Prognostic significance of delayed complete metabolic response on PET/CT after primary chemoradiation treatment of cervical cancer

Objective To investigate the prognostic significance of near-complete metabolic response on initial follow-up PET/CT after primary chemoradiation treatment of cervical cancer.Methods Survival data were retrospectively compared between patients who had complete metabolic response on first follow-up PET/CT, 3 months after chemoradiation (group 1) with those who had near-complete metabolic response on first PET/CT and later showed complete metabolic response at subsequent PET/CT, 6 months or more after treatment (group 2).Results Of the 108 patients included in the final analysis, 74 (68.5%) showed complete metabolic response on initial PET/CT, 3 months after treatment, and 34 patients (31.5%) showed complete metabolic response on subsequent PET/CT, 6 months after treatment. Tumor characteristics were comparable between groups. Group 1 had higher percent of stage 1 (12% vs 0%) and lower percent of stage 4 disease (3% vs 14%) than those of group 2. Group 2 patients had significantly fewer cases of recurrences and deaths than group 1 patients (6% vs 26%, p=0.018; 0% vs 20%, p=0.003, respectively), with comparable 3-year survival rates (group 1, 90% vs group 2, 100%, p=0.31). Twelve patients had progressive disease on first follow-up PET/CT; these patients had significantly worse overall survival compared with all other patients (log-rank test, p<0.001). Younger age and delayed complete metabolic response were associated with lower chance of recurrence and death on univariate analysis. On multivariate analysis, delayed complete metabolic response remained significantly associated with no recurrence HR=0.14 (95% CI 0.25 to 0.84), p=0.031.Conclusions Survival outcome of patients with cervical cancer who show residual 18F-fluorodeoxyglucose uptake on initial PET/CT after treatment, but reach complete metabolic response on follow-up PET/CT, is not inferior compared with survival of patients who show complete metabolic response on initial PET/CT 3 months after treatment. Watchful waiting with follow-up PET/CT seems a safe option for these patients.