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

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 SUV_max 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.

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