A study found that radiation therapy and hormonal therapy after surgery for DCIS (ductal carcinoma in situ) reduces the risk of being diagnosed with either another DCIS or invasive breast cancer in the future. Radiation therapy lowers the risk of cancer in the same (ipsilateral) breast as the original DCIS. Hormonal therapy lowers the risk of cancer in the same or the opposite (contralateral) breast. These results were presented at the 2010 San Antonio Breast Cancer Symposium (SABCS).
DCIS is the most common form of non-invasive breast cancer. DCIS usually is treated with surgery to remove the cancer, lumpectomy in most cases. After surgery, many women have radiation therapy. If the DCIS is hormone-receptor-positive (most are), hormonal therapy medicine also may be recommended, either instead of or in addition to radiation therapy. Treatments given after surgery to reduce future risk are called adjuvant treatments.
In this large study, 1,701 women had surgery to remove hormone-receptor-positive DCIS. After surgery, the women got one of three treatments:
- radiation therapy only
- tamoxifen (hormonal therapy) only
- radiation therapy and tamoxifen
Ultimately, 1,576 women got tamoxifen, either alone or in addition to radiation therapy; 1,030 women got radiation therapy, either alone or in addition to tamoxifen.
The women in this study got tamoxifen as hormonal therapy because the aromatase inhibitors, another type of hormonal therapy commonly used today, weren't available when this study started.
The women were followed for nearly 13 years. The researchers kept track of how many women were diagnosed with a new DCIS or invasive breast cancer and whether the new breast event was in the same breast or the opposite breast.
The study was designed so the researchers could see how much each treatment helped reduced the risk of being diagnosed with either a new DCIS or invasive breast cancer in either breast.
Radiation Therapy Benefits
Ten years after DCIS surgery, women who got radiation therapy were 59% less likely to have had new DCIS or invasive breast cancer in the same breast as the original DCIS than women who didn't get radiation therapy. For every 100 women treated with radiation therapy after DCIS surgery, a new breast event in the same breast was prevented in 12.3 women (the absolute risk of a new breast event in the same breast was reduced by 12.3%).
After nearly 13 years of follow-up, the women who got adjuvant radiation therapy were:
- 62% less likely to be diagnosed with a new DCIS in the same breast
- 68% less likely to be diagnosed with invasive breast cancer in the same breast
Radiation therapy didn't lower the risk of a new breast event in the opposite breast. This makes sense because the benefits of radiation would only be in the breast that was treated.
The researchers also found that:
- adjuvant radiation therapy benefited women whether or not they got adjuvant tamoxifen
- adjuvant tamoxifen didn't enhance the benefits of adjuvant radiation therapy in the breast where DCIS was originally diagnosed
- adjuvant radiation therapy seemed to most benefit women with intermediate and high grade DCIS
Pathologists assign a grade to DCIS cells based on how abnormal the cells appear and behave when compared to healthy breast cells. The lower the grade, the more normal the cancer cells look, the more slowly they grow, and the less likely they are to spread. There are three grades of DCIS: low or grade 1, moderate or grade 2, and high or grade 3.
Hormonal Therapy Benefits
Overall, women who got adjuvant tamoxifen were 29% less likely to have any new breast cancer event, either in the same or opposite breast. For every 100 women treated with tamoxifen after DCIS surgery, a new breast event was prevented in 6.5 women (the absolute risk of a new breast event was reduced by 6.5%).
After 10 years, the women who got adjuvant tamoxifen were:
- 30% less likely to be diagnosed with new DCIS in the same breast
- 56% less likely to have a new breast event -- either a new DCIS or invasive breast cancer -- in the opposite breast
The researchers also found that:
- adjuvant tamoxifen reduced the overall risk of any new breast event only in women who didn't get adjuvant radiation therapy
- adjuvant tamoxifen didn't reduce the risk of invasive breast cancer in the same breast (unlike adjuvant radiation therapy)
- adjuvant tamoxifen seemed to offer the most benefit to women with low grade DCIS
This study shows that both radiation therapy and hormonal therapy after surgery to remove DCIS can reduce the risk of new breast cancer events. Still, each treatment has different benefits. Radiation therapy lowers the risk of cancer in the breast where the original DCIS was diagnosed. Hormonal therapy offers more modest benefits to both breasts, but is best at lowering the risk of invasive breast cancer in the opposite breast.
If you've been diagnosed with DCIS, your doctor will recommend a treatment plan after surgery tailored to your specific risk of recurrent DCIS or invasive breast cancer. Your treatment plan may include radiation therapy, hormonal therapy, both, or neither. If you're deciding on treatments after DCIS surgery, you might want to talk to your doctor about this study. Together, you can decide on a treatment plan that makes the most sense for you and your unique situation.
The Breastcancer.org DCIS pages contain more information on DCIS symptoms, diagnosis, and treatment.