What Is Stage 0 Breast Cancer? Onocologists Weigh In

Receiving a breast cancer diagnosis is terrifying, and it can be hard to wrap your mind around next steps. But factors like the disease stage matters. Knowing the stage of your cancer can influence the best course of treatment, as well as your overall prognosis. While most people have heard of stage 1 through stage 4 breast cancer, there is still a lot of confusion around stage 0 breast cancer.

Also known as ductal carcinoma in situ or DCIS, stage 0 breast cancer is still a form of cancer — it’s just that it’s caught very early. But what is stage 0 breast cancer, exactly, and what are the symptoms to look out for? Oncologists break it down.

What Is Stage 0 Breast Cancer?

Stage 0 breast cancer is a form of breast cancer where the cells that line the milk ducts of the breast have become cancerous, but they haven’t spread to the surrounding breast tissue, according to the American Cancer Society (ACS). About one in five breast cancers are stage 0, per the ACS.

“DCIS is a noninvasive form of breast cancer,” explains Richard J. Bleicher, MD, chief of the Division of Breast Surgery at Fox Chase Cancer Center. But while DCIS isn’t an invasive form of cancer, it can sometimes become an invasive cancer, according to ACS. Meaning, it can spread into nearby tissue and other parts of the body if it’s not treated.

What Causes Stage 0 Cancer?

It’s not entirely known what causes stage 0 cancer. “Just like with invasive breast cancer, there are a lot of modifiable and non-modifiable risk factors,” says Nina Tamirisa, MD, breast surgical oncologist at The University of Texas MD Anderson Cancer Center. She lists off these factors as potential causes:

Stage 0 Cancer Symptoms

Unfortunately, stage 0 cancer doesn’t have symptoms. “You won’t feel it, and you won’t have any symptoms anywhere in the body, including in the breast,” Dr. Tamirisa says.

That’s why the vast majority of stage 0 cancer is detected during breast cancer screening, she tells PS.

How Is Stage 0 Cancer Diagnosed?

Stage 0 cancer is usually diagnosed via mammogram. “That’s why we really emphasize that women stay on top of their screening mammograms,” Dr. Tamirisa says. In case you’re not familiar with it, a mammogram is an X-ray picture of the breast.

The U.S. Preventive Services Task Force (USPSTF) currently recommends that all women get screened for breast cancer every other year, starting at age 40 and continuing through age 74, to lower the risk of dying from breast cancer.

“Boy Meets World” alum Danielle Fishel recently made headlines after sharing that her stage 0 breast cancer was detected by mammogram. “The day I got my text message that my yearly mammogram had come up, I made the appointment,” she said on her podcast, Pod Meets World. “I hope it will encourage anyone to get in there.”

How Is Stage 0 Cancer Treated?

Treatment usually involves some form of surgery. “The current standard is to remove it surgically,” Dr. Bleicher says. That may involve breast-conserving surgery, where the cancer is removed but the overall breast is spared, or a mastectomy, where the entire breast is removed, Dr. Tamirisa says. Doctors will usually recommend one over the other based on the size of the cancer and where it’s located, she says.

If a patient has breast-conserving surgery, they’ll often have radiation afterward, Tamirisa says. “After that, depending on the biology of the DCIS, it may be recommended that patients take a pill that reduces the estrogen load in the body and helps lower the odds of it coming back,” Dr. Tamirisa says. Patients may need to take that medication for up to a decade, Dr. Bleicher adds.

That said, research into DCIS is ongoing and may influence treatment in the future. “There are ongoing trials based upon good data that suggest that we may ultimately not have to operate on some types of DCIS in the future,” Dr. Bleicher tells PS.

Ultimately, though, Dr. Bleicher says that “the prognosis for DCIS remains excellent.”

Korin Miller is a writer specializing in general wellness, health, and lifestyle trends. Her work has appeared in Women’s Health, Self, Health, Forbes, and more.