<sup>18</sup>FDG PET-CT significance for post-treatment monitoring in cervical and uterine cancer patients with suspected recurrence in previously irradiated zones

Abstract

Early detection of cervical (CC) and endometrial (EC) cancer recurrence in previously irradiated areas remains a difficult task for clinicians and radiologists. 18F-FDG PET-CT scope and limits in this matter are not clear yet.Purpose. To determine 18F-FDG PET-CT significance and diagnostic value in differential diagnosis of locoregional recurrence and post-radiation tissue changes in CC and EC patients with suspected relapse in preirradiated zones.Materials and methods. Follow-up data, including multiparametric MRI (T1-WI, T2-WI, DWI, DCE) and 18FFDG PET-CT full descriptions, were studied in 51pts., in 25(49%) CC and 26 (51%) EC Ia–IIIc FIGO, with suspected loco-regional recurrence in pre-irradiated area, 4–96 months after the end of treatment.Adjuvant combined radiotherapy (conformal pelvic EBRT – 3D-CRT, IMRT, VMAT, endovaginal 192Ir HDR brachytherapy) was performed in 33 (64,7%) pts. after radical surgery, adjuvant chemoradiation with Cisplatin 40 mg/m2 or Carboplatin AUC2 weekly – in 8 (24.2%) of them. 18 (35,3%) pts. were treated with definitive chemoradiation, median EQD2 for HR-CTV D90 81.6 ± 4.4 Gy (CI 95% 72.4 Gy – 93.7 Gy) and 54.6 ± 3.3 Gy (CI 95% 48.8–64.2 Gy) for metastatic pelvic and paraaortic lymph nodes.Indications for 18F-FDG PET-CT (Biograph True64, Siemens, 3.8–4.7 MBq/kg, total 169–356 MBq) in all pts. were suspicious clinical, cytological, complex ultrasound, and multiparametric MRI findings in pre-irradiated zones. Any areas of 18F-FDG pathologically increased uptake were considered hypermetabolic lesions, positive for cancer recurrence.Results. No evidence of loco-regional recurrence in pre-irradiated zones was confirmed in 32 (62.7%) pts. Clinical, morphological and radiological signs of progression were obtained in 16 (31.3%) 18F-FDG PET-CTpositive patients, with SUVmax 2.86–8.8 in this subgroup. 18F-FDG PET-CT false-positive results were obtained in 6 (11.8%) patients, false-negative – in 1 (1.9%) heavy pre-treated CC patient. 18F-FDG PET-CT sensitivity was 94.1%, specificity – 84.2%, positive predictive value – 72.7%, negative predictive value – 96.9%.Conclusions. 18F-FDG-PET-CT has a high diagnostic value in the differential diagnosis of loco-regional relapses and post-radiation tissue changes in CC and EC patients with suspected progression in pre-irradiated zones. But 18F-FDG-PET-CT findings evaluation and interpretation requires a multidisciplinary discussion and consensus for this cohort of patients.