The difficulty with localization of rectal cancer after neoadjuvant chemoradiation therapy.

Neoadjuvant chemoradiation therapy (NCRT) has become the standard treatment for locally advanced rectal cancer. Subsequent downstaging can make identification of the primary tumor challenging. Complete pathologic response rates of 8 per cent to 27 per cent are seen with current NCRT regimen. Two patients were referred to our institution after NCRT and subsequent low anterior resection in whom no residual cancer was found in the resected specimen but who manifested cancer in the distal rectum in the early postoperative period. Resection of a locally advanced rectal cancer after NCRT associated with significant tumor shrinkage is facilitated by the surgeon's evaluation with proctoscopy and tumor tattooing before the initiation of NCRT. After NCRT, preoperative proctoscopy, distal rectal evaluation after a sphincter sparing procedure in the operating room, and thorough specimen evaluation help to insure that the surgeon has removed the rectal cancer with an appropriate margin. These cases emphasize how important it is for the surgeon to be involved in the staging phase of managing the patient with rectal cancer.