Breast Cancer Study Encourages Reconsideration of DCIS (Ductal Carcinoma In Situ) and its Treatment

by Mary E. Costanza, MD

Women who are diagnosed with a very early stage of breast cancer usually undergo some type of surgery with the hope that it will eliminate their risk of developing invasive breast cancer. The most common treatment is lumpectomy followed by radiation, though some women opt for a mastectomy or even a double mastectomy, which involves removing a healthy breast as well.

A new study published this month shows that in most cases, treatment does not affect a woman’s outcome, throwing into question whether surgical treatments have been overly aggressive and overused.

This early cancer stage is known as ductal carcinoma in situ (DCIS) and is commonly referred to as Stage 0. With DCIS, abnormal cells develop from cells that line the milk ducts; however, these abnormal cells have not invaded the surrounding breast tissue.

Increased mammogram screening has led to an increase in DCIS diagnoses in recent years. The American Cancer Society estimates that about 60,290 new cases of DCIS will be diagnosed in women in 2015, along with nearly 232,000 new cases of invasive breast cancer. About 40,290 women will die from breast cancer this year.

In August, the cancer journal JAMA Oncology published two important papers about DCIS that tests our understanding of DCIS and its role in invasive breast cancer. The first, “Breast Cancer Mortality After a Diagnosis of Ductal Carcinoma In Situ,” found that half the time invasive breast cancer develops, it has not developed from a prior DCIS. This finding challenges the orthodox view that DCIS is the original tissue from which most invasive ductal carcinomas (the most common form of breast cancer) develop.

This probably means DCIS is a marker – a woman may have cells somewhere in the breast that either are or will become invasive cancer, but these cells are currently undetectable. In other words, DCIS is functioning more as a risk factor rather than a direct cause in at least half of all breast cancer deaths.

According to the study:

• 1.1 percent of women with DCIS had died of invasive breast cancer by the 10-year mark and 3.3 percent of women by the 20-year mark. These rates, while low, are almost twice that for the U.S. population.

• More than half the breast cancer deaths in DCIS women were not associated with an invasive in-breast recurrence. This fact suggests that local therapy alone is not enough to treat “aggressive” DCIS.

• Local therapy (surgery and/or radiation therapy) decreased the in-breast invasive cancer rate. However, it did not reduce the death rate from invasive cancer. DCIS that did recur in the breast as invasive disease was associated with a higher mortality rate.

This study is important because it is huge – reporting on over 100,000 women with DCIS – and because it is based on well-established survey data from 18 different U.S. cancer registries. Its findings are similar to those from a much smaller and earlier study from Sweden. The fact that two different studies have reported the same general conclusions makes these findings more believable.

A number of factors were identified that predict whether invasive breast cancer and death are more likely to occur. The death rate was higher in black women and in women who were diagnosed before age 35, making both of these key risk factors. Additional risk factors include:

• a DCIS that is larger than 1 cm. (1/2 inch).

• a DCIS that is insensitive to hormones (no estrogen or progesterone receptors).

• a DCIS that is of higher grade (more cancer-like).

• a DCIS showing increased cell death (comedonecrosis).

While these factors have been suspect for some time, having them confirmed in such a large study makes us more comfortable in sorting out which DCIS patients are more or less likely to die from an invasive breast cancer.

For DCIS types associated with high risk factors, it may be more beneficial to consider systemic therapies, like chemotherapy or hormonal therapy.

The second paper published in JAMA, “Rethinking the Standard for Ductal Carcinoma in Situ Treatment,” reviews treatment options in light of these new findings.

So, what should you do if you are diagnosed with DCIS?

As always, the best advice is to get a second opinion, and the best place to get it is at a well-known and respected breast cancer center. Their experts will evaluate your risks and discuss with you all the treatment options available. With the identification of factors more likely to be associated with death, there is now the real possibility of tailoring treatment depending on a woman’s individual risk.

Remember the good news is that all DCIS tumors are not the same – some are associated with higher risk for breast cancer death; others are not.

In addition, 97 percent of the time, DCIS does not result in a death from breast cancer. And if you have few or none of the high-risk conditions, your prognosis is even better that 97 percent.

Mary E. Costanza, MD, is a professor of medicine at University of Massachusetts Medical School.