FDG-PET in the detection of recurrence of uterine cervical carcinoma following radiation therapy—tumor volume and FDG uptake value

Purpose.We evaluated the use of positron emission tomography (PET) with fluorine-18-labeled fluoro-2-deoxy-d-glucose (FDG) in follow-up study after radiation therapy in patients with uterine cervical carcinoma.Materials and methods.Thirty-two studies in 25 patients were reviewed. Twenty patients were treated with external beam irradiation and intracavitary brachytherapy, and five with irradiation following initial surgery. Time from initial treatment to FDG-PET was 23.3 (5.2–88.0) months. Rationale for FDG-PET was the presence of symptoms in 6 patients, abnormal serum tumor marker values in 13, abnormal lesions on other diagnostic imaging modalities in 19, and patient request in 2. On visualization of a lesion, the maximum standardized uptake value (maxSUV) of the lesion was calculated, and values over 2.0 were classified as FDG-positive. Maximum tumor diameter and tumor volume in the corresponding disease were estimated by computed tomography (CT) or magnetic resonance imaging (MRI).Results.Sensitivity and specificity of FDG-PET in the detection of recurrent disease were 91.5% (43/47) and 57.1% (4/7), respectively. Four false-negative findings were seen for small lung metastases having a volume less than 1 cm3. Three false-positive cases were a localized pneumonitis, a benign pubic bone fracture, and a fibrosis after interstitial brachytherapy. Sensitivity for extrapelvic lymph node metastases was extremely high (100%); in contrast, sensitivity and specificity for lung and bone lesions were 75.0% (12/16) and 33.3% (1/3), respectively. Regarding tumor volume measurement, good correlation between maxSUV on FDG-PET and tumor volume was obtained (lung metastases, P = 0.03; extrapelvic nodes, P < 0.0001). Within this study, all corresponding lesions over 1 cm3 showed a maxSUV value greater than 2.0.Conclusion.FDG-PET is a useful tool for the detection of extrapelvic lesions during the follow-up period after radiation therapy for cervical cancer. This study suggests that FDG uptake is associated with tumor volume, and FDG-PET has limitations in the detection of lesions less than 1 cm3 or microscopic disease. Careful diagnostic agreement between PET and CT/MRI for positive but benign lesions, such as inflammation and bone fracture, remains important.