Adjuvant radiotherapy of endometrial cancer: role of 18F-FDG-PET/CT in treatment modulation

Objective : Residual disease after surgery is related to an unfavorable prognosis in patients with endometrial cancer (EC). An early diagnosis and treatment of this condition could improve patients’ outcome. Aim of this study was to define the role of postoperative 18 F-Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography ( 18 F-FDG-PET/CT) in patients with high risk of residual disease after EC surgery. Methods : Patients operated for EC, with one or more risk factors, who underwent 18 F-FDG-PET/CT before adjuvant treatment were included in this observational study. The primary endpoint was the rate of patients in whom 18 F-FDG-PET/CT changed the treatment strategy and/or the radiotherapy (RT) planning. Results : Our analysis included 58 patients (median age: 67.5 years, range: 48.0–86.0) with the following risk factors: lymphadenectomy not performed (26 patients; 44.8%), inadequate lymphadenectomy (23 patients; 39.7%), and high risk of residual disease due to advanced stage (nine patients; 15.5%). Postoperative 18 F-FDG-PET/CT imaging was positive in 18 patients (31%) in the following sites: pelvic extra-nodal disease (one patient), pelvic and/or paraaortic lymph nodes (12 patients), distant metastases (one patient), or combination of previous sites (four patients). Based on these results, the adjuvant therapeutic strategy was changed in five patients, three of whom were referred to chemotherapy alone due to distant metastases and two of whom were referred to nodal-directed treatment due to lymph node metastases (lymphadenectomy and pelvic chemoradiation plus boost, respectively). Furthermore, based on the 18 F-FDG-PET/CT results, the RT plan was modified in 13 patients (addition of a boost on residual pelvic/abdominal disease in 12 and target modification in one, respectively). Therefore, based on postoperative 18 F-FDG-PET/CT findings, the therapeutic strategy and the RT plan were changed in 5 patients (8.6%) and 13 patients (22.4%), respectively. Conclusion : In this analysis, the adjuvant treatment was modified after post-operative 18 F-FDG-PET/CT in about one third of patients. Further studies are needed to better define the risk factors (or their combinations) correlated with higher probability of residual disease after radical hysterectomy-adnexectomy for EC.