DCIS (ductal carcinoma in situ) is the most common form of non-invasive breast cancer and is considered stage 0 cancer. While DCIS isn’t considered life threatening, it does increase the risk of developing invasive breast cancer later in life.
DCIS usually is treated with surgery to remove the cancer -- lumpectomy in most cases. After surgery, hormonal therapy may be recommended if the DCIS is hormone-receptor-positive (most are). Radiation therapy also is recommended for many women. Both hormonal therapy and radiation help reduce the risk of the DCIS recurring (coming back), as well as the risk of invasive cancer.
Routine radiation therapy after DCIS was common in the past, but some newer DCIS treatment guidelines say that women at low-risk for recurrence may be able to skip radiation therapy after surgery. Still, the definition of low-risk isn't always clear.
A study has found that for women diagnosed with DCIS considered to have a low risk of recurrence treated with lumpectomy without radiation, the risk of DCIS recurrence or developing invasive disease in the same breast increased through 12 years of follow-up and didn’t level off.
The study was published online by the Journal of Clinical Oncology on Sept. 14, 2015. Read the abstract of “Surgical Excision Without Radiation for Ductal Carcinoma in Situ of the Breast: 12-Year Results From the ECOG-ACRIN E5194 Study.”
The study included 665 women diagnosed with DCIS that was considered low-risk based on the characteristics of the disease.
The women were divided into two groups based on the characteristics of the DCIS:
- Group one included DCIS that was low- or intermediate-grade and was 2.5 cm or smaller in size (561 women).
- Group two included DCIS that was high-grade and was 1 cm or smaller in size (104 women).
All the women had lumpectomy to remove the DCIS. About 30% of the women in the study took tamoxifen after lumpectomy -- 31% of the women in group one took tamoxifen and 24% of the women in group two took tamoxifen. None of the women had radiation.
After 12 years of follow-up, a total of 99 cases of DCIS or invasive cancer were diagnosed in the same breast in the women:
- 75 were diagnosed in group one
- 25 were diagnosed in group two
- 51 of these were invasive breast cancer (39 in group one and 12 in group two)
The risk of being diagnosed with either a DCIS recurrence or invasive disease in the same breast after 12 years was:
- 14.4% for group one
- 24.6% for group two
The risk of being diagnosed with invasive breast cancer in the same breast 12 years after a DCIS diagnosis was:
- 7.5% for group one
- 13.4% for group two
For both groups, the risk of being diagnosed with either a DCIS recurrence or invasive disease in the same breast increased over time from the first year of follow-up to the 12th year and didn’t level off.
There were no differences between the two groups in overall survival (how long the women lived, whether or not the DCIS came back or invasive disease was diagnosed) or in the rate of DCIS or invasive breast cancer diagnosed in the opposite breast.
Several other large, randomized studies have shown that radiation after lumpectomy for DCIS reduces the risk of recurrence in the same breast by about half. Other studies have shown that taking tamoxifen after lumpectomy for hormone-receptor-positive DCIS reduces the risk of both DCIS recurrence and invasive disease in both breasts.
Still, no study has shown that radiation or tamoxifen after lumpectomy for DCIS improves overall survival or reduces the rate of metastatic recurrence (cancer coming back in a part of the body away from the breast).
How DCIS considered to have a low risk of recurrence should be treated is somewhat controversial right now. Some women and their doctors prefer careful monitoring instead of surgery, some prefer lumpectomy alone, and some prefer lumpectomy followed by radiation and hormonal therapy.
This study found that the risk of invasive breast cancer after a diagnosis of low-risk DCIS treated with lumpectomy alone ranged from 7.5% to 13.4%. Some women may find that risk acceptable. Other women may find that risk unacceptable and want more treatments after surgery.
While the study had 12 years of follow-up, which is a long time, the research did have some weaknesses. It’s important to know that the study didn’t look at whether the women diagnosed with DCIS had other breast cancer risk factors, such as a strong family history of breast cancer or a known abnormal gene. To accurately assess a woman’s risk of invasive disease and develop a treatment plan for DCIS, doctors have to look at ALL risk factors.
Also, the study was non-randomized, which means the women weren’t randomly assigned to a specific treatment group. While none of the women had radiation after surgery, different percentages of women in each group took tamoxifen to reduce the risk of DCIS recurrence or invasive disease, so it's not clear if this affected the study’s outcomes.
There were also only 104 women in group two, the high-grade DCIS group, which is a relatively small number compared to the 561 women in group one.
It’s also important to know that there have been new developments in testing since this study was started. The Oncotype DX DCIS test is a genomic test that analyzes 12 genes in a DCIS and assigns a Recurrence Score that estimates the risk of both DCIS coming back and invasive disease in the future. It gives women and their doctors more information so they can make more informed decisions about whether treatment is needed after DCIS has been surgically removed.
If you’ve been diagnosed with DCIS, the goal is to provide you with the best treatment for your unique situation. This takes into account:
- your family history of breast cancer and other diseases
- your personal health history
- any other breast cancer risk factors you may have
- your preferences
- the characteristics of the DCIS
- any genomic test results
Together, you and your doctor will develop a DCIS treatment plan that makes the most sense for you.
For more information, visit the Breastcancer.org DCIS pages.