PURPOSE: To evaluate the impact of tumor response; tumor and nodal downstaging; and cTNM, yTNM (clinical stage after chemoradiation, based on preoperative imaging), and pTNM classifications on long-term outcome in patients with rectal cancer treated with preoperative 5-fluorouracil (5-FU)-based concurrent chemoradiation. METHODS AND MATERIALS: Between January 1990 and March 1998, 165 consecutive patients with locally advanced extraperitoneal cancer of the rectum were treated with preoperative chemoradiation. Four patients had a cT2 lesion (2.5%), 120 had a cT3 lesion (74.5%), and 41 had a cT4 lesion (23%). The nodal involvement at combined imaging was cN0 in 21%, cN1 in 41%, cN2 in 34%, and cN3 in 4%. Preoperative chemoradiation was delivered according to 1 of 3 schedules: (1) FUMIR-T3 (from 1990 to 1995) for patients with cT3N0-2 or cT2N1-2 rectal carcinoma (82 patients): 37.8 Gy (1.8 Gy/fraction) plus 5-FU, 1 g/m(2)/d on Days 1-4, continuous infusion, and mitomycin-C, 10 mg/m(2)/d on Day 1; (2) FUMIR-T4 (from 1990 to 1999) for patients with cT4N0-3 or cT3-4N3 rectal carcinoma (40 patients): 45 Gy (1.8 Gy/fraction) plus 5-FU, 1 g/m(2)/d on Days 1-4 and 29-32, continuous infusion, and mitomycin-C, 10 mg/m(2)/d on Days 1 and 29; and (3) PLAFUR-4 (from 1995 to 1998) for patients with cT3N0-2 or cT2N1-2 rectal carcinoma (42 patients): 50.4 Gy (1.8 Gy/fraction) plus 5-FU, 1 g/m(2)/d on Days 1-4 and 29-32, continuous infusion, and cisplatin, 60 mg/m(2)/d on Days 1 and 29. Four to five weeks after chemoradiation, patients were reevaluated for clinical response by imaging studies (CT scan, transrectal ultrasonography, barium enema, liver ultrasonography, chest X-rays) and restaged (yTNM). Surgery was performed 6-8 weeks after chemoradiation. Adjuvant chemotherapy (5-FU + l-folinic acid) was delivered to 26 patients in the FUMIR-T4 protocol group. Local control (LC), freedom from distant metastases (FDM), disease-free survival, and overall survival (OS) were evaluated according to the clinical response and cTNM, yTNM, and pTNM classification. The median follow-up was 67 months. RESULTS: The 5-year survival rate was 100% for cT2, 77% for cT3, and 62% for cT4 (p = 0.0497); after chemoradiation, it ranged between 81% and 91% for pT0-pT2 and dropped to 66% for pT3 and 47% for pT4 (p = 0.014). The 5-year local control rate was, at the first staging, 84% for cT3 and 72% for cT4; after chemoradiation, the pT stage correlated significantly with LC (p = 0.0012): 100% for pT0, 83% for pT1, 88% for pT2, 79% for pT3, and 46% for pT4. N stage was statistically significant in predicting FDM and OS at any staging step. A significant impact of tumor response, tumor downstaging, and nodal downstaging on LC, FDM, disease-free survival, and OS was also recorded. If the residual tumor, before surgery, had a tumor index <30 (i.e., width less than one-quarter of rectal circumference and length in its caudocranial axis < or =30 mm), the 5-year LC, FDM, disease-free survival, and OS rates were significantly higher at both the univariate and the multivariate analyses. The surgical procedure was tailored according to tumor downstaging, and thus the choice of sphincter-preserving surgery was based on the distance between the lower pole of the tumor and the anorectal ring "after" chemoradiation. In 36 patients with the lower pole of the lesion in the range of 0-30 mm from the anorectal ring, 16 patients (44%) underwent a sphincter-saving procedure. All clinical outcomes were similar compared with 20 patients with tumor located at the same rectum level who received an abdominoperineal resection. CONCLUSION: After preoperative chemoradiation, clinical response and tumor/nodal pathologic downstaging showed a close correlation with improved outcomes. The better 5-year survival and local control in pT0-2 patients regardless of their initial stage seems to confirm a heterogeneity in rectal cancer patients. The responder population showed a behavior similar to rectal cancer diagnosed at Stage cT1-2 and treated with conservative surgery alone. Additional studies aimed at improving local tumor response seem justified. Trials of sphincter-saving surgery after a major response are warranted.