Pathological response following long-course neoadjuvant chemoradiotherapy for locally advanced rectal cancer

Aims : To standardize the pathological analysis of total mesorectal excision specimens of rectal cancer following neoadjuvant chemoradiotherapy for locally advanced disease (T3/T4), including tumour regression. Methods and results : Standardized dissection and reporting was used for 60 patients who underwent total mesorectal excision following long‐course chemoradiotherapy. Tumour regression was scored by two pathologists (K.S., D.G.) using both an established 5‐point tumour regression grade (TRG), and a novel 3‐point grade. Both scores were evaluated for interobserver variability. A complete or near‐complete pathological response (3‐point TRG 1) was found in 10 patients (17%). Using the 5‐point TRG, there was good agreement between both pathologists (κ = 0.64). Using the 3‐point grade, agreement was excellent (κ = 0.84). No disease recurrence has been reported in patients with a complete, or near complete pathological response (3‐point TRG 1), after a mean follow‐up of 22 months. Conclusion : Tumour regression grade is a useful method of scoring tumour response to chemoradiotherapy in rectal cancer. TRG 1 and 2 can be regarded as a complete pathological response (ypT0). A modified 3‐point grade has the advantage of better reproducibility, with similar prognostic significance.