Table 1. Histological tumour regression grading systems.

Grade	Definition
Dworak et al (1997)
0	No regression
1	Dominant tumour mass with obvious fibrosis and/or vasculopathy
2	Dominantly fibrotic changes with few tumour cells or groups (easy to find)
3	Very few (difficult-to-find microscopically) tumour cells in fibrotic tissue with or without mucous substance
4	No tumour cells, only fibrotic mass (total regression or response)
Mandard et al (1994) (adapted by Bouzourene et al, 2002)
5	Absence of regressive changes
4	Residual cancer outgrowing fibrosis
3	Increase in the number of residual cancer cells, but fibrosis still predominant
2	Presence of rare residual cancer cells scattered through the fibrosis
1	Complete regression, absence of histologically identifiable residual cancer and fibrosis extending through the different layers of the rectal wall, with or without granuloma