MRI tumor volume reduction rate vs tumor regression grade in the pre-operative re-staging of locally advanced rectal cancer after chemo-radiotherapy

Highlights • The study compared the tumor volume reduction rate vs tumor regression grade. • A statistically significant correlation is found between the tumor volume reduction rate and the tumor regression grade after chemo-radiotherapy. • When the tumor volume reduction rate is superior to 85% no residual tumor is found in the pathologic specimen, that means a complete response to chemo-radiation therapy. • The tumor volume reduction rate is a valid parameter of treatment response that should be included in the wider spectrum of quantitative imaging biomarkers already considered in the staging and re-staging of locally advanced rectal cancer.