Enhancement of radiation-induced downstaging of rectal cancer by fluorouracil and high-dose leucovorin chemotherapy.

Purpose: To determine if fluorouracil (5-FU) plus high-dose leucovorin (LV) enhances local response in patients receiving preoperative radiation therapy (RT) for adenocarcinoma of the rectum, we compared the degree of downstaging in patients receiving preoperative RT with or without chemotherapy.

Patients And Methods: For this comparison, three groups of patients who were treated with identical doses and techniques of preoperative pelvic RT (total dose of 5,040 cGy) were examined. Group 1 included 20 patients with unresectable disease who received combined RT and LV/5-FU. Group 2 included 11 patients with unresectable disease who received preoperative RT. Group 3 included 21 patients with invasive, resectable, primary disease who received preoperative RT.

Results: Patients with unresectable disease who received LV/5-FU had a higher rate of pathologic complete response (20% v 0%) and a lower incidence of positive nodes (30% v 64%) compared with those who did not receive chemotherapy. Even when the most favorable group of patients was included (group 3), patients who received LV/5-FU still had a higher complete response rate (20% v 6%) and a lower incidence of positive nodes (30% v 53%) compared with those who received RT without LV/5-FU. Of those patients with initially unresectable disease, the resectability rate was higher in those who received LV/5-FU compared with those who did not receive LV/5-FU (90% v 64%). Patients who received LV/5-FU experienced slightly more grade 1 to 2 fatigue, stomatitis, nausea, and grade 3 diarrhea, tenesmus, and dysuria.

Conclusions: Despite the fact that patients who received chemotherapy (group 1) had more advanced disease compared with those with resectable disease (group 3), the addition of LV/5-FU increased the resectability and downstaging rates. The ultimate impact of a complete response as well as a decrease in the incidence of pelvic nodes on local control and survival remains to be determined. However, given the enhancement of down-staging in patients with unresectable rectal cancer, we are encouraged by the combined modality approach.