What To Know About Ductal Carcinoma In Situ (DCIS)—Stage 0 Breast Cancer

Ductal carcinoma in situ (DCIS)—or stage 0 breast cancer—is considered a non-invasive or pre-invasive cancer diagnosis. The condition needs to be treated, however, to ensure that it doesn't turn into invasive breast cancer. Here's what you need to know about prognosis, treatment, and research concerning stage 0 breast cancer.

"It still comes with risks, so it should still be respected," Marleen Meyers, MD, medical oncologist and director of the Perlmutter Cancer Center Survivorship Program at NYU Langone Health, told Health.

DCIS Affects Cells in the Milk Ducts

Each breast has milk ducts, which act as a canal system to transport milk to nursing babies. DCIS occurs when cells in one of those ducts have mutated and multiplied to look like cancer cells.

About one in five newly diagnosed breast cancers is DCIS. Because those cells usually stay confined to the duct and do not spread to surrounding tissue, DCIS is also known as stage 0 breast cancer.

Usually Found on a Mammogram

For most, DCIS is picked up on routine mammograms. "Typically, the mammogram finds a calcification—a small cluster of cells with abnormal shapes and sizes—and then it is diagnosed after a biopsy," said Dr. Meyers.

Occasionally, though, DCIS grows large enough that it forms a noticeable lump. Some people with DCIS may also have unusual nipple discharge or a condition called Paget's disease that causes the skin around the nipple to become thick and dry.

Increase in Stage 0 Diagnosis

"We've seen a huge increase in the number of DCIS cases diagnosed in the last 20 years," Julia White, MD, director of breast radiation oncology at the Ohio State University Comprehensive Cancer Center, told Health.

In the 1990s, only about 15,000 to 18,000 DCIS cases were diagnosed per year, Dr. White said. That number has grown to more than over 51,000.

"That's because so many women are now getting mammograms, and the technology is so good, that we pick up very small lesions," explained Dr. White.

As a result, people are getting treated earlier than ever, which means there are fewer chances for DCIS to break out of the milk duct and become invasive. However, there's no way to tell which lesions will become invasive and which ones will not.

Prognosis Is Excellent

Because DCIS is noninvasive, patients' chances of recovery and long-term survival after treatment are great. A 2019 study found that, after 10 years of follow-up, the survival rate was approximately 98%.

Additionally, the prognosis was also "extremely good" for people whose DCIS diagnosis was managed with approaches such as:

• Surgical excision
• Radiotherapy
• Endocrine therapy

After DCIS, the Risk of Another Cancer Is Higher

Stage 0 breast cancer still comes with risks. "When you have DCIS, it means your risk of developing another DCIS or an invasive breast cancer is higher than the general population," said Dr. Meyers.

Researchers conducted a study about breast cancer, comparing women in the general population to women diagnosed with DCIS. Those diagnosed with DCIS were more at long-term risk for invasive breast cancer, as well as death due to breast cancer, within 20 years of detecting DCIS during a breast cancer screening.

"Whatever caused the cells to mutate will generally occur in more than one duct—and sometimes, those mutated cells can break through a duct and become invasive breast cancer," added Dr. Meyers.

But why that happens isn't clear. "We don't know why some [cases of] DCIS have the ability to do this while others don't, so right now we want to treat all of them with at least surgery, and maybe more," said Dr. Meyers.

Tumor Size Matters

After a person is diagnosed with DCIS and has the abnormal growth removed via surgery, the next step is to assess the risk of a more invasive cancer returning.

One important factor in that calculation is the size of the DCIS, said Dr. White—large DCIS areas are considered to be those that are around 2 to 2.5 centimeters (or 20 to 25 millimeters) and greater.

"With DCIS lesions [bigger] than 20 to 25 millimeters, the general recommendation is for more than just surgery," explained Dr. White. Additional treatment may include radiation and hormone therapy.

However, DCIS areas that are smaller than 2.5 centimeters are considered to be a low-risk feature of the condition.

"Nuclear Grade" of DCIS Matters Too

Healthcare providers will also consider the nuclear grade of DCIS, which is determined by looking closely at the nuclei of the cells removed during a biopsy. There are three grades of DCIS:

• Low, or grade 1—which looks the most like normal, healthy cells
• Intermediate, or grade 2
• High, or grade 3—which looks the most abnormal and grows the fastest

High-grade DCIS is sometimes described as "comedo" or "comedonecrosis," which means that dead cells have built up inside the fast-growing tumor. The higher the grade, the greater chance a person has of also having invasive breast cancer, either with the DCIS or at some point in the future.

DCIS Can Be Removed With Surgery

DCIS can often be removed via a lumpectomy, which is a surgery that spares the surrounding breast tissue.

When performing a lumpectomy, surgeons aim to remove all of the cancerous cells, plus a 2-millimeter margin of healthy cells around the tumor. This helps ensure that the cancer is 100% removed and lowers the risk of a recurrence.

In some cases, if DCIS has infiltrated multiple ducts or a tumor has grown large enough, removing the entire breast via mastectomy may be recommended.

Also, because some DCIS may never progress, some patients may also opt to skip surgery, adopting a watch-and-wait approach instead.

Some People Get Radiation

Healthcare providers and patients should decide together whether further treatment is needed to reduce the risk of another DCIS or invasive cancer, including medications or radiation. This can be determined through genomic testing or by looking at factors like the patient's age, family history, and tumor size and grade.

