Local excision of low rectal cancer treated by chemoradiotherapy: is it safe for all patients with suspicion of complete tumor response?

Purpose: The purpose of this study is to assess if local excision (LE) could be proposed if suspicion of complete tumor response (CR) after neoadjuvant chemoradiotherapy (CRT) for low rectal cancer (LRC) and this despite a potential risk of nodes (N+) or other tumor deposits (OTD) left in place. The aim was to assess in patients with LRC treated by CRT: (a) pathologic results of LE and total mesorectal excision (TME) in case of preoperative suspicion of CR and (b) the risk of N+ or OTD on TME if ypT0-Tis-T1 tumor.

Patients: Among 202 patients with LRC after CRT, 33 (16 %) with suspicion of CR underwent LE (n = 20) because of comorbidities and/or indication of definitive stoma or TME (n = 13). Pathologic examination of LE and TME specimens and oncological outcomes were assessed. Furthermore, 40/202 patients with pathologic CR on TME specimen (ypT0-Tis-T1) were assessed for possible N+ or OTD.

Results: In the 33 patients with suspicion of CR: (a) after LE, tumor was ypT0-Tis-T1 in only 15/20 cases (75 %); (b) after TME, tumor was ypT0-Tis-T1 in only 7/13 cases (54 %). Among 40 patients with ypT0-Tis-T1 tumor on TME specimen, 4 (10 %) presented N+ and/or OTD.

Conclusion: In LRC with suspicion of CR after CRT, LE deserves a word of caution: 25 % of patients have in fact ypT2-T3 tumors. Furthermore, in patients with ypT0-Tis or T1 on TME specimen, a 10 % risk of N+ and/or ODT is observed. Thus, patient with suspicion of CR after CRT and treated by LE is exposed to a possible incomplete oncologic treatment.