Methods: The study enrolled 278 patients scheduled for preoperative CRT using two protocols with different chemotherapeutic regimens. Pelvic radiotherapy (50.4 Gy) was delivered concurrently with FL (n = 145) or capecitabine (n = 133). Surgery was performed 6 weeks after CRT completion. Tumor responses to CRT were measured using both radiologic and pathologic examination. Magnetic resonance volumetry was performed at the initial workup and just before surgery after completion of preoperative CRT. Post-CRT pathology tests were used to determine tumor stage and regression.

Results: Radiologic examination showed that tumor volume decreased by 68.2 % ± 20.5 % in the FL group and 68.3 % ± 22.3 % in the capecitabine group (p = 0.970). Postoperative pathologic T stage determination showed that downstaging occurred in 44.3 % of FL and 49.9 % of capecitabine patients (p = 0.571). The tumor regression grades after CRT were Grade 1 (minimal response) in 22.6 % and 21.0 % , Grade 2 (moderate response) in 53.2 % and 50.0 % , Grade 3 (near-complete response) in 12.9 % and 12.9 % , and Grade 4 (complete response) in 11.3 % and 16.1 % of the FL and capecitabine groups, respectively (p = 0.758).

Conclusion: In the present study, the radiologic and pathologic findings did not reveal significant differences in short-term tumor responses between preoperative FL and capecitabine CRT for locally advanced rectal cancer. Long-term results and a prospective randomized trial are needed.