When the doctor says you have stage 0 breast cancer, and now you have lots of questions. What does that mean? Is it even really cancer?

Stage 0 cancers are basically pre-cancerous lesions and are also called “carcinoma in situ.”
Carcinoma means cancer and “in situ” means “in the original place.” (i.e. the cancer confined to its original place which is the earliest non- invasive stage of breast cancer)

The five-year survival rate for stage 0 breast cancer is 93-95 percent. This means that almost all women diagnosed with stage 0 disease will live for at least five years after being diagnosed.

 In fact, women diagnosed with stage 0 breast cancer usually live long and healthy lives.

Stage 0 breast cancer is difficult to detect. There’s no known cause, and most people don’t have any symptoms, though you may notice a lump or bloody discharge from your nipple.

 However, breast self-exams and routine screening are always important and can often lead to early diagnosis, when the cancer is most treatable.

Stage 0 disease is most often found by accident during a breast biopsy for another reason, such as to investigate an unrelated breast lump.

Types of stage 0 breast cancer

Three possible types of “in situ carcinoma” of the breast tissue are:

1. Stage 0 ductal carcinoma in situ (DCIS) is a non-invasive cancer where abnormal cells have been found in the lining of the breast milk duct. Ductal Carcinoma in Situ is very early cancer that is highly treatable, but if it’s left untreated or undetected, in about 50 percent of the cases, it can spread into the surrounding breast tissue. Today, stage 0 DCIS is being diagnosed more often because more women are having routine mammogram screenings.
2. Stage 0 Lobular carcinoma in situ (LCIS) occurs when abnormal cells develop in the lobules. These cells are not cancerous and this condition rarely becomes invasive cancer. However, women who develop LCIS may be at increased risk for developing breast cancer in the future. For women who develop LCIS, the risk of getting an invasive cancer is 20 - 25 percent over 15 years after the initial diagnosis. Patients who have been diagnosed with LCIS,  are recommended to have regular clinical breast exams and mammograms. Hormone therapy medication (Tamoxifen) helps prevent cancer cells from growing.
3. Paget’s disease: Carcinoma in-situ arising from the nipple ducts.

Even though Stage 0 breast cancer is considered “non-invasive,” it does require immediate treatment, typically surgery or radiation, or a combination of the two.  Chemotherapy is usually not part of the treatment regimen for earlier stages of cancer but hormonal therapy is a part of the treatment.

Treatment needs to consider the person's history, treatment needs and goals, and other breast cancer risk factors they may or may not have.

Surgery is the main treatment for DCIS. Most women are offered breast-conserving surgery. If there are several areas of DCIS in the breast, doctors may do a mastectomy to make sure that all of the cancer is removed.

 Lymph nodes under the arm (called axillary lymph node dissection) are usually not removed for DCIS because this cancer has not spread outside the duct in the breast.

To lower their risk of developing invasive breast cancer, some women with DCIS/LCIS may choose to have their breasts removed (called a prophylactic mastectomy). (If genetic tests BRCA1&2 positive)

External beam radiation therapy is usually given after breast-conserving surgery for DCIS. It is used to lower the risk that cancer will come back (recur) in the breast, especially if there is high-grade DCIS. LCIS is not treated with radiation therapy.

Hormonal therapy (Tamoxifen) is offered for hormone receptor–positive DCIS. Hormonal therapy is started as soon as the cancer is diagnosed. It is given for up to 10 years to lower the risk that you will develop another breast cancer.

Women with LCIS may be offered tamoxifen to lower the risk that an invasive breast cancer will develop.