Histological grading based on poorly differentiated clusters is predictive of tumour response and clinical outcome in rectal carcinoma treated with neoadjuvant chemoradiotherapy.

PDC grade may be assessed in preoperative biopsies of rectal cancer with good reproducibility. High PDC grade in a pretreatment tumour is significantly associated with a poor response to therapy. Hence, we suggest that PDC grading might be used as a significant predictive and prognostic factor in patients with locally advanced rectal cancer who are treated with neoadjuvant CRT, and to identify high-risk patients who need surgery and adjuvant chemotherapy.