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New Research Shows a Long-Term Benefit of Radiation Therapy in Early Breast Cancer

William Peters, M.D., Ph.D

October 23, 2020

A study of over 10,000 patients followed for more than 25 years with an early form of breast cancer has shown that adding radiation therapy to surgery offers better outcomes than surgery alone. Representatives from the Netherlands Cancer Institute presented their findings at the recent European Breast Cancer Conference.

What is DCIS?
Ductal carcinoma in situ (DCIS) is an early form of breast cancer in which the cells that line the milk ducts have turned into cancer cells but have not yet invaded other parts of the breast. About 20% of cancers detected on screening mammography are DCIS. The usual treatment for patients with DCIS has been breast-conserving surgery (lumpectomy). Radiation therapy has been standard therapy as well as hormonal therapy of the DCIS was estrogen receptor-positive. Fortunately, the long-term prognosis for these early cancers is excellent, and survival is over 97%. Nonetheless, about 10-15% of these early cancers can recur or progress into invasive cancer. There has been controversy over the years on whether radiation therapy was necessary after lumpectomy, and that is where this long-term follow-up study is beneficial.

The study reported on 10,045 patients followed for over 25 years after the diagnosis and treatment of DCIS. The results demonstrated that adding radiation therapy to lumpectomy could reduce the risk of invasive breast cancer in half and that the benefit was long-lasting.

Reducing Risk of Recurrence
This extensive study showed that in the first ten years after diagnosis, women who only had breast-conserving surgery (lumpectomy) had a risk of getting DCIS again of 13% (130 cases in 1000 women) but including radiation reduced the DCIS risk to 4.6% (46 out of 1000) – nearly a 70% reduction. Similarly, adding radiation treatment after lumpectomy reduced the risk of developing the more severe invasive cancer from 13.9% to 5.2%. The study also showed that patients who had a mastectomy had the lowest rates of subsequent DCIS or invasive cancer. Still, other research has shown that overall survival with mastectomy is the same as with breast-conserving surgery, and many consider that mastectomy would be overtreatment.
This study also looked at the second ten years after treatment and found that the risks of DCIS and invasive cancer were similar between both with and without added radiation therapy, but the benefit seen during the first ten years persisted.

Evidence-Based Guidance
Even better, the study confirmed that the overall risk of dying from cancer in the 20 years following treatment for women with DCIS is only 1-2%.
Overall, this is excellent information for guiding the decision for women when facing this common diagnosis. We have tried and true guidance that shows survival with breast-conserving surgery and radiation therapy is excellent out to 20 years and reduces the risks of recurrence of DCIS or invasive cancer.

Key Takeaways

  • DCIS is a common early form of breast cancer
  • The survival rates are promising for a DCIS diagnosis, however, there is a risk of recurrence that can sometimes be invasive
  • A new long-term study followed over ten thousand women for over 25 years to determine the benefit of treatment options (lumpectomy, mastectomy, and radiation therapy)
  • The study showed that adding radiation therapy after lumpectomy reduced the risk of developing the more severe invasive cancer from 13.9% to 5.2%.
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