Enhanced tumorocidal effect of chemotherapy with preoperative radiotherapy for rectal cancer: preliminary results--EORTC 22921.

Purpose: The European Organisation for Research and Treatment of Cancer (EORTC) trial evaluated the addition of chemotherapy (CT) to preoperative radiation (preop RT) and the value of postoperative CT for improving the survival in patients with T3-4 resectable rectal cancer. Patients were allocated to the following four arms: arm 1, preop RT 45 Gy in 5 weeks; arm 2, preop RT plus two 5-day CT courses (fluorouracil 350 mg/m2/d and leucovorin 20 mg/m2/d) in the first and fifth week of RT; arm 3, preop RT plus four postoperative CT courses; and arm 4, preop RT and CT plus postoperative CT. We investigated the effect of adding CT on the pathologic parameters.

Patients And Methods: One thousand eleven patients were entered onto the trial; 505 received preop RT (arms 1 and 3), and 506 received preop RT-CT (arms 2 and 4). We analyzed the differences in tumor size, tumor node stage, number of retrieved nodes, and histologic features such as lymphatic, venous, and perineural invasions, tumor differentiation, and tumor type.

Results: After preop RT-CT, tumors were smaller (P < .0001), had less advanced pT (P < .001) and pN stages (P < .001), had small numbers of examined nodes (P = .046), and less frequent LVN invasions (P < or = .008). Mucinous tumors increased after preop RT-CT (P < .001).

Conclusion: In patients with rectal cancer, preliminary results of EORTC Trial 22921 indicate that the addition of CT to preop RT induces down-sizing, downstaging, and significant changes in histologic characteristics. Longer follow-up is needed to assess the impact on local control and survival.