Background/aims: The significance of tumor volume and its change after concurrent chemoradiotherapy (CCRT) was evaluated.
Methodology: Standard-dose external radiation and oral UFUR plus leucovorin were used to treat 30 middle and lower rectal adenocarcinoma patients. Volume of tumor calculated from images obtained by dynamic MRI of the rectum before and after CCRT was compared to pathological results after definite resection and other clinical data.
Results: The T-stage in 15 patients (50%), the N-stage in 13 (72.2%), and overall, the TNM stage in 18 (60%), were downstaged, including 7 (23.3%) with complete responses (CR). Volume of tumor before CCRT (Vpre) and after CCRT (VPost) was 10.3+/-6.1cm3 and 4.2+/-2.2cm3, respectively, and VPre correlated with initial T stage, N stage, age, and location. The net decrease ratio (NDR) of tumor volume was related to Vpre and initial T stage. As to the downstaging effect, VPre was related to incidence of CR; NDR was related to the downstaging of the N stage.
Conclusions: All tumors showed volume reduction after CCRT, but the downstaging benefits were not in proportion to the size change. Initially larger tumors had higher ratios of volume reduction, and smaller tumors had higher chance of CR.