Is it better to have radiotherapy or not for ductal carcinoma in situ?

This paper studied whether observation or radiotherapy after breast-conserving surgery (surgery to remove part of breast) was better for patients with ductal carcinoma in situ. 

Ductal carcinoma in situ describes cancer that starts in the milk ducts of the breast, and that has not spread to surrounding breast tissue. Studies have found that radiotherapy reduced the risk of local failure (cancer  spreading to breast tissue or returning) when added to breast conserving therapy (removing some of the breast tissue); these treatments together were associated with outcomes similar to mastectomy (removing all breast tissue). It is important to know whether breast conserving surgery and radiation is better than surgery alone, given that radiation therapy can also be associated with side-effects. 

Women with good risk (low risk) ductal carcinoma in situ who had undergone breast-conserving surgery were studied. This meant that  their cancer cells closely resembled normal cells and the tumour was less than 2.5 cm. All patients received tamoxifen (Nolvadex). Patients were randomly assigned to receive radiation or observation (no treatment) following surgery. Patients were followed-up on their local failure (cancer spread into the breast tissue or return of cancer).

Patients were followed up for an average 7.17 years. After 5 years, 0.4% of patients receiving radiation and 3.5% of patients being observed had a local failure. After 7 years, 0.9% of patients receiving radiation and 6.7% of patients being observed had a local failure.

After 7 years, 1.5% of patients receiving radiotherapy and 2.8% of patients being observed had a mastectomy. The overall survival and disease-free survival (no worsening of disease) rates were excellent and not different between patients receiving radiation or observation.

With regards to adverse events (undesired effect of treatment), 76% of patients receiving radiotherapy and 30% of patients receiving observation had a low or moderate level of toxicity. 4% of patients receiving radiation and 4% of patients being observed had a severe but not life-threatening toxicity. 

The authors concluded that the addition of radiotherapy reduced the local failure rate in good-risk patients with ductal carcinoma in situ.

Longer term studies are needed. 

If considering breast-conserving therapy in ductal carcinoma in situ, discuss with your doctor whether radiation therapy or observation is more suitable for your breast cancer.