Patients with ductal carcinoma in situ (DCIS) who undergo breast conserving surgery (BCS) are at risk of cancer recurrence. This study aimed to identify risk factors which could predict the likelihood of recurrence. It was found that a low tumor grade, presence of cancerous cells in the area directly around the tumor, the presence of a protein called Ki-67 and radiation therapy following surgery were all associated with increased likelihood of cancer recurrence. 

DCIS is breast cancer which occurs in the milk ducts (tubes which carry milk to the nipples) of the breast and has not spread from these ducts. Survival rates for DCIS are excellent and it is typically treated with surgery, radiation therapy or both. BCS involves removal of part of the breast only. There is however, a higher risk of cancer returning. Identifying risk factors that can predict the likelihood of cancer recurrence is a high priority. This would allow high risk patients to be identified and would help guide further treatment options. 

111 patients with DCIS who had undergone BCS were followed in this study. Cancer returned in 24.3% of patients.

Cancerous cells found in the margin (the edges of the removed tumor and breast tissue) were associated a 10.9-fold increased risk of recurrence. Patients were more at risk of recurrence if this margin around the tumor was less than 1mm.

Patients who did not undergo additional radiation therapy were 78% more likely to have cancer recurrence.  

Patients with high levels of Ki-67 (a protein involved in the creation of new cells) had a 5.5-fold higher risk of cancer recurrence. Recurrence rates were also significantly linked to low tumor grade.

Recurrence rate was not shown to be linked to age, breast cancer subtypes, or hormone therapy. 

This study concluded that low tumor grade, presence of Ki-67, absence of radiation therapy and cancerous cells in the margin surrounding the removed tumor are all associated with higher risk of tumor recurrence.

Further studies with larger patient groups are necessary to determine other potential risk factors.