Sequential preoperative fluorodeoxyglucose-positron emission tomography assessment of response to preoperative chemoradiation: A means for determining longterm outcomes of rectal cancer

BACKGROUND: We have previously demonstrated that fluorodeoxyglucose-positron emission tomography (FDG-PET) can assess extent of pathologic response of primary rectal cancer to preoperative chemoradiation. Our goal was to determine the prognostic significance of FDG-PET assessment of rectal cancer response to preoperative chemoradiation. STUDY DESIGN: Fifteen patients with locally advanced primary rectal cancer (clinically bulky or tethered, or ultrasound evidence of T3-4 disease, N1 disease, or both) deemed eligible for preoperative radiation and 5-FU-based chemotherapy (5,040 cGy to the pelvis and 2 cycles of bolus 5-FU/leucovorin) were prospectively enrolled from May 1997 to September 1998. FDG-PET was performed before and 4 to 5 weeks after completion of preoperative chemoradiation. FDG-PET parameters included maximum standard uptake value (SUVmax), total lesion glycolysis (TLG), and visual response score. Patients were prospectively followed after operation, and disease status was determined. RESULTS: All patients demonstrated some degree of response to preoperative therapy based on pathologic examination. At a median followup of 42 months (range 23 to 54 months), 11 patients had no evidence of disease and 4 had died of disease. The mean percentage decrease in SUVmax (DeltaSUV(max)) was 69% for patients free from recurrence and 37% for patients with recurrence (p = 0.004). DeltaSLTV(max) greater than or equal to 62.5 and deltaTLG greater than or equal to 69.5 were the best predictors of no-evidence-of-disease status and freedom from recurrence. Patients with DeltaSUV(max) greater than or equal to 62.5 and deltaTLG greater than or equal to 69.5 had significantly improved disease-specific and recurrence-free survival (p = 0.08, 0.02 and p = 0.03, 0.01, respectively). CONCLUSIONS: Our results indicate that FDG-PET assessment of locally-advanced rectal cancer response to preoperative chemoradiation may predict longterm outcomes. (C) 2004 by the American College of Surgeons.