Distal Tumor Spread in Rectal Cancer—How Low Should We Go?

Background: Distal tumor spread (DTS) is an adverse prognostic factor in rectal cancer correlating with advanced stage disease. We aimed to assess prevalence and location of distal tumor spread and impact of neoadjuvant chemoradiotherapy (NACRT) in patients who underwent proctectomy for rectal cancer. Methods: The pathology database at our institution was queried for all patients who underwent proctectomy with curative intent for rectal cancer from 1/2008 to 12/2016. Specimen slides were re-evaluated by a single expert rectal cancer pathologist to verify diagnosis and measure the distance to the distal resection margin. Main outcome measures were 3-year overall and disease-free survival. Results: 275 consecutive patients were identified. 109/111 patients with clinical stage 3 disease received preoperative neoadjuvant chemoradiotherapy. DTS was found in 13 (4.7%) specimens, 6 with intra-mural and 7 with extra-mural distal tumor spread. DTS was found only in patients with clinical stage 3 disease. Length of DTS from the distal end of the tumor ranged from 0 to 30 mm; in only 4 specimens DTS was >10 mm. A positive distal resection margin was found in 5/275 (1.8%) specimens. Conclusion: A macroscopically tumor-free margin may suffice in patients with pre-treatment stage 1 or 2 disease. Furthermore, a 1 cm margin is adequate in most patients with stage 3 disease.