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

Abstract

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. 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 (SUV(max)), total lesion glycolysis (TLG), and visual response score. Patients were prospectively followed after operation, and disease status was determined. 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 SUV(max) (DeltaSUV(max)) was 69% for patients free from recurrence and 37% for patients with recurrence (p = 0.004). DeltaSUV(max) >or= 62.5 and deltaTLG >or= 69.5 were the best predictors of no-evidence-of-disease status and freedom from recurrence. Patients with DeltaSUV(max) >or= 62.5 and deltaTLG >or= 69.5 had significantly improved disease-specific and recurrence-free survival (p = 0.08, 0.02 and p = 0.03, 0.01, respectively). Our results indicate that FDG-PET assessment of locally-advanced rectal cancer response to preoperative chemoradiation may predict longterm outcomes.