Mucinous adenocarcinoma of the rectum: a poor candidate for neo-adjuvant chemoradiation?

Mucinous adenocarcinoma (MA) is a distinct pathological entity associated with poor outcome. Due to different biological behavior, the response to neoadjuvant chemo-radiation (NACRT) may be inferior compared to non-mucinous tumours. In this study we compare the pathological response of mucinous tumours after NACRT.

A total of 183 patients who underwent NACRT for rectal cancer were classified as mucinous and non-MAs. The dose of radiation was 45 Gy (at 1.8 Gy per fraction) delivered over five weeks with weekly 5-flourouracil (5-FU) (325 mg/m(2)) and leucovorin (20 mg/m(2)). After surgery, the pathological specimens were evaluated and staged. The data are reported as descriptive statistics and chi-square test used to determine difference in proportions.

The two varieties were comparable on the basis of the computed tomography (CT) scan in terms of tumour size and lymph node metastasis. However in terms of pathological response, it was seen that there was a higher incidence of pT4 tumours (73.5% vs. 10.7%), margin positivity (11.7% vs. 2.3%) and advanced nodal disease pN2 (29.4% vs. 9.3%) in mucinous and non-mucinous tumours respectively.

MA of the rectum show a poor response to NACRT as seen in terms of larger residual tumours, higher incidence of margin positivity, and greater residual nodal disease. Also they showed higher incidence of peritoneal and distant dissemination during NACRT. The role of NACRT in mucinous carcinoma of the rectum is of questionable benefit and needs to be examined in prospective trials.