In the largest study of its kind, researchers from the University of Cambridge found that those who drink in moderation are more likely to recover from the illness than those who abstain.
The findings are somewhat unexpected because drinking alcohol is considered to be one of the leading causes of breast cancer among healthy women, the Daily Mail reported.
One explanation is that the chemicals in alcohol which damage healthy cells also have the same effect on cancerous cells.
There are currently no specific guidelines in the UK for breast cancer patients on alcohol consumption, but healthy women are advised to drink no more than 14 units a week.
Many women with cancer stop drinking in the hope it will boost the success of their treatment.
Researchers looked at 13,525 women with breast cancer for an average of seven years.
They recorded the average weekly alcohol intake for each patient as well as their body mass index.
Women who drank seven units a week