk is no different than for those who have never had breast cancer).

Your healthcare provider may recommend more mammograms or breast MRIs so that any future cancers can be caught and treated early.

Summary

Stage 0 breast cancer is the earliest stage of breast cancer. Being diagnosed at this early stage sets you up for an excellent outcome. After a diagnosis of stage 0 breast cancer, different factors will be considered to determine if you need treatment or if a watch-and-wait approach is more appropriate.