does time of day affect quality of breast cancer surgery?

background: time of day can affect the outcome of medical procedures and surgical operations. the current study was designed to assess whether time of day can influence the quality of breast cancer surgery or not. methods: patients who underwent breast cancer surgery and axillary lymph node dissection in tehran, iran between march 2012 and march 2013 were enrolled. surgeries were categorized into two group based on the time of initiation (before and after 1 pm). we considered the number of dissected lymph node as an indicator of operation quality. in this way, dissection of at least six lymph nodes was considered as an adequate number of lymph node examinations. results: a total of 134 patients were enrolled. median start time of surgery was 11 am. surgeries were performed before and after 1 pm in 105(78.4%) and 29(21.6%) patients, respectively. the association between time and the number of dissected lymph nodes was significant when they were considered either as a categorical (p = 0.002) or continuous variables (p = 0.039). conclusions: based on our results, it can be suggested that breast surgeries with later start time might have lower quality.