Prognostic value of positron emission tomography using F-18-fluorodeoxyglucose in patients with cervical cancer undergoing radiotherapy

Objective. The purpose of this study was to determine whether positron emission tomography (PET) using F-18-fluorodeoxyglucose (FDG) before and after radiotherapy would predict whether local control of cervical cancer had been achieved. Methods. FDG-PET scans were performed prior to therapy and at a mean of 4.6 months after radiation in 20 patients (pts) with histologically proven uterine cervical cancer who were undergoing a "curative" course of radiation therapy. FDG uptake was interpreted visually by two readers using a 5-point grading system (0 = normal, 1 = probably normal, 2 = equivocal, 3 = probably abnormal, and 4 = definitely abnormal). The standardized uptake values corrected by lean body mass (SUL) were calculated for suspicious areas. The percentage of residual activity (%RA) for the posttherapy SUL was also evaluated as a percentage of the pretherapy SUL. Results. At baseline before irradiation, 17 of 20 (85.0%) primary tumors were detected. Following irradiation, no or low (grade 0-2) uptake was observed in 9 pts, and none of these had local recurrence. Among the remaining 11 pts with grade 3 or 4 uptake, the correct diagnosis was made for 5 pts with active tumor; SULs (mean ± SD = 4.17 ± 2.52) and %RAs (57.9 ± 16.8). Six patients without active tumor showed relatively low SULs (2.67 ± 0.69) and %RAs (43.0 ± 18.3). No significant differences were observed between the recurrent and nonrecurrent groups for these parameters. Overall, sensitivity, specificity, and accuracy were 100, 60, and 70%, respectively. Conclusion. These preliminary data indicate that FDG-PET is a sensitive tool for detecting active cervical cancer after radiation, however, the method, without anatomic correlation had suboptimal specificity.