"Several years ago, radiation would have been given to everyone who had DCIS, period," said Dr. Meyers. "But now, it's a little more tailored to the type of DCIS and the type of patient, and there's been a downward trend of getting less radiation or avoiding it completely, if possible."

In general, radiation is typically part of treatment after breast-conserving surgery (BCS). However, radiation does come with side effects—and it has not been shown to extend survival in patients with DCIS. Instead, it's only been shown to reduce the risk of another cancer occurring.

Therefore, patients should weigh the pros and cons carefully, added Dr. Meyers, and make the best individual decision for them.

Hormone-Blocking Medicines

For some people with DCIS, taking drugs that block the production of sex hormones—like tamoxifen or aromatase inhibitors—can also reduce the risk of a DCIS recurrence or a future invasive cancer. But these medicines also cause side effects, and they won't lower the risk for everyone.

To tell if these drugs will be effective, a DCIS tumor should be tested to see if it has estrogen and progesterone receptors. "The majority of women will have positive hormone receptors," said Dr. Meyers. "But for those who don't, we don't do risk reduction with these drugs because they're not likely to be advantageous."

Like radiation, these drugs have not been shown to actually extend the survival rate of patients with DCIS—only to reduce the risk of another cancer.

Patients should consider their individual risk factors to decide whether additional treatment is worth it to them, said Dr. Meyers, "and if they feel miserable on these medicines, we can always stop them."

Chemo Isn't Necessary

Because DCIS is non-invasive, chemotherapy is not used as a treatment option. Rarely—in less than 1% of all cancer diagnoses—pathology reports show that cancer cells in a DCIS lesion have started to break through the wall of the duct, known as DCIS with micro-invasion, or DCIS-MI. Chemotherapy may be beneficial in these cases, but more research is still needed.

It Can Happen to Anyone

People of every gender have breast ducts. Thus, cisgender men can get DCIS, but it's rare as it shows up in around 1 in 10 cases.

Because they don't get routine mammograms, breast cancer of any kind often isn't discovered in cisgender men until it has already reached a later stage, when the tumors are large enough to be felt during a physical exam.

Still, treatment and prognosis are generally the same for all people with a similar size and grade tumor, explained Dr. Meyers.

It Can Happen at Any Age

"DCIS can happen to anybody, anytime," said Dr. Meyers, but it's usually diagnosed in people over 40 when many begin getting mammograms. DCIS is not typically found in individuals 30 years of age or younger, but DCIS rates increase with age.

People diagnosed with DCIS under age 50 have a higher recurrence rate or invasive cancer, and therefore more aggressive treatment is usually recommended, said Dr. White. Those over 50, on the other hand, can take comfort in knowing that a diagnosis does not raise their risk of early death.

DCIS Has the Same Risk Factors As Invasive Breast Cancers

Although DCIS is non-invasive, its risk factors are the same for cancers that are. "The same things that increase a woman's risk for DCIS are really the same things that increase her risk of invasive breast cancer," said Dr. Meyers.

For example, having a strong family history can be a factor—especially if a person tests positive for a high-risk BRCA gene mutation.

People with a longer period of estrogen stimulation—meaning they started menstruation early and/or entered menopause late—also have an increased risk of DCIS and invasive cancer. That also goes for people who don't have children or who have their first pregnancy after age 30.

Lifestyle Also Plays A Role

Like risk factors for invasive breast cancers, some risk factors for DCIS are modifiable.

Additionally, for people who have already had DCIS, cutting back on drinking may reduce their risk of recurrence.

"It is possible that alcohol consumption may increase risk of second breast cancer incidence," the authors of one study wrote, "but may not substantially increase the likelihood of aggressive second diagnoses that result in death, particularly among DCIS survivors."

You Can Still Breastfeed After DCIS

Even though DCIS affects the milk ducts, it doesn't necessarily mean you can't produce milk if you become pregnant after diagnosis and treatment.

"As long as a woman has surgery alone, and assuming the lesion is not too close to the nipple, DCIS should not cause problems with conceiving or breastfeeding," explained Dr. Meyers.

If you have been treated with radiation or hormone therapy in addition to surgery, on the other hand, "we usually recommend that a woman see her gynecologist or a fertility doctor to ensure there won't be an issue," added Dr. Meyers.

It Can Be a Controversial Diagnosis for Healthcare Providers

One article talked about how pathologists disagree with one another about 8% of the time when diagnosing breast biopsy samples and that cases of DCIS were the most difficult to reach a conclusion about.

About 19% of DCIS cases were overinterpreted in the study, meaning they were mistakenly categorized as a higher grade or invasive cancer. About 12% were under-interpreted or mistakenly categorized as lower grades.

The authors wrote that non-invasive breast lesions represent a "gray zone" in medicine, where there's not always a right or wrong diagnosis. They said that revised guidelines are needed to make sure DCIS patients get a consistent diagnosis they can trust.

A Vaccine May Be Helpful

Patients diagnosed with DCIS may one day get a vaccine to help reduce their risk of developing invasive breast cancer in the future.

More clinical trials are underway, but researchers have been hoping that a vaccine may be able to stimulate the immune system and keep early DCIS from progressing beyond the milk duct. If trials are successful, experts said it could eventually be an alternative to surgery and radiation for some patients.

A Quick Review

Ductal carcinoma in situ (DCIS) is a non-invasive form of breast cancer that affects breast ducts. DCIS shares some risk factors with invasive breast cancers, and it can affect anyone of any age. However, DCIS can be treated in some of the same ways as other breast cancers in an effort to prevent it from turning into an invasive form of breast cancer.