Long-term prognostic value of mesorectal grading after neoadjuvant chemoradiotherapy for rectal cancer.

Background: Mesorectal grading was reported to be a valuable prognostic factor in rectal cancer surgery. Previous studies were retrospective, and had short follow-up.

Objective: To assess the long-term influence of total mesorectal excision quality on disease recurrence in mid and low rectal cancer patients who received preoperative neoadjuvant chemoradiotherapy (CRT) and postoperative chemotherapy.

Methods: One hundred twenty-one patients with rectal cancer had either low anterior resection or abdominoperineal resection. All patients received neoadjuvant CRT and postoperative chemotherapy. Main outcome measures included TNM staging, involvement of the circumferential resection margin (ICRM), mesorectal grading, local and systemic recurrences were recorded.

Results: Follow-up was done for at least 5 years or up to disease recurrence whatever comes first. Mean follow-up time was 59.4 months. Twenty-nine patients had abdominoperineal resection and 92 had low anterior resection. About 7.5% had positive CRM which was significantly correlated with mesorectal grading. Grade 3 mesorectal specimens were obtained in approximately 60% of patients, 27% had grade 2, and only 13% had grade 1 (poor) mesorectal specimens. Poorer mesorectal grading increased with APR and lower rectal tumors. Recurrences occurred in 20% of patients (40% in the first 2 years, 32% in the 3rd year, and 28% in the 4th and 5th years); factors affecting recurrence included lymphovascular invasion, ICRM, and N stage. Mesorectal grading was not a valuable prognostic factor for recurrence unless it resulted in ICRM. Recurrences occurred earlier with poorer mesorectal grade, yet this was not statistically significant.

Conclusions: Mesorectal grading is a pathologic description that reflects the quality of surgery. However, in patients who received neoadjuvant CRT and postoperative chemotherapy, grading had no long-term prognostic value regarding recurrences unless it resulted in ICRM.