Evaluating the effects of tamoxifen after surgery in women with ductal carcinoma in situ

This review analyzed the effect of tamoxifen (Nolvadex) on survival and risk of recurrence (return of the cancer) in patients with ductal carcinoma in situ (DCIS). 

DCIS is a type of early-stage breast cancer. The cancer begins in the milk ducts of the breast breast and stays in its original place (in situ). This is a 'non-invasive' type of cancer meaning that the cancer does not spread from the milk ducts to the surrounding normal tissues. However, the presence of DCIS increases the chance of invasive (spreading of the cancer from the milk ducts to the surrounding normal tissues) cancer later on. Usually, this type of cancer is treated with surgery to remove only the cancerous lump (lumpectomy) or the whole breast (mastectomy). Radiation therapy after surgery significantly decreases the risk of recurrence. Tamoxifen is a hormone therapy drug that has been shown to improve survival and decrease the risk of recurrence in patients with invasive breast cancer. This drug works by blocking the action of estrogen, the main female sex hormone that fuels the growth of some breast cancers. This review examines whether tamoxifen after surgery has any benefits on survival and risk of recurrence in patients with DCIS.

This review included data from two separate clinical trials involving 3375 women with DCIS. All patients underwent surgery to remove the cancer with or without radiotherapy. Patients were randomly assigned to receive either tamoxifen or placebo (a substance with no medical effect used as control when testing new drugs). Overall, tamoxifen given after surgery in patients with DCIS resulted in decreased recurrence in both the same breast (25% reduction) and the opposite breast (50% reduction). Also, there was a lower risk of developing a new invasive breast cancer in both breasts for patients treated with tamoxifen. However, there was no difference in survival rates in patients treated with tamoxifen compared to those who did not receive tamoxifen. Patients receiving tamoxifen reported more side effects such as mood changes, blood clotting problems or cancer of the uterine muscle. 

In summary, tamoxifen with or without radiotherapy after surgery, helped reduce the risk of recurrence in patients with DCIS, with no additional benefits on survival.

However, given that patients also received radiotherapy, it is not clear from this research if tamoxifen alone has the same benefits in patients with DCIS. Also, this study did not specify the characteristics (menopausal status, type of DCIS) of the patients who might benefit from tamoxifen treatment.