Interval to surgery after neoadjuvant treatment for colorectal cancer

The current standard treatment of low-lying locally advanced rectal cancer consists of chemoradiation followed by radical surgery.The interval between chemoradiation and surgery varied for many years until the1999 Lyon R90-01 trial which compared the effects of a short(2-wk)and long(6-wk)interval.Results showed a better clinical tumor response(71.7%vs 53.1%)and higher rate of positive and pathologic tumor regression(26%vs 10.3%)after the longer interval.Accordingly,a 6-wk interval between chemoradiation and surgery was set to balance the oncological results with the surgical complexity.However,several recent retrospective studies reported that prolonging the interval beyond 8or even 12 wk may lead to significantly higher rates of tumor downstaging and pathologic complete response.This in turn,according to some reports,may improve overall and disease-free survival,without increasing the surgical difficulty or complications.This work reviews the data on the effect of different intervals,derived mostly from retrospective analyses using a wide variation of treatment protocols.Prospective randomized trials are currently ongoing.