Radiation and Hormonal Therapy After DCIS Surgery Lowers Recurrence Risk

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A study found that both radiation therapy and hormonal therapy after surgery to remove DCIS (ductal carcinoma in situ) can reduce the risk of the cancer coming back (recurrence) or a new diagnosis. Radiation therapy seems to be better at lowering the risk of cancer in the same (ipsilateral) breast. Hormonal therapy seems to be better at lowering the risk of cancer in the opposite (contralateral) breast. These results were presented at the 2009 San Antonio Breast Cancer Symposium.

DCIS is the most common form of non-invasive breast cancer. DCIS usually is treated with surgery to remove the cancer (usually lumpectomy). After surgery, many women have radiation therapy. If the cancer is hormone-receptor-positive (most are), hormonal therapy medicine also may be prescribed. Because they're given after surgery, both radiation therapy and hormonal therapy are called adjuvant treatments.

In this large study, more than 1,700 women had surgery to remove hormone-receptor-positive DCIS. After surgery, the women got one of four treatments:

  • radiation therapy
  • tamoxifen (hormonal therapy)
  • radiation therapy AND tamoxifen
  • no treatment after surgery

The women got tamoxifen as hormonal therapy because the aromatase inhibitors, another type of hormonal therapy commonly used today, weren't in use when this study started.

The women were followed for more than 10 years. During that time, the researchers kept track of how many women were diagnosed with recurrent DCIS or invasive breast cancer and whether it was in the same breast as the original DCIS or the opposite breast. The researchers wanted to know if the different treatments after surgery made a difference in the risk of DCIS coming back or a new breast cancer being diagnosed.

Radiation Therapy Benefits

Overall, women who got radiation therapy after surgery had a 60% lower risk of recurrence or a new cancer compared to women who got no treatment after surgery. The risk was most reduced for new cancer in the SAME breast as the original DCIS. Radiation therapy didn't really lower the risk of a new breast cancer in the opposite breast.

  • the risk of a new invasive cancer was 68% lower and the risk of new DCIS was 62% lower in women who got radiation compared to women who didn't get radiation
  • the risk of new cancer in the same breast 5 years after the original DCIS diagnosis was 4.4% for women who got radiation therapy compared to 13% for women who didn't get radiation
  • the risk of a new cancer in the same breast 15 years after the original DCIS diagnosis was 7.1% for women who got radiation therapy compared to 21.7% for women who didn't get radiation
  • the risk of a new cancer in the opposite breast was reduced by only 16% overall in the women who got radiation therapy (this difference wasn't statistically significant, which means it could have been due to chance and not because of the radiation); the risk of a new cancer (invasive or non-invasive) in the opposite breast was 3.4% for women who got radiation therapy compared to 4.1% for women who didn't get radiation

Hormonal Therapy Benefits

Overall, women who got tamoxifen after surgery had a 29% lower risk of recurrence or a new breast cancer compared to women who got no treatment after surgery. The risk was most reduced for new cancer in the breast OPPOSITE the original DCIS diagnosis.

  • the risk of invasive breast cancer was 19% lower and the risk of DCIS was 33% lower in women who got tamoxifen compared to women who didn't get tamoxifen
  • the risk of a new cancer in the same or opposite breast 5 years after the original DCIS diagnosis was 13.3% for women who got tamoxifen compared to 16.6% for women who didn't get tamoxifen
  • the risk of a new cancer in the same or opposite breast 15 years after the original DCIS diagnosis was 19.6% for women who got tamoxifen compared to 26.1% for women who didn't get tamoxifen
  • in the OPPOSITE breast, the risk of a new invasive cancer was 53% lower and the risk of new DCIS was 64% lower for women who got tamoxifen compared to women who didn't get tamoxifen
  • in the SAME breast, the risk of a new invasive cancer was 5% lower and the risk of new DCIS was 30% lower in women who got tamoxifen compared to women who didn't get tamoxifen

The results show that both radiation therapy and hormonal therapy after surgery to remove DCIS can reduce the risk of a future DCIS or invasive breast cancer diagnosis. Radiation therapy seems to be better at lowering the risk of cancer in the breast with the original DCIS diagnosis. Hormonal therapy seems to be best at lowering the risk of cancer in the opposite breast.

If you've been diagnosed with DCIS, your doctor will evaluate all of the details of your unique situation and recommend a treatment plan after surgery tailored to your specific risk of recurrence or a new cancer diagnosis. Your treatment plan may include radiation therapy, hormonal therapy, both, or neither. If you're in the process of deciding on treatments after DCIS surgery, you might want to talk to your doctor about this study. By considering the specifics of the cancer, your future risk, and all possible treatment options, you and your doctor 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.

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